jdsample.c - third_party/libjpeg-turbo - Git at Google

 /*
  * jdsample.c
  *
  * Copyright (C) 1991-1996, Thomas G. Lane.
  * Modified 2002-2008 by Guido Vollbeding.
  * This file is part of the Independent JPEG Group's software.
  * For conditions of distribution and use, see the accompanying README file.
  *
  * This file contains upsampling routines.
  *
  * Upsampling input data is counted in "row groups".  A row group
  * is defined to be (v_samp_factor * DCT_v_scaled_size / min_DCT_v_scaled_size)
  * sample rows of each component.  Upsampling will normally produce
  * max_v_samp_factor pixel rows from each row group (but this could vary
  * if the upsampler is applying a scale factor of its own).
  *
  * An excellent reference for image resampling is
  *   Digital Image Warping, George Wolberg, 1990.
  *   Pub. by IEEE Computer Society Press, Los Alamitos, CA. ISBN 0-8186-8944-7.
  */

 #define JPEG_INTERNALS
 #include "jinclude.h"
 #include "jpeglib.h"


 /* Pointer to routine to upsample a single component */
 typedef JMETHOD(void, upsample1_ptr,
 		(j_decompress_ptr cinfo, jpeg_component_info * compptr,
 		 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr));

 /* Private subobject */

 typedef struct {
   struct jpeg_upsampler pub;	/* public fields */

   /* Color conversion buffer.  When using separate upsampling and color
    * conversion steps, this buffer holds one upsampled row group until it
    * has been color converted and output.
    * Note: we do not allocate any storage for component(s) which are full-size,
    * ie do not need rescaling.  The corresponding entry of color_buf[] is
    * simply set to point to the input data array, thereby avoiding copying.
    */
   JSAMPARRAY color_buf[MAX_COMPONENTS];

   /* Per-component upsampling method pointers */
   upsample1_ptr methods[MAX_COMPONENTS];

   int next_row_out;		/* counts rows emitted from color_buf */
   JDIMENSION rows_to_go;	/* counts rows remaining in image */

   /* Height of an input row group for each component. */
   int rowgroup_height[MAX_COMPONENTS];

   /* These arrays save pixel expansion factors so that int_expand need not
    * recompute them each time.  They are unused for other upsampling methods.
    */
   UINT8 h_expand[MAX_COMPONENTS];
   UINT8 v_expand[MAX_COMPONENTS];
 } my_upsampler;

 typedef my_upsampler * my_upsample_ptr;


 /*
  * Initialize for an upsampling pass.
  */

 METHODDEF(void)
 start_pass_upsample (j_decompress_ptr cinfo)
 {
   my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;

   /* Mark the conversion buffer empty */
   upsample->next_row_out = cinfo->max_v_samp_factor;
   /* Initialize total-height counter for detecting bottom of image */
   upsample->rows_to_go = cinfo->output_height;
 }


 /*
  * Control routine to do upsampling (and color conversion).
  *
  * In this version we upsample each component independently.
  * We upsample one row group into the conversion buffer, then apply
  * color conversion a row at a time.
  */

 METHODDEF(void)
 sep_upsample (j_decompress_ptr cinfo,
 	      JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
 	      JDIMENSION in_row_groups_avail,
 	      JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
 	      JDIMENSION out_rows_avail)
 {
   my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
   int ci;
   jpeg_component_info * compptr;
   JDIMENSION num_rows;

   /* Fill the conversion buffer, if it's empty */
   if (upsample->next_row_out >= cinfo->max_v_samp_factor) {
     for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
 	 ci++, compptr++) {
       /* Invoke per-component upsample method.  Notice we pass a POINTER
        * to color_buf[ci], so that fullsize_upsample can change it.
        */
       (*upsample->methods[ci]) (cinfo, compptr,
 	input_buf[ci] + (*in_row_group_ctr * upsample->rowgroup_height[ci]),
 	upsample->color_buf + ci);
     }
     upsample->next_row_out = 0;
   }

