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

 /*
  * jidctred.c
  *
  * This file was part of the Independent JPEG Group's software.
  * Copyright (C) 1994-1998, Thomas G. Lane.
  * libjpeg-turbo Modifications:
  * Copyright (C) 2015, D. R. Commander
  * For conditions of distribution and use, see the accompanying README.ijg
  * file.
  *
  * This file contains inverse-DCT routines that produce reduced-size output:
  * either 4x4, 2x2, or 1x1 pixels from an 8x8 DCT block.
  *
  * The implementation is based on the Loeffler, Ligtenberg and Moschytz (LL&M)
  * algorithm used in jidctint.c.  We simply replace each 8-to-8 1-D IDCT step
  * with an 8-to-4 step that produces the four averages of two adjacent outputs
  * (or an 8-to-2 step producing two averages of four outputs, for 2x2 output).
  * These steps were derived by computing the corresponding values at the end
  * of the normal LL&M code, then simplifying as much as possible.
  *
  * 1x1 is trivial: just take the DC coefficient divided by 8.
  *
  * See jidctint.c for additional comments.
  */

 #define JPEG_INTERNALS
 #include "jinclude.h"
 #include "jpeglib.h"
 #include "jdct.h"               /* Private declarations for DCT subsystem */

 #ifdef IDCT_SCALING_SUPPORTED


 /*
  * This module is specialized to the case DCTSIZE = 8.
  */

 #if DCTSIZE != 8
   Sorry, this code only copes with 8x8 DCTs. /* deliberate syntax err */
 #endif


 /* Scaling is the same as in jidctint.c. */

 #if BITS_IN_JSAMPLE == 8
 #define CONST_BITS  13
 #define PASS1_BITS  2
 #else
 #define CONST_BITS  13
 #define PASS1_BITS  1           /* lose a little precision to avoid overflow */
 #endif

 /* Some C compilers fail to reduce "FIX(constant)" at compile time, thus
  * causing a lot of useless floating-point operations at run time.
  * To get around this we use the following pre-calculated constants.
  * If you change CONST_BITS you may want to add appropriate values.
  * (With a reasonable C compiler, you can just rely on the FIX() macro...)
  */

 #if CONST_BITS == 13
 #define FIX_0_211164243  ((JLONG)  1730)        /* FIX(0.211164243) */
 #define FIX_0_509795579  ((JLONG)  4176)        /* FIX(0.509795579) */
 #define FIX_0_601344887  ((JLONG)  4926)        /* FIX(0.601344887) */
 #define FIX_0_720959822  ((JLONG)  5906)        /* FIX(0.720959822) */
 #define FIX_0_765366865  ((JLONG)  6270)        /* FIX(0.765366865) */
 #define FIX_0_850430095  ((JLONG)  6967)        /* FIX(0.850430095) */
 #define FIX_0_899976223  ((JLONG)  7373)        /* FIX(0.899976223) */
 #define FIX_1_061594337  ((JLONG)  8697)        /* FIX(1.061594337) */
 #define FIX_1_272758580  ((JLONG)  10426)       /* FIX(1.272758580) */
 #define FIX_1_451774981  ((JLONG)  11893)       /* FIX(1.451774981) */
 #define FIX_1_847759065  ((JLONG)  15137)       /* FIX(1.847759065) */
 #define FIX_2_172734803  ((JLONG)  17799)       /* FIX(2.172734803) */
 #define FIX_2_562915447  ((JLONG)  20995)       /* FIX(2.562915447) */
 #define FIX_3_624509785  ((JLONG)  29692)       /* FIX(3.624509785) */
 #else
 #define FIX_0_211164243  FIX(0.211164243)
 #define FIX_0_509795579  FIX(0.509795579)
 #define FIX_0_601344887  FIX(0.601344887)
 #define FIX_0_720959822  FIX(0.720959822)
 #define FIX_0_765366865  FIX(0.765366865)
 #define FIX_0_850430095  FIX(0.850430095)
 #define FIX_0_899976223  FIX(0.899976223)
 #define FIX_1_061594337  FIX(1.061594337)
 #define FIX_1_272758580  FIX(1.272758580)
 #define FIX_1_451774981  FIX(1.451774981)
 #define FIX_1_847759065  FIX(1.847759065)
 #define FIX_2_172734803  FIX(2.172734803)
 #define FIX_2_562915447  FIX(2.562915447)
 #define FIX_3_624509785  FIX(3.624509785)
 #endif


 /* Multiply a JLONG variable by a JLONG constant to yield a JLONG result.
  * For 8-bit samples with the recommended scaling, all the variable
  * and constant values involved are no more than 16 bits wide, so a
  * 16x16->32 bit multiply can be used instead of a full 32x32 multiply.
  * For 12-bit samples, a full 32-bit multiplication will be needed.
  */

 #if BITS_IN_JSAMPLE == 8
 #define MULTIPLY(var,const)  MULTIPLY16C16(var,const)
 #else
 #define MULTIPLY(var,const)  ((var) * (const))
 #endif


