turbojpeg.h

/*
 * Copyright (C)2009-2015, 2017, 2020-2021, 2023 D. R. Commander.
 *                                               All Rights Reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * - Redistributions of source code must retain the above copyright notice,
 *   this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright notice,
 *   this list of conditions and the following disclaimer in the documentation
 *   and/or other materials provided with the distribution.
 * - Neither the name of the libjpeg-turbo Project nor the names of its
 *   contributors may be used to endorse or promote products derived from this
 *   software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS",
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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 * ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE
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#ifndef __TURBOJPEG_H__
#define __TURBOJPEG_H__

#if defined(_WIN32) && defined(DLLDEFINE)
#define DLLEXPORT  __declspec(dllexport)
#else
#define DLLEXPORT
#endif
#define DLLCALL


/**
 * @addtogroup TurboJPEG
 * TurboJPEG API.  This API provides an interface for generating, decoding, and
 * transforming planar YUV and JPEG images in memory.
 *
 * @anchor YUVnotes
 * YUV Image Format Notes
 * ----------------------
 * Technically, the JPEG format uses the YCbCr colorspace (which is technically
 * not a colorspace but a color transform), but per the convention of the
 * digital video community, the TurboJPEG API uses "YUV" to refer to an image
 * format consisting of Y, Cb, and Cr image planes.
 *
 * Each plane is simply a 2D array of bytes, each byte representing the value
 * of one of the components (Y, Cb, or Cr) at a particular location in the
 * image.  The width and height of each plane are determined by the image
 * width, height, and level of chrominance subsampling.  The luminance plane
 * width is the image width padded to the nearest multiple of the horizontal
 * subsampling factor (1 in the case of 4:4:4, grayscale, or 4:4:0; 2 in the
 * case of 4:2:2 or 4:2:0; 4 in the case of 4:1:1.)  Similarly, the luminance
 * plane height is the image height padded to the nearest multiple of the
 * vertical subsampling factor (1 in the case of 4:4:4, 4:2:2, grayscale, or
 * 4:1:1; 2 in the case of 4:2:0 or 4:4:0.)  This is irrespective of any
 * additional padding that may be specified as an argument to the various YUV
 * functions.  The chrominance plane width is equal to the luminance plane
 * width divided by the horizontal subsampling factor, and the chrominance
 * plane height is equal to the luminance plane height divided by the vertical
 * subsampling factor.
 *
 * For example, if the source image is 35 x 35 pixels and 4:2:2 subsampling is
 * used, then the luminance plane would be 36 x 35 bytes, and each of the
 * chrominance planes would be 18 x 35 bytes.  If you specify a row alignment
 * of 4 bytes on top of this, then the luminance plane would be 36 x 35 bytes,
 * and each of the chrominance planes would be 20 x 35 bytes.
 *
 * @{
 */


/**
 * The number of chrominance subsampling options
 */
#define TJ_NUMSAMP  6

/**
 * Chrominance subsampling options.
 * When pixels are converted from RGB to YCbCr (see #TJCS_YCbCr) or from CMYK
 * to YCCK (see #TJCS_YCCK) as part of the JPEG compression process, some of
 * the Cb and Cr (chrominance) components can be discarded or averaged together
 * to produce a smaller image with little perceptible loss of image clarity.
 * (The human eye is more sensitive to small changes in brightness than to
 * small changes in color.)  This is called "chrominance subsampling".
 */
enum TJSAMP {
  /**
   * 4:4:4 chrominance subsampling (no chrominance subsampling).  The JPEG or
   * YUV image will contain one chrominance component for every pixel in the
   * source image.
   */
  TJSAMP_444 = 0,
  /**
   * 4:2:2 chrominance subsampling.  The JPEG or YUV image will contain one
   * chrominance component for every 2x1 block of pixels in the source image.
   */
  TJSAMP_422,
  /**
   * 4:2:0 chrominance subsampling.  The JPEG or YUV image will contain one
   * chrominance component for every 2x2 block of pixels in the source image.
   */
  TJSAMP_420,
  /**
   * Grayscale.  The JPEG or YUV image will contain no chrominance components.
   */
  TJSAMP_GRAY,
  /**
   * 4:4:0 chrominance subsampling.  The JPEG or YUV image will contain one
   * chrominance component for every 1x2 block of pixels in the source image.
   *
   * @note 4:4:0 subsampling is not fully accelerated in libjpeg-turbo.
   */
  TJSAMP_440,
  /**
   * 4:1:1 chrominance subsampling.  The JPEG or YUV image will contain one
   * chrominance component for every 4x1 block of pixels in the source image.
   * JPEG images compressed with 4:1:1 subsampling will be almost exactly the
   * same size as those compressed with 4:2:0 subsampling, and in the
   * aggregate, both subsampling methods produce approximately the same
   * perceptual quality.  However, 4:1:1 is better able to reproduce sharp
   * horizontal features.
   *
   * @note 4:1:1 subsampling is not fully accelerated in libjpeg-turbo.
   */
  TJSAMP_411
};

/**
 * MCU block width (in pixels) for a given level of chrominance subsampling.
 * MCU block sizes:
 * - 8x8 for no subsampling or grayscale
 * - 16x8 for 4:2:2
 * - 8x16 for 4:4:0
 * - 16x16 for 4:2:0
 * - 32x8 for 4:1:1
 */
static const int tjMCUWidth[TJ_NUMSAMP]  = { 8, 16, 16, 8, 8, 32 };

/**
 * MCU block height (in pixels) for a given level of chrominance subsampling.
 * MCU block sizes:
 * - 8x8 for no subsampling or grayscale
 * - 16x8 for 4:2:2
 * - 8x16 for 4:4:0
 * - 16x16 for 4:2:0
 * - 32x8 for 4:1:1
 */
static const int tjMCUHeight[TJ_NUMSAMP] = { 8, 8, 16, 8, 16, 8 };


/**
 * The number of pixel formats
 */
#define TJ_NUMPF  12

/**
 * Pixel formats
 */
enum TJPF {
  /**
   * RGB pixel format.  The red, green, and blue components in the image are
   * stored in 3-byte pixels in the order R, G, B from lowest to highest byte
   * address within each pixel.
   */
  TJPF_RGB = 0,
  /**
   * BGR pixel format.  The red, green, and blue components in the image are
   * stored in 3-byte pixels in the order B, G, R from lowest to highest byte
   * address within each pixel.
   */
  TJPF_BGR,
  /**
   * RGBX pixel format.  The red, green, and blue components in the image are
   * stored in 4-byte pixels in the order R, G, B from lowest to highest byte
   * address within each pixel.  The X component is ignored when compressing
   * and undefined when decompressing.
   */
  TJPF_RGBX,
  /**
   * BGRX pixel format.  The red, green, and blue components in the image are
   * stored in 4-byte pixels in the order B, G, R from lowest to highest byte
   * address within each pixel.  The X component is ignored when compressing
   * and undefined when decompressing.
   */
  TJPF_BGRX,
  /**
   * XBGR pixel format.  The red, green, and blue components in the image are
   * stored in 4-byte pixels in the order R, G, B from highest to lowest byte
   * address within each pixel.  The X component is ignored when compressing
   * and undefined when decompressing.
   */
  TJPF_XBGR,
  /**
   * XRGB pixel format.  The red, green, and blue components in the image are
   * stored in 4-byte pixels in the order B, G, R from highest to lowest byte
   * address within each pixel.  The X component is ignored when compressing
   * and undefined when decompressing.
   */
  TJPF_XRGB,
  /**
   * Grayscale pixel format.  Each 1-byte pixel represents a luminance
   * (brightness) level from 0 to 255.
   */
  TJPF_GRAY,
  /**
   * RGBA pixel format.  This is the same as @ref TJPF_RGBX, except that when
   * decompressing, the X component is guaranteed to be 0xFF, which can be
   * interpreted as an opaque alpha channel.
   */
  TJPF_RGBA,
  /**
   * BGRA pixel format.  This is the same as @ref TJPF_BGRX, except that when
   * decompressing, the X component is guaranteed to be 0xFF, which can be
   * interpreted as an opaque alpha channel.
   */
  TJPF_BGRA,
  /**
   * ABGR pixel format.  This is the same as @ref TJPF_XBGR, except that when
   * decompressing, the X component is guaranteed to be 0xFF, which can be
   * interpreted as an opaque alpha channel.
   */
  TJPF_ABGR,
  /**
   * ARGB pixel format.  This is the same as @ref TJPF_XRGB, except that when
   * decompressing, the X component is guaranteed to be 0xFF, which can be
   * interpreted as an opaque alpha channel.
   */
  TJPF_ARGB,
  /**
   * CMYK pixel format.  Unlike RGB, which is an additive color model used
   * primarily for display, CMYK (Cyan/Magenta/Yellow/Key) is a subtractive
   * color model used primarily for printing.  In the CMYK color model, the
   * value of each color component typically corresponds to an amount of cyan,
   * magenta, yellow, or black ink that is applied to a white background.  In
   * order to convert between CMYK and RGB, it is necessary to use a color
   * management system (CMS.)  A CMS will attempt to map colors within the
   * printer's gamut to perceptually similar colors in the display's gamut and
   * vice versa, but the mapping is typically not 1:1 or reversible, nor can it
   * be defined with a simple formula.  Thus, such a conversion is out of scope
   * for a codec library.  However, the TurboJPEG API allows for compressing
   * packed-pixel CMYK images into YCCK JPEG images (see #TJCS_YCCK) and
   * decompressing YCCK JPEG images into packed-pixel CMYK images.
   */
  TJPF_CMYK,
  /**
   * Unknown pixel format.  Currently this is only used by #tjLoadImage().
   */
  TJPF_UNKNOWN = -1
};