   /* Color-convert and emit rows */

   /* How many we have in the buffer: */
   num_rows = (JDIMENSION) (cinfo->max_v_samp_factor - upsample->next_row_out);
   /* Not more than the distance to the end of the image.  Need this test
    * in case the image height is not a multiple of max_v_samp_factor:
    */
   if (num_rows > upsample->rows_to_go)
     num_rows = upsample->rows_to_go;
   /* And not more than what the client can accept: */
   out_rows_avail -= *out_row_ctr;
   if (num_rows > out_rows_avail)
     num_rows = out_rows_avail;

   (*cinfo->cconvert->color_convert) (cinfo, upsample->color_buf,
 				     (JDIMENSION) upsample->next_row_out,
 				     output_buf + *out_row_ctr,
 				     (int) num_rows);

   /* Adjust counts */
   *out_row_ctr += num_rows;
   upsample->rows_to_go -= num_rows;
   upsample->next_row_out += num_rows;
   /* When the buffer is emptied, declare this input row group consumed */
   if (upsample->next_row_out >= cinfo->max_v_samp_factor)
     (*in_row_group_ctr)++;
 }


 /*
  * These are the routines invoked by sep_upsample to upsample pixel values
  * of a single component.  One row group is processed per call.
  */


 /*
  * For full-size components, we just make color_buf[ci] point at the
  * input buffer, and thus avoid copying any data.  Note that this is
  * safe only because sep_upsample doesn't declare the input row group
  * "consumed" until we are done color converting and emitting it.
  */

 METHODDEF(void)
 fullsize_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
 		   JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
 {
   *output_data_ptr = input_data;
 }


 /*
  * This is a no-op version used for "uninteresting" components.
  * These components will not be referenced by color conversion.
  */

 METHODDEF(void)
 noop_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
 	       JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
 {
   *output_data_ptr = NULL;	/* safety check */
 }


 /*
  * This version handles any integral sampling ratios.
  * This is not used for typical JPEG files, so it need not be fast.
  * Nor, for that matter, is it particularly accurate: the algorithm is
  * simple replication of the input pixel onto the corresponding output
  * pixels.  The hi-falutin sampling literature refers to this as a
  * "box filter".  A box filter tends to introduce visible artifacts,
  * so if you are actually going to use 3:1 or 4:1 sampling ratios
  * you would be well advised to improve this code.
  */

 METHODDEF(void)
 int_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
 	      JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
 {
   my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
   JSAMPARRAY output_data = *output_data_ptr;
   register JSAMPROW inptr, outptr;
   register JSAMPLE invalue;
   register int h;
   JSAMPROW outend;
   int h_expand, v_expand;
   int inrow, outrow;

   h_expand = upsample->h_expand[compptr->component_index];
   v_expand = upsample->v_expand[compptr->component_index];

   inrow = outrow = 0;
   while (outrow < cinfo->max_v_samp_factor) {
     /* Generate one output row with proper horizontal expansion */
     inptr = input_data[inrow];
     outptr = output_data[outrow];
     outend = outptr + cinfo->output_width;
     while (outptr < outend) {
       invalue = *inptr++;	/* don't need GETJSAMPLE() here */
       for (h = h_expand; h > 0; h--) {
 	*outptr++ = invalue;
       }
     }
     /* Generate any additional output rows by duplicating the first one */
     if (v_expand > 1) {
       jcopy_sample_rows(output_data, outrow, output_data, outrow+1,
 			v_expand-1, cinfo->output_width);
     }
     inrow++;
     outrow += v_expand;
   }
 }


 /*
  * Fast processing for the common case of 2:1 horizontal and 1:1 vertical.
  * It's still a box filter.
  */

 METHODDEF(void)
 h2v1_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
 	       JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
 {
   JSAMPARRAY output_data = *output_data_ptr;
   register JSAMPROW inptr, outptr;
   register JSAMPLE invalue;
   JSAMPROW outend;
   int outrow;

   for (outrow = 0; outrow < cinfo->max_v_samp_factor; outrow++) {
     inptr = input_data[outrow];
     outptr = output_data[outrow];
     outend = outptr + cinfo->output_width;
     while (outptr < outend) {
       invalue = *inptr++;	/* don't need GETJSAMPLE() here */
       *outptr++ = invalue;
       *outptr++ = invalue;
     }
   }
 }


 /*
  * Fast processing for the common case of 2:1 horizontal and 2:1 vertical.
  * It's still a box filter.
  */

 METHODDEF(void)
 h2v2_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
 	       JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
 {
   JSAMPARRAY output_data = *output_data_ptr;
   register JSAMPROW inptr, outptr;
   register JSAMPLE invalue;
   JSAMPROW outend;
   int inrow, outrow;

   inrow = outrow = 0;
   while (outrow < cinfo->max_v_samp_factor) {
     inptr = input_data[inrow];
     outptr = output_data[outrow];
     outend = outptr + cinfo->output_width;
     while (outptr < outend) {
       invalue = *inptr++;	/* don't need GETJSAMPLE() here */
       *outptr++ = invalue;
       *outptr++ = invalue;
     }
     jcopy_sample_rows(output_data, outrow, output_data, outrow+1,
 		      1, cinfo->output_width);
     inrow++;
     outrow += 2;
   }
 }


 /*
  * Module initialization routine for upsampling.
  */

 GLOBAL(void)
 jinit_upsampler (j_decompress_ptr cinfo)
 {
   my_upsample_ptr upsample;
   int ci;
   jpeg_component_info * compptr;
   boolean need_buffer;
   int h_in_group, v_in_group, h_out_group, v_out_group;

   upsample = (my_upsample_ptr)
     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 				SIZEOF(my_upsampler));
   cinfo->upsample = (struct jpeg_upsampler *) upsample;
   upsample->pub.start_pass = start_pass_upsample;
   upsample->pub.upsample = sep_upsample;
   upsample->pub.need_context_rows = FALSE; /* until we find out differently */

   if (cinfo->CCIR601_sampling)	/* this isn't supported */
     ERREXIT(cinfo, JERR_CCIR601_NOTIMPL);

   /* Verify we can handle the sampling factors, select per-component methods,
    * and create storage as needed.
    */
   for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
        ci++, compptr++) {
     /* Compute size of an "input group" after IDCT scaling.  This many samples
      * are to be converted to max_h_samp_factor * max_v_samp_factor pixels.
      */
     h_in_group = (compptr->h_samp_factor * compptr->DCT_h_scaled_size) /
 		 cinfo->min_DCT_h_scaled_size;
     v_in_group = (compptr->v_samp_factor * compptr->DCT_v_scaled_size) /
 		 cinfo->min_DCT_v_scaled_size;
     h_out_group = cinfo->max_h_samp_factor;
     v_out_group = cinfo->max_v_samp_factor;
     upsample->rowgroup_height[ci] = v_in_group; /* save for use later */
     need_buffer = TRUE;
     if (! compptr->component_needed) {
       /* Don't bother to upsample an uninteresting component. */
       upsample->methods[ci] = noop_upsample;
       need_buffer = FALSE;
     } else if (h_in_group == h_out_group && v_in_group == v_out_group) {
       /* Fullsize components can be processed without any work. */
       upsample->methods[ci] = fullsize_upsample;
       need_buffer = FALSE;
     } else if (h_in_group * 2 == h_out_group &&
 	       v_in_group == v_out_group) {
       /* Special case for 2h1v upsampling */
       upsample->methods[ci] = h2v1_upsample;
     } else if (h_in_group * 2 == h_out_group &&
 	       v_in_group * 2 == v_out_group) {
       /* Special case for 2h2v upsampling */
       upsample->methods[ci] = h2v2_upsample;
     } else if ((h_out_group % h_in_group) == 0 &&
 	       (v_out_group % v_in_group) == 0) {
       /* Generic integral-factors upsampling method */
       upsample->methods[ci] = int_upsample;
       upsample->h_expand[ci] = (UINT8) (h_out_group / h_in_group);
       upsample->v_expand[ci] = (UINT8) (v_out_group / v_in_group);
     } else
       ERREXIT(cinfo, JERR_FRACT_SAMPLE_NOTIMPL);
     if (need_buffer) {
       upsample->color_buf[ci] = (*cinfo->mem->alloc_sarray)
 	((j_common_ptr) cinfo, JPOOL_IMAGE,
 	 (JDIMENSION) jround_up((long) cinfo->output_width,
 				(long) cinfo->max_h_samp_factor),
 	 (JDIMENSION) cinfo->max_v_samp_factor);
     }
   }
 }
	/*
	* jdsample.c
	*
	* Copyright (C) 1991-1996, Thomas G. Lane.
	* Modified 2002-2008 by Guido Vollbeding.
	* This file is part of the Independent JPEG Group's software.
	* For conditions of distribution and use, see the accompanying README file.
	*
	* This file contains upsampling routines.
	*
	* Upsampling input data is counted in "row groups". A row group
	* is defined to be (v_samp_factor * DCT_v_scaled_size / min_DCT_v_scaled_size)
	* sample rows of each component. Upsampling will normally produce
	* max_v_samp_factor pixel rows from each row group (but this could vary
	* if the upsampler is applying a scale factor of its own).
	*
	* An excellent reference for image resampling is
	* Digital Image Warping, George Wolberg, 1990.
	* Pub. by IEEE Computer Society Press, Los Alamitos, CA. ISBN 0-8186-8944-7.
	*/