/**
 * Red offset (in bytes) for a given pixel format.  This specifies the number
 * of bytes that the red component is offset from the start of the pixel.  For
 * instance, if a pixel of format TJPF_BGRX is stored in
 * `unsigned char pixel[]`, then the red component will be
 *`pixel[tjRedOffset[TJPF_BGRX]]`.  This will be -1 if the pixel format does
 * not have a red component.
 */
static const int tjRedOffset[TJ_NUMPF] = {
  0, 2, 0, 2, 3, 1, -1, 0, 2, 3, 1, -1
};
/**
 * Green offset (in bytes) for a given pixel format.  This specifies the number
 * of bytes that the green component is offset from the start of the pixel.
 * For instance, if a pixel of format TJPF_BGRX is stored in
 * `unsigned char pixel[]`, then the green component will be
 * `pixel[tjGreenOffset[TJPF_BGRX]]`.  This will be -1 if the pixel format does
 * not have a green component.
 */
static const int tjGreenOffset[TJ_NUMPF] = {
  1, 1, 1, 1, 2, 2, -1, 1, 1, 2, 2, -1
};
/**
 * Blue offset (in bytes) for a given pixel format.  This specifies the number
 * of bytes that the blue component is offset from the start of the pixel.  For
 * instance, if a pixel of format TJPF_BGRX is stored in
 * `unsigned char pixel[]`, then the blue component will be
 * `pixel[tjBlueOffset[TJPF_BGRX]]`.  This will be -1 if the pixel format does
 * not have a blue component.
 */
static const int tjBlueOffset[TJ_NUMPF] = {
  2, 0, 2, 0, 1, 3, -1, 2, 0, 1, 3, -1
};
/**
 * Alpha offset (in bytes) for a given pixel format.  This specifies the number
 * of bytes that the alpha component is offset from the start of the pixel.
 * For instance, if a pixel of format TJPF_BGRA is stored in
 * `unsigned char pixel[]`, then the alpha component will be
 * `pixel[tjAlphaOffset[TJPF_BGRA]]`.  This will be -1 if the pixel format does
 * not have an alpha component.
 */
static const int tjAlphaOffset[TJ_NUMPF] = {
  -1, -1, -1, -1, -1, -1, -1, 3, 3, 0, 0, -1
};
/**
 * Pixel size (in bytes) for a given pixel format
 */
static const int tjPixelSize[TJ_NUMPF] = {
  3, 3, 4, 4, 4, 4, 1, 4, 4, 4, 4, 4
};


/**
 * The number of JPEG colorspaces
 */
#define TJ_NUMCS  5

/**
 * JPEG colorspaces
 */
enum TJCS {
  /**
   * RGB colorspace.  When compressing the JPEG image, the R, G, and B
   * components in the source image are reordered into image planes, but no
   * colorspace conversion or subsampling is performed.  RGB JPEG images can be
   * decompressed to packed-pixel images with any of the extended RGB or
   * grayscale pixel formats, but they cannot be decompressed to planar YUV
   * images.
   */
  TJCS_RGB = 0,
  /**
   * YCbCr colorspace.  YCbCr is not an absolute colorspace but rather a
   * mathematical transformation of RGB designed solely for storage and
   * transmission.  YCbCr images must be converted to RGB before they can
   * actually be displayed.  In the YCbCr colorspace, the Y (luminance)
   * component represents the black & white portion of the original image, and
   * the Cb and Cr (chrominance) components represent the color portion of the
   * original image.  Originally, the analog equivalent of this transformation
   * allowed the same signal to drive both black & white and color televisions,
   * but JPEG images use YCbCr primarily because it allows the color data to be
   * optionally subsampled for the purposes of reducing network or disk usage.
   * YCbCr is the most common JPEG colorspace, and YCbCr JPEG images can be
   * compressed from and decompressed to packed-pixel images with any of the
   * extended RGB or grayscale pixel formats.  YCbCr JPEG images can also be
   * compressed from and decompressed to planar YUV images.
   */
  TJCS_YCbCr,
  /**
   * Grayscale colorspace.  The JPEG image retains only the luminance data (Y
   * component), and any color data from the source image is discarded.
   * Grayscale JPEG images can be compressed from and decompressed to
   * packed-pixel images with any of the extended RGB or grayscale pixel
   * formats, or they can be compressed from and decompressed to planar YUV
   * images.
   */
  TJCS_GRAY,
  /**
   * CMYK colorspace.  When compressing the JPEG image, the C, M, Y, and K
   * components in the source image are reordered into image planes, but no
   * colorspace conversion or subsampling is performed.  CMYK JPEG images can
   * only be decompressed to packed-pixel images with the CMYK pixel format.
   */
  TJCS_CMYK,
  /**
   * YCCK colorspace.  YCCK (AKA "YCbCrK") is not an absolute colorspace but
   * rather a mathematical transformation of CMYK designed solely for storage
   * and transmission.  It is to CMYK as YCbCr is to RGB.  CMYK pixels can be
   * reversibly transformed into YCCK, and as with YCbCr, the chrominance
   * components in the YCCK pixels can be subsampled without incurring major
   * perceptual loss.  YCCK JPEG images can only be compressed from and
   * decompressed to packed-pixel images with the CMYK pixel format.
   */
  TJCS_YCCK
};


/**
 * Rows in the packed-pixel source/destination image are stored in bottom-up
 * (Windows, OpenGL) order rather than in top-down (X11) order.
 */
#define TJFLAG_BOTTOMUP  2
/**
 * When decompressing an image that was compressed using chrominance
 * subsampling, use the fastest chrominance upsampling algorithm available.
 * The default is to use smooth upsampling, which creates a smooth transition
 * between neighboring chrominance components in order to reduce upsampling
 * artifacts in the decompressed image.
 */
#define TJFLAG_FASTUPSAMPLE  256
/**
 * Disable JPEG buffer (re)allocation.  If passed to one of the JPEG
 * compression or transform functions, this flag will cause those functions to
 * generate an error if the JPEG destination buffer is invalid or too small,
 * rather than attempt to allocate or reallocate that buffer.
 */
#define TJFLAG_NOREALLOC  1024
/**
 * Use the fastest DCT/IDCT algorithm available.  The default if this flag is
 * not specified is implementation-specific.  For example, the implementation
 * of the TurboJPEG API in libjpeg-turbo uses the fast algorithm by default
 * when compressing, because this has been shown to have only a very slight
 * effect on accuracy, but it uses the accurate algorithm when decompressing,
 * because this has been shown to have a larger effect.
 */
#define TJFLAG_FASTDCT  2048
/**
 * Use the most accurate DCT/IDCT algorithm available.  The default if this
 * flag is not specified is implementation-specific.  For example, the
 * implementation of the TurboJPEG API in libjpeg-turbo uses the fast algorithm
 * by default when compressing, because this has been shown to have only a very
 * slight effect on accuracy, but it uses the accurate algorithm when
 * decompressing, because this has been shown to have a larger effect.
 */
#define TJFLAG_ACCURATEDCT  4096
/**
 * Immediately discontinue the current compression/decompression/transform
 * operation if a warning (non-fatal error) occurs.  The default behavior is to
 * allow the operation to complete unless a fatal error is encountered.
 */
#define TJFLAG_STOPONWARNING  8192
/**
 * Use progressive entropy coding in JPEG images generated by the compression
 * and transform functions.  Progressive entropy coding will generally improve
 * compression relative to baseline entropy coding (the default), but it will
 * reduce compression and decompression performance considerably.
 */
#define TJFLAG_PROGRESSIVE  16384
/**
 * Limit the number of progressive JPEG scans that the decompression and
 * transform functions will process.  If a progressive JPEG image contains an
 * unreasonably large number of scans, then this flag will cause the
 * decompression and transform functions to return an error.  The primary
 * purpose of this is to allow security-critical applications to guard against
 * an exploit of the progressive JPEG format described in
 * <a href="https://libjpeg-turbo.org/pmwiki/uploads/About/TwoIssueswiththeJPEGStandard.pdf" target="_blank">this report</a>.
 */
#define TJFLAG_LIMITSCANS  32768


/**
 * The number of error codes
 */
#define TJ_NUMERR  2

/**
 * Error codes
 */
enum TJERR {
  /**
   * The error was non-fatal and recoverable, but the destination image may
   * still be corrupt.
   */
  TJERR_WARNING = 0,
  /**
   * The error was fatal and non-recoverable.
   */
  TJERR_FATAL
};