	#define JPEG_INTERNALS
	#include "jinclude.h"
	#include "jpeglib.h"


	/* Pointer to routine to upsample a single component */
	typedef JMETHOD(void, upsample1_ptr,
	(j_decompress_ptr cinfo, jpeg_component_info * compptr,
	JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr));

	/* Private subobject */

	typedef struct {
	struct jpeg_upsampler pub; /* public fields */

	/* Color conversion buffer. When using separate upsampling and color
	* conversion steps, this buffer holds one upsampled row group until it
	* has been color converted and output.
	* Note: we do not allocate any storage for component(s) which are full-size,
	* ie do not need rescaling. The corresponding entry of color_buf[] is
	* simply set to point to the input data array, thereby avoiding copying.
	*/
	JSAMPARRAY color_buf[MAX_COMPONENTS];

	/* Per-component upsampling method pointers */
	upsample1_ptr methods[MAX_COMPONENTS];

	int next_row_out; /* counts rows emitted from color_buf */
	JDIMENSION rows_to_go; /* counts rows remaining in image */

	/* Height of an input row group for each component. */
	int rowgroup_height[MAX_COMPONENTS];

	/* These arrays save pixel expansion factors so that int_expand need not
	* recompute them each time. They are unused for other upsampling methods.
	*/
	UINT8 h_expand[MAX_COMPONENTS];
	UINT8 v_expand[MAX_COMPONENTS];
	} my_upsampler;

	typedef my_upsampler * my_upsample_ptr;


	/*
	* Initialize for an upsampling pass.
	*/

	METHODDEF(void)
	start_pass_upsample (j_decompress_ptr cinfo)
	{
	my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;

	/* Mark the conversion buffer empty */
	upsample->next_row_out = cinfo->max_v_samp_factor;
	/* Initialize total-height counter for detecting bottom of image */
	upsample->rows_to_go = cinfo->output_height;
	}


	/*
	* Control routine to do upsampling (and color conversion).
	*
	* In this version we upsample each component independently.
	* We upsample one row group into the conversion buffer, then apply
	* color conversion a row at a time.
	*/

	METHODDEF(void)
	sep_upsample (j_decompress_ptr cinfo,
	JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
	JDIMENSION in_row_groups_avail,
	JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
	JDIMENSION out_rows_avail)
	{
	my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
	int ci;
	jpeg_component_info * compptr;
	JDIMENSION num_rows;

	/* Fill the conversion buffer, if it's empty */
	if (upsample->next_row_out >= cinfo->max_v_samp_factor) {
	for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
	ci++, compptr++) {
	/* Invoke per-component upsample method. Notice we pass a POINTER
	* to color_buf[ci], so that fullsize_upsample can change it.
	*/
	(*upsample->methods[ci]) (cinfo, compptr,
	input_buf[ci] + (in_row_group_ctr upsample->rowgroup_height[ci]),
	upsample->color_buf + ci);
	}
	upsample->next_row_out = 0;
	}

	/* Color-convert and emit rows */

	/* How many we have in the buffer: */
	num_rows = (JDIMENSION) (cinfo->max_v_samp_factor - upsample->next_row_out);
	/* Not more than the distance to the end of the image. Need this test
	* in case the image height is not a multiple of max_v_samp_factor:
	*/
	if (num_rows > upsample->rows_to_go)
	num_rows = upsample->rows_to_go;
	/* And not more than what the client can accept: */
	out_rows_avail -= *out_row_ctr;
	if (num_rows > out_rows_avail)
	num_rows = out_rows_avail;

	(*cinfo->cconvert->color_convert) (cinfo, upsample->color_buf,
	(JDIMENSION) upsample->next_row_out,
	output_buf + *out_row_ctr,
	(int) num_rows);

	/* Adjust counts */
	*out_row_ctr += num_rows;
	upsample->rows_to_go -= num_rows;
	upsample->next_row_out += num_rows;
	/* When the buffer is emptied, declare this input row group consumed */
	if (upsample->next_row_out >= cinfo->max_v_samp_factor)
	(*in_row_group_ctr)++;
	}


	/*
	* These are the routines invoked by sep_upsample to upsample pixel values
	* of a single component. One row group is processed per call.
	*/


	/*
	* For full-size components, we just make color_buf[ci] point at the
	* input buffer, and thus avoid copying any data. Note that this is
	* safe only because sep_upsample doesn't declare the input row group
	* "consumed" until we are done color converting and emitting it.
	*/

	METHODDEF(void)
	fullsize_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
	JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
	{
	*output_data_ptr = input_data;
	}


	/*
	* This is a no-op version used for "uninteresting" components.
	* These components will not be referenced by color conversion.
	*/

	METHODDEF(void)
	noop_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
	JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
	{
	output_data_ptr = NULL; / safety check */
	}


	/*
	* This version handles any integral sampling ratios.
	* This is not used for typical JPEG files, so it need not be fast.
	* Nor, for that matter, is it particularly accurate: the algorithm is
	* simple replication of the input pixel onto the corresponding output
	* pixels. The hi-falutin sampling literature refers to this as a
	* "box filter". A box filter tends to introduce visible artifacts,
	* so if you are actually going to use 3:1 or 4:1 sampling ratios
	* you would be well advised to improve this code.
	*/

	METHODDEF(void)
	int_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
	JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
	{
	my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
	JSAMPARRAY output_data = *output_data_ptr;
	register JSAMPROW inptr, outptr;
	register JSAMPLE invalue;
	register int h;
	JSAMPROW outend;
	int h_expand, v_expand;
	int inrow, outrow;

	h_expand = upsample->h_expand[compptr->component_index];
	v_expand = upsample->v_expand[compptr->component_index];

	inrow = outrow = 0;
	while (outrow < cinfo->max_v_samp_factor) {
	/* Generate one output row with proper horizontal expansion */
	inptr = input_data[inrow];
	outptr = output_data[outrow];
	outend = outptr + cinfo->output_width;
	while (outptr < outend) {
	invalue = inptr++; / don't need GETJSAMPLE() here */
	for (h = h_expand; h > 0; h--) {
	*outptr++ = invalue;
	}
	}
	/* Generate any additional output rows by duplicating the first one */
	if (v_expand > 1) {
	jcopy_sample_rows(output_data, outrow, output_data, outrow+1,
	v_expand-1, cinfo->output_width);
	}
	inrow++;
	outrow += v_expand;
	}
	}


	/*
	* Fast processing for the common case of 2:1 horizontal and 1:1 vertical.
	* It's still a box filter.
	*/

	METHODDEF(void)
	h2v1_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
	JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
	{
	JSAMPARRAY output_data = *output_data_ptr;
	register JSAMPROW inptr, outptr;
	register JSAMPLE invalue;
	JSAMPROW outend;
	int outrow;

	for (outrow = 0; outrow < cinfo->max_v_samp_factor; outrow++) {
	inptr = input_data[outrow];
	outptr = output_data[outrow];
	outend = outptr + cinfo->output_width;
	while (outptr < outend) {
	invalue = inptr++; / don't need GETJSAMPLE() here */
	*outptr++ = invalue;
	*outptr++ = invalue;
	}
	}
	}


	/*
	* Fast processing for the common case of 2:1 horizontal and 2:1 vertical.
	* It's still a box filter.
	*/