/**
 * The number of transform operations
 */
#define TJ_NUMXOP  8

/**
 * Transform operations for #tjTransform()
 */
enum TJXOP {
  /**
   * Do not transform the position of the image pixels
   */
  TJXOP_NONE = 0,
  /**
   * Flip (mirror) image horizontally.  This transform is imperfect if there
   * are any partial MCU blocks on the right edge (see #TJXOPT_PERFECT.)
   */
  TJXOP_HFLIP,
  /**
   * Flip (mirror) image vertically.  This transform is imperfect if there are
   * any partial MCU blocks on the bottom edge (see #TJXOPT_PERFECT.)
   */
  TJXOP_VFLIP,
  /**
   * Transpose image (flip/mirror along upper left to lower right axis.)  This
   * transform is always perfect.
   */
  TJXOP_TRANSPOSE,
  /**
   * Transverse transpose image (flip/mirror along upper right to lower left
   * axis.)  This transform is imperfect if there are any partial MCU blocks in
   * the image (see #TJXOPT_PERFECT.)
   */
  TJXOP_TRANSVERSE,
  /**
   * Rotate image clockwise by 90 degrees.  This transform is imperfect if
   * there are any partial MCU blocks on the bottom edge (see
   * #TJXOPT_PERFECT.)
   */
  TJXOP_ROT90,
  /**
   * Rotate image 180 degrees.  This transform is imperfect if there are any
   * partial MCU blocks in the image (see #TJXOPT_PERFECT.)
   */
  TJXOP_ROT180,
  /**
   * Rotate image counter-clockwise by 90 degrees.  This transform is imperfect
   * if there are any partial MCU blocks on the right edge (see
   * #TJXOPT_PERFECT.)
   */
  TJXOP_ROT270
};


/**
 * This option will cause #tjTransform() to return an error if the transform is
 * not perfect.  Lossless transforms operate on MCU blocks, whose size depends
 * on the level of chrominance subsampling used (see #tjMCUWidth and
 * #tjMCUHeight.)  If the image's width or height is not evenly divisible by
 * the MCU block size, then there will be partial MCU blocks on the right
 * and/or bottom edges.  It is not possible to move these partial MCU blocks to
 * the top or left of the image, so any transform that would require that is
 * "imperfect."  If this option is not specified, then any partial MCU blocks
 * that cannot be transformed will be left in place, which will create
 * odd-looking strips on the right or bottom edge of the image.
 */
#define TJXOPT_PERFECT  1
/**
 * This option will cause #tjTransform() to discard any partial MCU blocks that
 * cannot be transformed.
 */
#define TJXOPT_TRIM  2
/**
 * This option will enable lossless cropping.  See #tjTransform() for more
 * information.
 */
#define TJXOPT_CROP  4
/**
 * This option will discard the color data in the source image and produce a
 * grayscale destination image.
 */
#define TJXOPT_GRAY  8
/**
 * This option will prevent #tjTransform() from outputting a JPEG image for
 * this particular transform.  (This can be used in conjunction with a custom
 * filter to capture the transformed DCT coefficients without transcoding
 * them.)
 */
#define TJXOPT_NOOUTPUT  16
/**
 * This option will enable progressive entropy coding in the JPEG image
 * generated by this particular transform.  Progressive entropy coding will
 * generally improve compression relative to baseline entropy coding (the
 * default), but it will reduce decompression performance considerably.
 */
#define TJXOPT_PROGRESSIVE  32
/**
 * This option will prevent #tjTransform() from copying any extra markers
 * (including EXIF and ICC profile data) from the source image to the
 * destination image.
 */
#define TJXOPT_COPYNONE  64


/**
 * Scaling factor
 */
typedef struct {
  /**
   * Numerator
   */
  int num;
  /**
   * Denominator
   */
  int denom;
} tjscalingfactor;

/**
 * Cropping region
 */
typedef struct {
  /**
   * The left boundary of the cropping region.  This must be evenly divisible
   * by the MCU block width (see #tjMCUWidth.)
   */
  int x;
  /**
   * The upper boundary of the cropping region.  This must be evenly divisible
   * by the MCU block height (see #tjMCUHeight.)
   */
  int y;
  /**
   * The width of the cropping region.  Setting this to 0 is the equivalent of
   * setting it to the width of the source JPEG image - x.
   */
  int w;
  /**
   * The height of the cropping region.  Setting this to 0 is the equivalent of
   * setting it to the height of the source JPEG image - y.
   */
  int h;
} tjregion;

/**
 * Lossless transform
 */
typedef struct tjtransform {
  /**
   * Cropping region
   */
  tjregion r;
  /**
   * One of the @ref TJXOP "transform operations"
   */
  int op;
  /**
   * The bitwise OR of one of more of the @ref TJXOPT_COPYNONE
   * "transform options"
   */
  int options;
  /**
   * Arbitrary data that can be accessed within the body of the callback
   * function
   */
  void *data;
  /**
   * A callback function that can be used to modify the DCT coefficients after
   * they are losslessly transformed but before they are transcoded to a new
   * JPEG image.  This allows for custom filters or other transformations to be
   * applied in the frequency domain.
   *
   * @param coeffs pointer to an array of transformed DCT coefficients.  (NOTE:
   * this pointer is not guaranteed to be valid once the callback returns, so
   * applications wishing to hand off the DCT coefficients to another function
   * or library should make a copy of them within the body of the callback.)
   *
   * @param arrayRegion #tjregion structure containing the width and height of
   * the array pointed to by `coeffs` as well as its offset relative to the
   * component plane.  TurboJPEG implementations may choose to split each
   * component plane into multiple DCT coefficient arrays and call the callback
   * function once for each array.
   *
   * @param planeRegion #tjregion structure containing the width and height of
   * the component plane to which `coeffs` belongs
   *
   * @param componentID ID number of the component plane to which `coeffs`
   * belongs.  (Y, Cb, and Cr have, respectively, ID's of 0, 1, and 2 in
   * typical JPEG images.)
   *
   * @param transformID ID number of the transformed image to which `coeffs`
   * belongs.  This is the same as the index of the transform in the
   * `transforms` array that was passed to #tjTransform().
   *
   * @param transform a pointer to a #tjtransform structure that specifies the
   * parameters and/or cropping region for this transform
   *
   * @return 0 if the callback was successful, or -1 if an error occurred.
   */
  int (*customFilter) (short *coeffs, tjregion arrayRegion,
                       tjregion planeRegion, int componentID, int transformID,
                       struct tjtransform *transform);
} tjtransform;

/**
 * TurboJPEG instance handle
 */
typedef void *tjhandle;


/**
 * Pad the given width to the nearest multiple of 4
 */
#define TJPAD(width)  (((width) + 3) & (~3))

/**
 * Compute the scaled value of `dimension` using the given scaling factor.
 * This macro performs the integer equivalent of `ceil(dimension *
 * scalingFactor)`.
 */
#define TJSCALED(dimension, scalingFactor) \
  (((dimension) * scalingFactor.num + scalingFactor.denom - 1) / \
   scalingFactor.denom)


#ifdef __cplusplus
extern "C" {
#endif


/**
 * Create a TurboJPEG compressor instance.
 *
 * @return a handle to the newly-created instance, or NULL if an error occurred
 * (see #tjGetErrorStr2().)
 */
DLLEXPORT tjhandle tjInitCompress(void);


/**
 * Compress a packed-pixel RGB, grayscale, or CMYK image into a JPEG image.
 *
 * @param handle a handle to a TurboJPEG compressor or transformer instance
 *
 * @param srcBuf pointer to a buffer containing a packed-pixel RGB, grayscale,
 * or CMYK source image to be compressed
 *
 * @param width width (in pixels) of the source image
 *
 * @param pitch bytes per row in the source image.  Normally this should be
 * <tt>width * #tjPixelSize[pixelFormat]</tt>, if the image is unpadded, or
 * <tt>#TJPAD(width * #tjPixelSize[pixelFormat])</tt> if each row of the image
 * is padded to the nearest multiple of 4 bytes, as is the case for Windows
 * bitmaps.  You can also be clever and use this parameter to skip rows, etc.
 * Setting this parameter to 0 is the equivalent of setting it to
 * <tt>width * #tjPixelSize[pixelFormat]</tt>.
 *
 * @param height height (in pixels) of the source image
 *
 * @param pixelFormat pixel format of the source image (see @ref TJPF
 * "Pixel formats".)
 *
 * @param jpegBuf address of a pointer to a byte buffer that will receive the
 * JPEG image.  TurboJPEG has the ability to reallocate the JPEG buffer to
 * accommodate the size of the JPEG image.  Thus, you can choose to:
 * -# pre-allocate the JPEG buffer with an arbitrary size using #tjAlloc() and
 * let TurboJPEG grow the buffer as needed,
 * -# set `*jpegBuf` to NULL to tell TurboJPEG to allocate the buffer for you,
 * or
 * -# pre-allocate the buffer to a "worst case" size determined by calling
 * #tjBufSize().  This should ensure that the buffer never has to be
 * re-allocated.  (Setting #TJFLAG_NOREALLOC guarantees that it won't be.)
 * .
 * If you choose option 1, then `*jpegSize` should be set to the size of your
 * pre-allocated buffer.  In any case, unless you have set #TJFLAG_NOREALLOC,
 * you should always check `*jpegBuf` upon return from this function, as it may
 * have changed.
 *
 * @param jpegSize pointer to an unsigned long variable that holds the size of
 * the JPEG buffer.  If `*jpegBuf` points to a pre-allocated buffer, then
 * `*jpegSize` should be set to the size of the buffer.  Upon return,
 * `*jpegSize` will contain the size of the JPEG image (in bytes.)  If
 * `*jpegBuf` points to a JPEG buffer that is being reused from a previous call
 * to one of the JPEG compression functions, then `*jpegSize` is ignored.
 *
 * @param jpegSubsamp the level of chrominance subsampling to be used when
 * generating the JPEG image (see @ref TJSAMP
 * "Chrominance subsampling options".)
 *
 * @param jpegQual the image quality of the generated JPEG image (1 = worst,
 * 100 = best)
 *
 * @param flags the bitwise OR of one or more of the @ref TJFLAG_ACCURATEDCT
 * "flags"
 *
 * @return 0 if successful, or -1 if an error occurred (see #tjGetErrorStr2()
 * and #tjGetErrorCode().)
 */
DLLEXPORT int tjCompress2(tjhandle handle, const unsigned char *srcBuf,
                          int width, int pitch, int height, int pixelFormat,
                          unsigned char **jpegBuf, unsigned long *jpegSize,
                          int jpegSubsamp, int jpegQual, int flags);


/**
 * Compress a unified planar YUV image into a JPEG image.
 *
 * @param handle a handle to a TurboJPEG compressor or transformer instance
 *
 * @param srcBuf pointer to a buffer containing a unified planar YUV source
 * image to be compressed.  The size of this buffer should match the value
 * returned by #tjBufSizeYUV2() for the given image width, height, row
 * alignment, and level of chrominance subsampling.  The Y, U (Cb), and V (Cr)
 * image planes should be stored sequentially in the buffer.  (Refer to
 * @ref YUVnotes "YUV Image Format Notes".)
 *
 * @param width width (in pixels) of the source image.  If the width is not an
 * even multiple of the MCU block width (see #tjMCUWidth), then an intermediate
 * buffer copy will be performed.
 *
 * @param align row alignment (in bytes) of the source image (must be a power
 * of 2.)  Setting this parameter to n indicates that each row in each plane of
 * the source image is padded to the nearest multiple of n bytes
 * (1 = unpadded.)
 *
 * @param height height (in pixels) of the source image.  If the height is not
 * an even multiple of the MCU block height (see #tjMCUHeight), then an
 * intermediate buffer copy will be performed.
 *
 * @param subsamp the level of chrominance subsampling used in the source image
 * (see @ref TJSAMP "Chrominance subsampling options".)
 *
 * @param jpegBuf address of a pointer to a byte buffer that will receive the
 * JPEG image.  TurboJPEG has the ability to reallocate the JPEG buffer to
 * accommodate the size of the JPEG image.  Thus, you can choose to:
 * -# pre-allocate the JPEG buffer with an arbitrary size using #tjAlloc() and
 * let TurboJPEG grow the buffer as needed,
 * -# set `*jpegBuf` to NULL to tell TurboJPEG to allocate the buffer for you,
 * or
 * -# pre-allocate the buffer to a "worst case" size determined by calling
 * #tjBufSize().  This should ensure that the buffer never has to be
 * re-allocated.  (Setting #TJFLAG_NOREALLOC guarantees that it won't be.)
 * .
 * If you choose option 1, then `*jpegSize` should be set to the size of your
 * pre-allocated buffer.  In any case, unless you have set #TJFLAG_NOREALLOC,
 * you should always check `*jpegBuf` upon return from this function, as it may
 * have changed.
 *
 * @param jpegSize pointer to an unsigned long variable that holds the size of
 * the JPEG buffer.  If `*jpegBuf` points to a pre-allocated buffer, then
 * `*jpegSize` should be set to the size of the buffer.  Upon return,
 * `*jpegSize` will contain the size of the JPEG image (in bytes.)  If
 * `*jpegBuf` points to a JPEG buffer that is being reused from a previous call
 * to one of the JPEG compression functions, then `*jpegSize` is ignored.
 *
 * @param jpegQual the image quality of the generated JPEG image (1 = worst,
 * 100 = best)
 *
 * @param flags the bitwise OR of one or more of the @ref TJFLAG_ACCURATEDCT
 * "flags"
 *
 * @return 0 if successful, or -1 if an error occurred (see #tjGetErrorStr2()
 * and #tjGetErrorCode().)
 */
DLLEXPORT int tjCompressFromYUV(tjhandle handle, const unsigned char *srcBuf,
                                int width, int align, int height, int subsamp,
                                unsigned char **jpegBuf,
                                unsigned long *jpegSize, int jpegQual,
                                int flags);


/**
 * Compress a set of Y, U (Cb), and V (Cr) image planes into a JPEG image.
 *
 * @param handle a handle to a TurboJPEG compressor or transformer instance
 *
 * @param srcPlanes an array of pointers to Y, U (Cb), and V (Cr) image planes
 * (or just a Y plane, if compressing a grayscale image) that contain a YUV
 * source image to be compressed.  These planes can be contiguous or
 * non-contiguous in memory.  The size of each plane should match the value
 * returned by #tjPlaneSizeYUV() for the given image width, height, strides,
 * and level of chrominance subsampling.  Refer to @ref YUVnotes
 * "YUV Image Format Notes" for more details.
 *
 * @param width width (in pixels) of the source image.  If the width is not an
 * even multiple of the MCU block width (see #tjMCUWidth), then an intermediate
 * buffer copy will be performed.
 *
 * @param strides an array of integers, each specifying the number of bytes per
 * row in the corresponding plane of the YUV source image.  Setting the stride
 * for any plane to 0 is the same as setting it to the plane width (see
 * @ref YUVnotes "YUV Image Format Notes".)  If `strides` is NULL, then the
 * strides for all planes will be set to their respective plane widths.  You
 * can adjust the strides in order to specify an arbitrary amount of row
 * padding in each plane or to create a JPEG image from a subregion of a larger
 * planar YUV image.
 *
 * @param height height (in pixels) of the source image.  If the height is not
 * an even multiple of the MCU block height (see #tjMCUHeight), then an
 * intermediate buffer copy will be performed.
 *
 * @param subsamp the level of chrominance subsampling used in the source image
 * (see @ref TJSAMP "Chrominance subsampling options".)
 *
 * @param jpegBuf address of a pointer to a byte buffer that will receive the
 * JPEG image.  TurboJPEG has the ability to reallocate the JPEG buffer to
 * accommodate the size of the JPEG image.  Thus, you can choose to:
 * -# pre-allocate the JPEG buffer with an arbitrary size using #tjAlloc() and
 * let TurboJPEG grow the buffer as needed,
 * -# set `*jpegBuf` to NULL to tell TurboJPEG to allocate the buffer for you,
 * or
 * -# pre-allocate the buffer to a "worst case" size determined by calling
 * #tjBufSize().  This should ensure that the buffer never has to be
 * re-allocated.  (Setting #TJFLAG_NOREALLOC guarantees that it won't be.)
 * .
 * If you choose option 1, then `*jpegSize` should be set to the size of your
 * pre-allocated buffer.  In any case, unless you have set #TJFLAG_NOREALLOC,
 * you should always check `*jpegBuf` upon return from this function, as it may
 * have changed.
 *
 * @param jpegSize pointer to an unsigned long variable that holds the size of
 * the JPEG buffer.  If `*jpegBuf` points to a pre-allocated buffer, then
 * `*jpegSize` should be set to the size of the buffer.  Upon return,
 * `*jpegSize` will contain the size of the JPEG image (in bytes.)  If
 * `*jpegBuf` points to a JPEG buffer that is being reused from a previous call
 * to one of the JPEG compression functions, then `*jpegSize` is ignored.
 *
 * @param jpegQual the image quality of the generated JPEG image (1 = worst,
 * 100 = best)
 *
 * @param flags the bitwise OR of one or more of the @ref TJFLAG_ACCURATEDCT
 * "flags"
 *
 * @return 0 if successful, or -1 if an error occurred (see #tjGetErrorStr2()
 * and #tjGetErrorCode().)
 */
DLLEXPORT int tjCompressFromYUVPlanes(tjhandle handle,
                                      const unsigned char **srcPlanes,
                                      int width, const int *strides,
                                      int height, int subsamp,
                                      unsigned char **jpegBuf,
                                      unsigned long *jpegSize, int jpegQual,
                                      int flags);


/**
 * The maximum size of the buffer (in bytes) required to hold a JPEG image with
 * the given parameters.  The number of bytes returned by this function is
 * larger than the size of the uncompressed source image.  The reason for this
 * is that the JPEG format uses 16-bit coefficients, so it is possible for a
 * very high-quality source image with very high-frequency content to expand
 * rather than compress when converted to the JPEG format.  Such images
 * represent very rare corner cases, but since there is no way to predict the
 * size of a JPEG image prior to compression, the corner cases have to be
 * handled.
 *
 * @param width width (in pixels) of the image
 *
 * @param height height (in pixels) of the image
 *
 * @param jpegSubsamp the level of chrominance subsampling to be used when
 * generating the JPEG image (see @ref TJSAMP
 * "Chrominance subsampling options".)
 *
 * @return the maximum size of the buffer (in bytes) required to hold the
 * image, or -1 if the arguments are out of bounds.
 */
DLLEXPORT unsigned long tjBufSize(int width, int height, int jpegSubsamp);


/**
 * The size of the buffer (in bytes) required to hold a unified planar YUV
 * image with the given parameters.
 *
 * @param width width (in pixels) of the image
 *
 * @param align row alignment (in bytes) of the image (must be a power of 2.)
 * Setting this parameter to n specifies that each row in each plane of the
 * image will be padded to the nearest multiple of n bytes (1 = unpadded.)
 *
 * @param height height (in pixels) of the image
 *
 * @param subsamp level of chrominance subsampling in the image (see
 * @ref TJSAMP "Chrominance subsampling options".)
 *
 * @return the size of the buffer (in bytes) required to hold the image, or -1
 * if the arguments are out of bounds.
 */
DLLEXPORT unsigned long tjBufSizeYUV2(int width, int align, int height,
                                      int subsamp);