	METHODDEF(void)
	h2v2_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
	JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
	{
	JSAMPARRAY output_data = *output_data_ptr;
	register JSAMPROW inptr, outptr;
	register JSAMPLE invalue;
	JSAMPROW outend;
	int inrow, outrow;

	inrow = outrow = 0;
	while (outrow < cinfo->max_v_samp_factor) {
	inptr = input_data[inrow];
	outptr = output_data[outrow];
	outend = outptr + cinfo->output_width;
	while (outptr < outend) {
	invalue = inptr++; / don't need GETJSAMPLE() here */
	*outptr++ = invalue;
	*outptr++ = invalue;
	}
	jcopy_sample_rows(output_data, outrow, output_data, outrow+1,
	1, cinfo->output_width);
	inrow++;
	outrow += 2;
	}
	}


	/*
	* Module initialization routine for upsampling.
	*/

	GLOBAL(void)
	jinit_upsampler (j_decompress_ptr cinfo)
	{
	my_upsample_ptr upsample;
	int ci;
	jpeg_component_info * compptr;
	boolean need_buffer;
	int h_in_group, v_in_group, h_out_group, v_out_group;

	upsample = (my_upsample_ptr)
	(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
	SIZEOF(my_upsampler));
	cinfo->upsample = (struct jpeg_upsampler *) upsample;
	upsample->pub.start_pass = start_pass_upsample;
	upsample->pub.upsample = sep_upsample;
	upsample->pub.need_context_rows = FALSE; /* until we find out differently */

	if (cinfo->CCIR601_sampling) /* this isn't supported */
	ERREXIT(cinfo, JERR_CCIR601_NOTIMPL);

	/* Verify we can handle the sampling factors, select per-component methods,
	* and create storage as needed.
	*/
	for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
	ci++, compptr++) {
	/* Compute size of an "input group" after IDCT scaling. This many samples
	* are to be converted to max_h_samp_factor * max_v_samp_factor pixels.
	*/
	h_in_group = (compptr->h_samp_factor * compptr->DCT_h_scaled_size) /
	cinfo->min_DCT_h_scaled_size;
	v_in_group = (compptr->v_samp_factor * compptr->DCT_v_scaled_size) /
	cinfo->min_DCT_v_scaled_size;
	h_out_group = cinfo->max_h_samp_factor;
	v_out_group = cinfo->max_v_samp_factor;
	upsample->rowgroup_height[ci] = v_in_group; /* save for use later */
	need_buffer = TRUE;
	if (! compptr->component_needed) {
	/* Don't bother to upsample an uninteresting component. */
	upsample->methods[ci] = noop_upsample;
	need_buffer = FALSE;
	} else if (h_in_group == h_out_group && v_in_group == v_out_group) {
	/* Fullsize components can be processed without any work. */
	upsample->methods[ci] = fullsize_upsample;
	need_buffer = FALSE;
	} else if (h_in_group * 2 == h_out_group &&
	v_in_group == v_out_group) {
	/* Special case for 2h1v upsampling */
	upsample->methods[ci] = h2v1_upsample;
	} else if (h_in_group * 2 == h_out_group &&
	v_in_group * 2 == v_out_group) {
	/* Special case for 2h2v upsampling */
	upsample->methods[ci] = h2v2_upsample;
	} else if ((h_out_group % h_in_group) == 0 &&
	(v_out_group % v_in_group) == 0) {
	/* Generic integral-factors upsampling method */
	upsample->methods[ci] = int_upsample;
	upsample->h_expand[ci] = (UINT8) (h_out_group / h_in_group);
	upsample->v_expand[ci] = (UINT8) (v_out_group / v_in_group);
	} else
	ERREXIT(cinfo, JERR_FRACT_SAMPLE_NOTIMPL);
	if (need_buffer) {
	upsample->color_buf[ci] = (*cinfo->mem->alloc_sarray)
	((j_common_ptr) cinfo, JPOOL_IMAGE,
	(JDIMENSION) jround_up((long) cinfo->output_width,
	(long) cinfo->max_h_samp_factor),
	(JDIMENSION) cinfo->max_v_samp_factor);
	}
	}
	}