/**
 * The size of the buffer (in bytes) required to hold a YUV image plane with
 * the given parameters.
 *
 * @param componentID ID number of the image plane (0 = Y, 1 = U/Cb, 2 = V/Cr)
 *
 * @param width width (in pixels) of the YUV image.  NOTE: this is the width of
 * the whole image, not the plane width.
 *
 * @param stride bytes per row in the image plane.  Setting this to 0 is the
 * equivalent of setting it to the plane width.
 *
 * @param height height (in pixels) of the YUV image.  NOTE: this is the height
 * of the whole image, not the plane height.
 *
 * @param subsamp level of chrominance subsampling in the image (see
 * @ref TJSAMP "Chrominance subsampling options".)
 *
 * @return the size of the buffer (in bytes) required to hold the YUV image
 * plane, or -1 if the arguments are out of bounds.
 */
DLLEXPORT unsigned long tjPlaneSizeYUV(int componentID, int width, int stride,
                                       int height, int subsamp);


/**
 * The plane width of a YUV image plane with the given parameters.  Refer to
 * @ref YUVnotes "YUV Image Format Notes" for a description of plane width.
 *
 * @param componentID ID number of the image plane (0 = Y, 1 = U/Cb, 2 = V/Cr)
 *
 * @param width width (in pixels) of the YUV image
 *
 * @param subsamp level of chrominance subsampling in the image (see
 * @ref TJSAMP "Chrominance subsampling options".)
 *
 * @return the plane width of a YUV image plane with the given parameters, or
 * -1 if the arguments are out of bounds.
 */
DLLEXPORT int tjPlaneWidth(int componentID, int width, int subsamp);


/**
 * The plane height of a YUV image plane with the given parameters.  Refer to
 * @ref YUVnotes "YUV Image Format Notes" for a description of plane height.
 *
 * @param componentID ID number of the image plane (0 = Y, 1 = U/Cb, 2 = V/Cr)
 *
 * @param height height (in pixels) of the YUV image
 *
 * @param subsamp level of chrominance subsampling in the image (see
 * @ref TJSAMP "Chrominance subsampling options".)
 *
 * @return the plane height of a YUV image plane with the given parameters, or
 * -1 if the arguments are out of bounds.
 */
DLLEXPORT int tjPlaneHeight(int componentID, int height, int subsamp);


/**
 * Encode a packed-pixel RGB or grayscale image into a unified planar YUV
 * image.  This function performs color conversion (which is accelerated in the
 * libjpeg-turbo implementation) but does not execute any of the other steps in
 * the JPEG compression process.
 *
 * @param handle a handle to a TurboJPEG compressor or transformer instance
 *
 * @param srcBuf pointer to a buffer containing a packed-pixel RGB or grayscale
 * source image to be encoded
 *
 * @param width width (in pixels) of the source image
 *
 * @param pitch bytes per row in the source image.  Normally this should be
 * <tt>width * #tjPixelSize[pixelFormat]</tt>, if the image is unpadded, or
 * <tt>#TJPAD(width * #tjPixelSize[pixelFormat])</tt> if each row of the image
 * is padded to the nearest multiple of 4 bytes, as is the case for Windows
 * bitmaps.  You can also be clever and use this parameter to skip rows, etc.
 * Setting this parameter to 0 is the equivalent of setting it to
 * <tt>width * #tjPixelSize[pixelFormat]</tt>.
 *
 * @param height height (in pixels) of the source image
 *
 * @param pixelFormat pixel format of the source image (see @ref TJPF
 * "Pixel formats".)
 *
 * @param dstBuf pointer to a buffer that will receive the unified planar YUV
 * image.  Use #tjBufSizeYUV2() to determine the appropriate size for this
 * buffer based on the image width, height, row alignment, and level of
 * chrominance subsampling.  The Y, U (Cb), and V (Cr) image planes will be
 * stored sequentially in the buffer.  (Refer to @ref YUVnotes
 * "YUV Image Format Notes".)
 *
 * @param align row alignment (in bytes) of the YUV image (must be a power of
 * 2.)  Setting this parameter to n will cause each row in each plane of the
 * YUV image to be padded to the nearest multiple of n bytes (1 = unpadded.)
 * To generate images suitable for X Video, `align` should be set to 4.
 *
 * @param subsamp the level of chrominance subsampling to be used when
 * generating the YUV image (see @ref TJSAMP
 * "Chrominance subsampling options".)  To generate images suitable for X
 * Video, `subsamp` should be set to @ref TJSAMP_420.  This produces an image
 * compatible with the I420 (AKA "YUV420P") format.
 *
 * @param flags the bitwise OR of one or more of the @ref TJFLAG_ACCURATEDCT
 * "flags"
 *
 * @return 0 if successful, or -1 if an error occurred (see #tjGetErrorStr2()
 * and #tjGetErrorCode().)
 */
DLLEXPORT int tjEncodeYUV3(tjhandle handle, const unsigned char *srcBuf,
                           int width, int pitch, int height, int pixelFormat,
                           unsigned char *dstBuf, int align, int subsamp,
                           int flags);


/**
 * Encode a packed-pixel RGB or grayscale image into separate Y, U (Cb), and
 * V (Cr) image planes.  This function performs color conversion (which is
 * accelerated in the libjpeg-turbo implementation) but does not execute any of
 * the other steps in the JPEG compression process.
 *
 * @param handle a handle to a TurboJPEG compressor or transformer instance
 *
 * @param srcBuf pointer to a buffer containing a packed-pixel RGB or grayscale
 * source image to be encoded
 *
 * @param width width (in pixels) of the source image
 *
 * @param pitch bytes per row in the source image.  Normally this should be
 * <tt>width * #tjPixelSize[pixelFormat]</tt>, if the image is unpadded, or
 * <tt>#TJPAD(width * #tjPixelSize[pixelFormat])</tt> if each row of the image
 * is padded to the nearest multiple of 4 bytes, as is the case for Windows
 * bitmaps.  You can also be clever and use this parameter to skip rows, etc.
 * Setting this parameter to 0 is the equivalent of setting it to
 * <tt>width * #tjPixelSize[pixelFormat]</tt>.
 *
 * @param height height (in pixels) of the source image
 *
 * @param pixelFormat pixel format of the source image (see @ref TJPF
 * "Pixel formats".)
 *
 * @param dstPlanes an array of pointers to Y, U (Cb), and V (Cr) image planes
 * (or just a Y plane, if generating a grayscale image) that will receive the
 * encoded image.  These planes can be contiguous or non-contiguous in memory.
 * Use #tjPlaneSizeYUV() to determine the appropriate size for each plane based
 * on the image width, height, strides, and level of chrominance subsampling.
 * Refer to @ref YUVnotes "YUV Image Format Notes" for more details.
 *
 * @param strides an array of integers, each specifying the number of bytes per
 * row in the corresponding plane of the YUV image.  Setting the stride for any
 * plane to 0 is the same as setting it to the plane width (see @ref YUVnotes
 * "YUV Image Format Notes".)  If `strides` is NULL, then the strides for all
 * planes will be set to their respective plane widths.  You can adjust the
 * strides in order to add an arbitrary amount of row padding to each plane or
 * to encode an RGB or grayscale image into a subregion of a larger planar YUV
 * image.
 *
 * @param subsamp the level of chrominance subsampling to be used when
 * generating the YUV image (see @ref TJSAMP
 * "Chrominance subsampling options".)  To generate images suitable for X
 * Video, `subsamp` should be set to @ref TJSAMP_420.  This produces an image
 * compatible with the I420 (AKA "YUV420P") format.
 *
 * @param flags the bitwise OR of one or more of the @ref TJFLAG_ACCURATEDCT
 * "flags"
 *
 * @return 0 if successful, or -1 if an error occurred (see #tjGetErrorStr2()
 * and #tjGetErrorCode().)
 */
DLLEXPORT int tjEncodeYUVPlanes(tjhandle handle, const unsigned char *srcBuf,
                                int width, int pitch, int height,
                                int pixelFormat, unsigned char **dstPlanes,
                                int *strides, int subsamp, int flags);


/**
 * Create a TurboJPEG decompressor instance.
 *
 * @return a handle to the newly-created instance, or NULL if an error occurred
 * (see #tjGetErrorStr2().)
 */
DLLEXPORT tjhandle tjInitDecompress(void);


/**
 * Retrieve information about a JPEG image without decompressing it, or prime
 * the decompressor with quantization and Huffman tables.
 *
 * @param handle a handle to a TurboJPEG decompressor or transformer instance
 *
 * @param jpegBuf pointer to a byte buffer containing a JPEG image or an
 * "abbreviated table specification" (AKA "tables-only") datastream.  Passing a
 * tables-only datastream to this function primes the decompressor with
 * quantization and Huffman tables that can be used when decompressing
 * subsequent "abbreviated image" datastreams.  This is useful, for instance,
 * when decompressing video streams in which all frames share the same
 * quantization and Huffman tables.
 *
 * @param jpegSize size of the JPEG image or tables-only datastream (in bytes)
 *
 * @param width pointer to an integer variable that will receive the width (in
 * pixels) of the JPEG image.  If `jpegBuf` points to a tables-only datastream,
 * then `width` is ignored.
 *
 * @param height pointer to an integer variable that will receive the height
 * (in pixels) of the JPEG image.  If `jpegBuf` points to a tables-only
 * datastream, then `height` is ignored.
 *
 * @param jpegSubsamp pointer to an integer variable that will receive the
 * level of chrominance subsampling used when the JPEG image was compressed
 * (see @ref TJSAMP "Chrominance subsampling options".)  If `jpegBuf` points to
 * a tables-only datastream, then `jpegSubsamp` is ignored.
 *
 * @param jpegColorspace pointer to an integer variable that will receive one
 * of the JPEG colorspace constants, indicating the colorspace of the JPEG
 * image (see @ref TJCS "JPEG colorspaces".)  If `jpegBuf` points to a
 * tables-only datastream, then `jpegColorspace` is ignored.
 *
 * @return 0 if successful, or -1 if an error occurred (see #tjGetErrorStr2()
 * and #tjGetErrorCode().)
 */
DLLEXPORT int tjDecompressHeader3(tjhandle handle,
                                  const unsigned char *jpegBuf,
                                  unsigned long jpegSize, int *width,
                                  int *height, int *jpegSubsamp,
                                  int *jpegColorspace);


/**
 * Returns a list of fractional scaling factors that the JPEG decompressor
 * supports.
 *
 * @param numScalingFactors pointer to an integer variable that will receive
 * the number of elements in the list
 *
 * @return a pointer to a list of fractional scaling factors, or NULL if an
 * error is encountered (see #tjGetErrorStr2().)
 */
DLLEXPORT tjscalingfactor *tjGetScalingFactors(int *numScalingFactors);


/**
 * Decompress a JPEG image into a packed-pixel RGB, grayscale, or CMYK image.
 *
 * @param handle a handle to a TurboJPEG decompressor or transformer instance
 *
 * @param jpegBuf pointer to a byte buffer containing the JPEG image to
 * decompress
 *
 * @param jpegSize size of the JPEG image (in bytes)
 *
 * @param dstBuf pointer to a buffer that will receive the packed-pixel
 * decompressed image.  This buffer should normally be `pitch * scaledHeight`
 * bytes in size, where `scaledHeight` can be determined by calling #TJSCALED()
 * with the JPEG image height and one of the scaling factors returned by
 * #tjGetScalingFactors().  The `dstBuf` pointer may also be used to decompress
 * into a specific region of a larger buffer.
 *
 * @param width desired width (in pixels) of the destination image.  If this is
 * different than the width of the JPEG image being decompressed, then
 * TurboJPEG will use scaling in the JPEG decompressor to generate the largest
 * possible image that will fit within the desired width.  If `width` is set to
 * 0, then only the height will be considered when determining the scaled image
 * size.
 *
 * @param pitch bytes per row in the destination image.  Normally this should
 * be set to <tt>scaledWidth * #tjPixelSize[pixelFormat]</tt>, if the
 * destination image should be unpadded, or
 * <tt>#TJPAD(scaledWidth * #tjPixelSize[pixelFormat])</tt> if each row of the
 * destination image should be padded to the nearest multiple of 4 bytes, as is
 * the case for Windows bitmaps.  (NOTE: `scaledWidth` can be determined by
 * calling #TJSCALED() with the JPEG image width and one of the scaling factors
 * returned by #tjGetScalingFactors().)  You can also be clever and use the
 * pitch parameter to skip rows, etc.  Setting this parameter to 0 is the
 * equivalent of setting it to
 * <tt>scaledWidth * #tjPixelSize[pixelFormat]</tt>.
 *
 * @param height desired height (in pixels) of the destination image.  If this
 * is different than the height of the JPEG image being decompressed, then
 * TurboJPEG will use scaling in the JPEG decompressor to generate the largest
 * possible image that will fit within the desired height.  If `height` is set
 * to 0, then only the width will be considered when determining the scaled
 * image size.
 *
 * @param pixelFormat pixel format of the destination image (see @ref
 * TJPF "Pixel formats".)
 *
 * @param flags the bitwise OR of one or more of the @ref TJFLAG_ACCURATEDCT
 * "flags"
 *
 * @return 0 if successful, or -1 if an error occurred (see #tjGetErrorStr2()
 * and #tjGetErrorCode().)
 */
DLLEXPORT int tjDecompress2(tjhandle handle, const unsigned char *jpegBuf,
                            unsigned long jpegSize, unsigned char *dstBuf,
                            int width, int pitch, int height, int pixelFormat,
                            int flags);


/**
 * Decompress a JPEG image into a unified planar YUV image.  This function
 * performs JPEG decompression but leaves out the color conversion step, so a
 * planar YUV image is generated instead of a packed-pixel image.
 *
 * @param handle a handle to a TurboJPEG decompressor or transformer instance
 *
 * @param jpegBuf pointer to a byte buffer containing the JPEG image to
 * decompress
 *
 * @param jpegSize size of the JPEG image (in bytes)
 *
 * @param dstBuf pointer to a buffer that will receive the unified planar YUV
 * decompressed image.  Use #tjBufSizeYUV2() to determine the appropriate size
 * for this buffer based on the scaled image width, scaled image height, row
 * alignment, and level of chrominance subsampling.  The Y, U (Cb), and V (Cr)
 * image planes will be stored sequentially in the buffer.  (Refer to
 * @ref YUVnotes "YUV Image Format Notes".)
 *
 * @param width desired width (in pixels) of the YUV image.  If this is
 * different than the width of the JPEG image being decompressed, then
 * TurboJPEG will use scaling in the JPEG decompressor to generate the largest
 * possible image that will fit within the desired width.  If `width` is set to
 * 0, then only the height will be considered when determining the scaled image
 * size.  If the scaled width is not an even multiple of the MCU block width
 * (see #tjMCUWidth), then an intermediate buffer copy will be performed.
 *
 * @param align row alignment (in bytes) of the YUV image (must be a power of
 * 2.)  Setting this parameter to n will cause each row in each plane of the
 * YUV image to be padded to the nearest multiple of n bytes (1 = unpadded.)
 * To generate images suitable for X Video, `align` should be set to 4.
 *
 * @param height desired height (in pixels) of the YUV image.  If this is
 * different than the height of the JPEG image being decompressed, then
 * TurboJPEG will use scaling in the JPEG decompressor to generate the largest
 * possible image that will fit within the desired height.  If `height` is set
 * to 0, then only the width will be considered when determining the scaled
 * image size.  If the scaled height is not an even multiple of the MCU block
 * height (see #tjMCUHeight), then an intermediate buffer copy will be
 * performed.
 *
 * @param flags the bitwise OR of one or more of the @ref TJFLAG_ACCURATEDCT
 * "flags"
 *
 * @return 0 if successful, or -1 if an error occurred (see #tjGetErrorStr2()
 * and #tjGetErrorCode().)
 */
DLLEXPORT int tjDecompressToYUV2(tjhandle handle, const unsigned char *jpegBuf,
                                 unsigned long jpegSize, unsigned char *dstBuf,
                                 int width, int align, int height, int flags);


/**
 * Decompress a JPEG image into separate Y, U (Cb), and V (Cr) image
 * planes.  This function performs JPEG decompression but leaves out the color
 * conversion step, so a planar YUV image is generated instead of a
 * packed-pixel image.
 *
 * @param handle a handle to a TurboJPEG decompressor or transformer instance
 *
 * @param jpegBuf pointer to a byte buffer containing the JPEG image to
 * decompress
 *
 * @param jpegSize size of the JPEG image (in bytes)
 *
 * @param dstPlanes an array of pointers to Y, U (Cb), and V (Cr) image planes
 * (or just a Y plane, if decompressing a grayscale image) that will receive
 * the decompressed image.  These planes can be contiguous or non-contiguous in
 * memory.  Use #tjPlaneSizeYUV() to determine the appropriate size for each
 * plane based on the scaled image width, scaled image height, strides, and
 * level of chrominance subsampling.  Refer to @ref YUVnotes
 * "YUV Image Format Notes" for more details.
 *
 * @param width desired width (in pixels) of the YUV image.  If this is
 * different than the width of the JPEG image being decompressed, then
 * TurboJPEG will use scaling in the JPEG decompressor to generate the largest
 * possible image that will fit within the desired width.  If `width` is set to
 * 0, then only the height will be considered when determining the scaled image
 * size.  If the scaled width is not an even multiple of the MCU block width
 * (see #tjMCUWidth), then an intermediate buffer copy will be performed.
 *
 * @param strides an array of integers, each specifying the number of bytes per
 * row in the corresponding plane of the YUV image.  Setting the stride for any
 * plane to 0 is the same as setting it to the scaled plane width (see
 * @ref YUVnotes "YUV Image Format Notes".)  If `strides` is NULL, then the
 * strides for all planes will be set to their respective scaled plane widths.
 * You can adjust the strides in order to add an arbitrary amount of row
 * padding to each plane or to decompress the JPEG image into a subregion of a
 * larger planar YUV image.
 *
 * @param height desired height (in pixels) of the YUV image.  If this is
 * different than the height of the JPEG image being decompressed, then
 * TurboJPEG will use scaling in the JPEG decompressor to generate the largest
 * possible image that will fit within the desired height.  If `height` is set
 * to 0, then only the width will be considered when determining the scaled
 * image size.  If the scaled height is not an even multiple of the MCU block
 * height (see #tjMCUHeight), then an intermediate buffer copy will be
 * performed.
 *
 * @param flags the bitwise OR of one or more of the @ref TJFLAG_ACCURATEDCT
 * "flags"
 *
 * @return 0 if successful, or -1 if an error occurred (see #tjGetErrorStr2()
 * and #tjGetErrorCode().)
 */
DLLEXPORT int tjDecompressToYUVPlanes(tjhandle handle,
                                      const unsigned char *jpegBuf,
                                      unsigned long jpegSize,
                                      unsigned char **dstPlanes, int width,
                                      int *strides, int height, int flags);


/**
 * Decode a unified planar YUV image into a packed-pixel RGB or grayscale
 * image.  This function performs color conversion (which is accelerated in the
 * libjpeg-turbo implementation) but does not execute any of the other steps in
 * the JPEG decompression process.
 *
 * @param handle a handle to a TurboJPEG decompressor or transformer instance
 *
 * @param srcBuf pointer to a buffer containing a unified planar YUV source
 * image to be decoded.  The size of this buffer should match the value
 * returned by #tjBufSizeYUV2() for the given image width, height, row
 * alignment, and level of chrominance subsampling.  The Y, U (Cb), and V (Cr)
 * image planes should be stored sequentially in the source buffer.  (Refer to
 * @ref YUVnotes "YUV Image Format Notes".)
 *
 * @param align row alignment (in bytes) of the YUV source image (must be a
 * power of 2.)  Setting this parameter to n indicates that each row in each
 * plane of the YUV source image is padded to the nearest multiple of n bytes
 * (1 = unpadded.)
 *
 * @param subsamp the level of chrominance subsampling used in the YUV source
 * image (see @ref TJSAMP "Chrominance subsampling options".)
 *
 * @param dstBuf pointer to a buffer that will receive the packed-pixel decoded
 * image.  This buffer should normally be `pitch * height` bytes in size, but
 * the `dstBuf` pointer can also be used to decode into a specific region of a
 * larger buffer.
 *
 * @param width width (in pixels) of the source and destination images
 *
 * @param pitch bytes per row in the destination image.  Normally this should
 * be set to <tt>width * #tjPixelSize[pixelFormat]</tt>, if the destination
 * image should be unpadded, or
 * <tt>#TJPAD(width * #tjPixelSize[pixelFormat])</tt> if each row of the
 * destination image should be padded to the nearest multiple of 4 bytes, as is
 * the case for Windows bitmaps.  You can also be clever and use the pitch
 * parameter to skip rows, etc.  Setting this parameter to 0 is the equivalent
 * of setting it to <tt>width * #tjPixelSize[pixelFormat]</tt>.
 *
 * @param height height (in pixels) of the source and destination images
 *
 * @param pixelFormat pixel format of the destination image (see @ref TJPF
 * "Pixel formats".)
 *
 * @param flags the bitwise OR of one or more of the @ref TJFLAG_ACCURATEDCT
 * "flags"
 *
 * @return 0 if successful, or -1 if an error occurred (see #tjGetErrorStr2()
 * and #tjGetErrorCode().)
 */
DLLEXPORT int tjDecodeYUV(tjhandle handle, const unsigned char *srcBuf,
                          int align, int subsamp, unsigned char *dstBuf,
                          int width, int pitch, int height, int pixelFormat,
                          int flags);


/**
 * Decode a set of Y, U (Cb), and V (Cr) image planes into a packed-pixel RGB
 * or grayscale image.  This function performs color conversion (which is
 * accelerated in the libjpeg-turbo implementation) but does not execute any of
 * the other steps in the JPEG decompression process.
 *
 * @param handle a handle to a TurboJPEG decompressor or transformer instance
 *
 * @param srcPlanes an array of pointers to Y, U (Cb), and V (Cr) image planes
 * (or just a Y plane, if decoding a grayscale image) that contain a YUV image
 * to be decoded.  These planes can be contiguous or non-contiguous in memory.
 * The size of each plane should match the value returned by #tjPlaneSizeYUV()
 * for the given image width, height, strides, and level of chrominance
 * subsampling.  Refer to @ref YUVnotes "YUV Image Format Notes" for more
 * details.
 *
 * @param strides an array of integers, each specifying the number of bytes per
 * row in the corresponding plane of the YUV source image.  Setting the stride
 * for any plane to 0 is the same as setting it to the plane width (see
 * @ref YUVnotes "YUV Image Format Notes".)  If `strides` is NULL, then the
 * strides for all planes will be set to their respective plane widths.  You
 * can adjust the strides in order to specify an arbitrary amount of row
 * padding in each plane or to decode a subregion of a larger planar YUV image.
 *
 * @param subsamp the level of chrominance subsampling used in the YUV source
 * image (see @ref TJSAMP "Chrominance subsampling options".)
 *
 * @param dstBuf pointer to a buffer that will receive the packed-pixel decoded
 * image.  This buffer should normally be `pitch * height` bytes in size, but
 * the `dstBuf` pointer can also be used to decode into a specific region of a
 * larger buffer.
 *
 * @param width width (in pixels) of the source and destination images
 *
 * @param pitch bytes per row in the destination image.  Normally this should
 * be set to <tt>width * #tjPixelSize[pixelFormat]</tt>, if the destination
 * image should be unpadded, or
 * <tt>#TJPAD(width * #tjPixelSize[pixelFormat])</tt> if each row of the
 * destination image should be padded to the nearest multiple of 4 bytes, as is
 * the case for Windows bitmaps.  You can also be clever and use the pitch
 * parameter to skip rows, etc.  Setting this parameter to 0 is the equivalent
 * of setting it to <tt>width * #tjPixelSize[pixelFormat]</tt>.
 *
 * @param height height (in pixels) of the source and destination images
 *
 * @param pixelFormat pixel format of the destination image (see @ref TJPF
 * "Pixel formats".)
 *
 * @param flags the bitwise OR of one or more of the @ref TJFLAG_ACCURATEDCT
 * "flags"
 *
 * @return 0 if successful, or -1 if an error occurred (see #tjGetErrorStr2()
 * and #tjGetErrorCode().)
 */
DLLEXPORT int tjDecodeYUVPlanes(tjhandle handle,
                                const unsigned char **srcPlanes,
                                const int *strides, int subsamp,
                                unsigned char *dstBuf, int width, int pitch,
                                int height, int pixelFormat, int flags);


/**
 * Create a new TurboJPEG transformer instance.
 *
 * @return a handle to the newly-created instance, or NULL if an error
 * occurred (see #tjGetErrorStr2().)
 */
DLLEXPORT tjhandle tjInitTransform(void);


/**
 * Losslessly transform a JPEG image into another JPEG image.  Lossless
 * transforms work by moving the raw DCT coefficients from one JPEG image
 * structure to another without altering the values of the coefficients.  While
 * this is typically faster than decompressing the image, transforming it, and
 * re-compressing it, lossless transforms are not free.  Each lossless
 * transform requires reading and performing Huffman decoding on all of the
 * coefficients in the source image, regardless of the size of the destination
 * image.  Thus, this function provides a means of generating multiple
 * transformed images from the same source or applying multiple transformations
 * simultaneously, in order to eliminate the need to read the source
 * coefficients multiple times.
 *
 * @param handle a handle to a TurboJPEG transformer instance
 *
 * @param jpegBuf pointer to a byte buffer containing the JPEG source image to
 * transform
 *
 * @param jpegSize size of the JPEG source image (in bytes)
 *
 * @param n the number of transformed JPEG images to generate
 *
 * @param dstBufs pointer to an array of n byte buffers.  `dstBufs[i]` will
 * receive a JPEG image that has been transformed using the parameters in
 * `transforms[i]`.  TurboJPEG has the ability to reallocate the JPEG
 * destination buffer to accommodate the size of the transformed JPEG image.
 * Thus, you can choose to:
 * -# pre-allocate the JPEG destination buffer with an arbitrary size using
 * #tjAlloc() and let TurboJPEG grow the buffer as needed,
 * -# set `dstBufs[i]` to NULL to tell TurboJPEG to allocate the buffer for
 * you, or
 * -# pre-allocate the buffer to a "worst case" size determined by calling
 * #tjBufSize() with the transformed or cropped width and height and the level
 * of subsampling used in the source image.  Under normal circumstances, this
 * should ensure that the buffer never has to be re-allocated.  (Setting
 * #TJFLAG_NOREALLOC guarantees that it won't be.)  Note, however, that there
 * are some rare cases (such as transforming images with a large amount of
 * embedded EXIF or ICC profile data) in which the transformed JPEG image will
 * be larger than the worst-case size, and #TJFLAG_NOREALLOC cannot be used in
 * those cases.
 * .
 * If you choose option 1, then `dstSizes[i]` should be set to the size of your
 * pre-allocated buffer.  In any case, unless you have set #TJFLAG_NOREALLOC,
 * you should always check `dstBufs[i]` upon return from this function, as it
 * may have changed.
 *
 * @param dstSizes pointer to an array of n unsigned long variables that will
 * receive the actual sizes (in bytes) of each transformed JPEG image.  If
 * `dstBufs[i]` points to a pre-allocated buffer, then `dstSizes[i]` should be
 * set to the size of the buffer.  Upon return, `dstSizes[i]` will contain the
 * size of the transformed JPEG image (in bytes.)
 *
 * @param transforms pointer to an array of n #tjtransform structures, each of
 * which specifies the transform parameters and/or cropping region for the
 * corresponding transformed JPEG image.
 *
 * @param flags the bitwise OR of one or more of the @ref TJFLAG_ACCURATEDCT
 * "flags"
 *
 * @return 0 if successful, or -1 if an error occurred (see #tjGetErrorStr2()
 * and #tjGetErrorCode().)
 */
DLLEXPORT int tjTransform(tjhandle handle, const unsigned char *jpegBuf,
                          unsigned long jpegSize, int n,
                          unsigned char **dstBufs, unsigned long *dstSizes,
                          tjtransform *transforms, int flags);


/**
 * Destroy a TurboJPEG compressor, decompressor, or transformer instance.
 *
 * @param handle a handle to a TurboJPEG compressor, decompressor or
 * transformer instance
 *
 * @return 0 if successful, or -1 if an error occurred (see #tjGetErrorStr2().)
 */
DLLEXPORT int tjDestroy(tjhandle handle);


/**
 * Allocate a byte buffer for use with TurboJPEG.  You should always use this
 * function to allocate the JPEG destination buffer(s) for the compression and
 * transform functions unless you are disabling automatic buffer (re)allocation
 * (by setting #TJFLAG_NOREALLOC.)
 *
 * @param bytes the number of bytes to allocate
 *
 * @return a pointer to a newly-allocated buffer with the specified number of
 * bytes.
 *
 * @sa tjFree()
 */
DLLEXPORT unsigned char *tjAlloc(int bytes);


/**
 * Load a packed-pixel image from disk into memory.
 *
 * @param filename name of a file containing a packed-pixel image in Windows
 * BMP or PBMPLUS (PPM/PGM) format
 *
 * @param width pointer to an integer variable that will receive the width (in
 * pixels) of the packed-pixel image
 *
 * @param align row alignment of the packed-pixel buffer to be returned (must
 * be a power of 2.)  Setting this parameter to n will cause all rows in the
 * buffer to be padded to the nearest multiple of n bytes (1 = unpadded.)
 *
 * @param height pointer to an integer variable that will receive the height
 * (in pixels) of the packed-pixel image
 *
 * @param pixelFormat pointer to an integer variable that specifies or will
 * receive the pixel format of the packed-pixel buffer.  The behavior of
 * #tjLoadImage() will vary depending on the value of `*pixelFormat` passed to
 * the function:
 * - @ref TJPF_UNKNOWN : The packed-pixel buffer returned by this function will
 * use the most optimal pixel format for the file type, and `*pixelFormat` will
 * contain the ID of that pixel format upon successful return from this
 * function.
 * - @ref TJPF_GRAY : Only PGM files and 8-bit-per-pixel BMP files with a
 * grayscale colormap can be loaded.
 * - @ref TJPF_CMYK : The RGB or grayscale pixels stored in the file will be
 * converted using a quick & dirty algorithm that is suitable only for testing
 * purposes.  (Proper conversion between CMYK and other formats requires a
 * color management system.)
 * - Other @ref TJPF "pixel formats" : The packed-pixel buffer will use the
 * specified pixel format, and pixel format conversion will be performed if
 * necessary.
 *
 * @param flags the bitwise OR of one or more of the @ref TJFLAG_BOTTOMUP
 * "flags".
 *
 * @return a pointer to a newly-allocated buffer containing the packed-pixel
 * image, converted to the chosen pixel format and with the chosen row
 * alignment, or NULL if an error occurred (see #tjGetErrorStr2().)  This
 * buffer should be freed using #tjFree().
 */
DLLEXPORT unsigned char *tjLoadImage(const char *filename, int *width,
                                     int align, int *height, int *pixelFormat,
                                     int flags);


/**
 * Save a packed-pixel image from memory to disk.
 *
 * @param filename name of a file to which to save the packed-pixel image.  The
 * image will be stored in Windows BMP or PBMPLUS (PPM/PGM) format, depending
 * on the file extension.
 *
 * @param buffer pointer to a buffer containing a packed-pixel RGB, grayscale,
 * or CMYK image to be saved
 *
 * @param width width (in pixels) of the packed-pixel image
 *
 * @param pitch bytes per row in the packed-pixel image.  Setting this
 * parameter to 0 is the equivalent of setting it to
 * <tt>width * #tjPixelSize[pixelFormat]</tt>.
 *
 * @param height height (in pixels) of the packed-pixel image
 *
 * @param pixelFormat pixel format of the packed-pixel image (see @ref TJPF
 * "Pixel formats".)  If this parameter is set to @ref TJPF_GRAY, then the
 * image will be stored in PGM or 8-bit-per-pixel (indexed color) BMP format.
 * Otherwise, the image will be stored in PPM or 24-bit-per-pixel BMP format.
 * If this parameter is set to @ref TJPF_CMYK, then the CMYK pixels will be
 * converted to RGB using a quick & dirty algorithm that is suitable only for
 * testing purposes.  (Proper conversion between CMYK and other formats
 * requires a color management system.)
 *
 * @param flags the bitwise OR of one or more of the @ref TJFLAG_BOTTOMUP
 * "flags".
 *
 * @return 0 if successful, or -1 if an error occurred (see #tjGetErrorStr2().)
 */
DLLEXPORT int tjSaveImage(const char *filename, unsigned char *buffer,
                          int width, int pitch, int height, int pixelFormat,
                          int flags);


/**
 * Free a byte buffer previously allocated by TurboJPEG.  You should always use
 * this function to free JPEG destination buffer(s) that were automatically
 * (re)allocated by the compression and transform functions or that were
 * manually allocated using #tjAlloc().
 *
 * @param buffer address of the buffer to free.  If the address is NULL, then
 * this function has no effect.
 *
 * @sa tjAlloc()
 */
DLLEXPORT void tjFree(unsigned char *buffer);


/**
 * Returns a descriptive error message explaining why the last command failed.
 *
 * @param handle a handle to a TurboJPEG compressor, decompressor, or
 * transformer instance, or NULL if the error was generated by a global
 * function (but note that retrieving the error message for a global function
 * is thread-safe only on platforms that support thread-local storage.)
 *
 * @return a descriptive error message explaining why the last command failed.
 */
DLLEXPORT char *tjGetErrorStr2(tjhandle handle);


/**
 * Returns a code indicating the severity of the last error.  See
 * @ref TJERR "Error codes".
 *
 * @param handle a handle to a TurboJPEG compressor, decompressor or
 * transformer instance
 *
 * @return a code indicating the severity of the last error.  See
 * @ref TJERR "Error codes".
 */
DLLEXPORT int tjGetErrorCode(tjhandle handle);


/* Backward compatibility functions and macros (nothing to see here) */

/* TurboJPEG 1.0+ */

#define NUMSUBOPT  TJ_NUMSAMP
#define TJ_444  TJSAMP_444
#define TJ_422  TJSAMP_422
#define TJ_420  TJSAMP_420
#define TJ_411  TJSAMP_420
#define TJ_GRAYSCALE  TJSAMP_GRAY

#define TJ_BGR  1
#define TJ_BOTTOMUP  TJFLAG_BOTTOMUP
#define TJ_FORCEMMX  TJFLAG_FORCEMMX
#define TJ_FORCESSE  TJFLAG_FORCESSE
#define TJ_FORCESSE2  TJFLAG_FORCESSE2
#define TJ_ALPHAFIRST  64
#define TJ_FORCESSE3  TJFLAG_FORCESSE3
#define TJ_FASTUPSAMPLE  TJFLAG_FASTUPSAMPLE

DLLEXPORT unsigned long TJBUFSIZE(int width, int height);

DLLEXPORT int tjCompress(tjhandle handle, unsigned char *srcBuf, int width,
                         int pitch, int height, int pixelSize,
                         unsigned char *dstBuf, unsigned long *compressedSize,
                         int jpegSubsamp, int jpegQual, int flags);

DLLEXPORT int tjDecompress(tjhandle handle, unsigned char *jpegBuf,
                           unsigned long jpegSize, unsigned char *dstBuf,
                           int width, int pitch, int height, int pixelSize,
                           int flags);

DLLEXPORT int tjDecompressHeader(tjhandle handle, unsigned char *jpegBuf,
                                 unsigned long jpegSize, int *width,
                                 int *height);

DLLEXPORT char *tjGetErrorStr(void);

/* TurboJPEG 1.1+ */

#define TJ_YUV  512

DLLEXPORT unsigned long TJBUFSIZEYUV(int width, int height, int jpegSubsamp);

DLLEXPORT int tjDecompressHeader2(tjhandle handle, unsigned char *jpegBuf,
                                  unsigned long jpegSize, int *width,
                                  int *height, int *jpegSubsamp);

DLLEXPORT int tjDecompressToYUV(tjhandle handle, unsigned char *jpegBuf,
                                unsigned long jpegSize, unsigned char *dstBuf,
                                int flags);

DLLEXPORT int tjEncodeYUV(tjhandle handle, unsigned char *srcBuf, int width,
                          int pitch, int height, int pixelSize,
                          unsigned char *dstBuf, int subsamp, int flags);

/* TurboJPEG 1.2+ */

#define TJFLAG_FORCEMMX  8
#define TJFLAG_FORCESSE  16
#define TJFLAG_FORCESSE2  32
#define TJFLAG_FORCESSE3  128

DLLEXPORT unsigned long tjBufSizeYUV(int width, int height, int subsamp);

DLLEXPORT int tjEncodeYUV2(tjhandle handle, unsigned char *srcBuf, int width,
                           int pitch, int height, int pixelFormat,
                           unsigned char *dstBuf, int subsamp, int flags);

/**
 * @}
 */

#ifdef __cplusplus
}
#endif

#endif