 /* Dequantize a coefficient by multiplying it by the multiplier-table
  * entry; produce an int result.  In this module, both inputs and result
  * are 16 bits or less, so either int or short multiply will work.
  */

 #define DEQUANTIZE(coef,quantval)  (((ISLOW_MULT_TYPE) (coef)) * (quantval))


 /*
  * Perform dequantization and inverse DCT on one block of coefficients,
  * producing a reduced-size 4x4 output block.
  */

 GLOBAL(void)
 jpeg_idct_4x4 (j_decompress_ptr cinfo, jpeg_component_info *compptr,
                JCOEFPTR coef_block,
                JSAMPARRAY output_buf, JDIMENSION output_col)
 {
   JLONG tmp0, tmp2, tmp10, tmp12;
   JLONG z1, z2, z3, z4;
   JCOEFPTR inptr;
   ISLOW_MULT_TYPE *quantptr;
   int *wsptr;
   JSAMPROW outptr;
   JSAMPLE *range_limit = IDCT_range_limit(cinfo);
   int ctr;
   int workspace[DCTSIZE*4];     /* buffers data between passes */
   SHIFT_TEMPS

   /* Pass 1: process columns from input, store into work array. */

   inptr = coef_block;
   quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
   wsptr = workspace;
   for (ctr = DCTSIZE; ctr > 0; inptr++, quantptr++, wsptr++, ctr--) {
     /* Don't bother to process column 4, because second pass won't use it */
     if (ctr == DCTSIZE-4)
       continue;
     if (inptr[DCTSIZE*1] == 0 && inptr[DCTSIZE*2] == 0 &&
         inptr[DCTSIZE*3] == 0 && inptr[DCTSIZE*5] == 0 &&
         inptr[DCTSIZE*6] == 0 && inptr[DCTSIZE*7] == 0) {
       /* AC terms all zero; we need not examine term 4 for 4x4 output */
       int dcval = LEFT_SHIFT(DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]),
                              PASS1_BITS);

       wsptr[DCTSIZE*0] = dcval;
       wsptr[DCTSIZE*1] = dcval;
       wsptr[DCTSIZE*2] = dcval;
       wsptr[DCTSIZE*3] = dcval;

       continue;
     }

     /* Even part */

     tmp0 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]);
     tmp0 = LEFT_SHIFT(tmp0, CONST_BITS+1);

     z2 = DEQUANTIZE(inptr[DCTSIZE*2], quantptr[DCTSIZE*2]);
     z3 = DEQUANTIZE(inptr[DCTSIZE*6], quantptr[DCTSIZE*6]);

     tmp2 = MULTIPLY(z2, FIX_1_847759065) + MULTIPLY(z3, - FIX_0_765366865);

     tmp10 = tmp0 + tmp2;
     tmp12 = tmp0 - tmp2;

     /* Odd part */

     z1 = DEQUANTIZE(inptr[DCTSIZE*7], quantptr[DCTSIZE*7]);
     z2 = DEQUANTIZE(inptr[DCTSIZE*5], quantptr[DCTSIZE*5]);
     z3 = DEQUANTIZE(inptr[DCTSIZE*3], quantptr[DCTSIZE*3]);
     z4 = DEQUANTIZE(inptr[DCTSIZE*1], quantptr[DCTSIZE*1]);

     tmp0 = MULTIPLY(z1, - FIX_0_211164243) /* sqrt(2) * (c3-c1) */
          + MULTIPLY(z2, FIX_1_451774981) /* sqrt(2) * (c3+c7) */
          + MULTIPLY(z3, - FIX_2_172734803) /* sqrt(2) * (-c1-c5) */
          + MULTIPLY(z4, FIX_1_061594337); /* sqrt(2) * (c5+c7) */

     tmp2 = MULTIPLY(z1, - FIX_0_509795579) /* sqrt(2) * (c7-c5) */
          + MULTIPLY(z2, - FIX_0_601344887) /* sqrt(2) * (c5-c1) */
          + MULTIPLY(z3, FIX_0_899976223) /* sqrt(2) * (c3-c7) */
          + MULTIPLY(z4, FIX_2_562915447); /* sqrt(2) * (c1+c3) */

     /* Final output stage */

     wsptr[DCTSIZE*0] = (int) DESCALE(tmp10 + tmp2, CONST_BITS-PASS1_BITS+1);
     wsptr[DCTSIZE*3] = (int) DESCALE(tmp10 - tmp2, CONST_BITS-PASS1_BITS+1);
     wsptr[DCTSIZE*1] = (int) DESCALE(tmp12 + tmp0, CONST_BITS-PASS1_BITS+1);
     wsptr[DCTSIZE*2] = (int) DESCALE(tmp12 - tmp0, CONST_BITS-PASS1_BITS+1);
   }

   /* Pass 2: process 4 rows from work array, store into output array. */

   wsptr = workspace;
   for (ctr = 0; ctr < 4; ctr++) {
     outptr = output_buf[ctr] + output_col;
     /* It's not clear whether a zero row test is worthwhile here ... */

 #ifndef NO_ZERO_ROW_TEST
     if (wsptr[1] == 0 && wsptr[2] == 0 && wsptr[3] == 0 &&
         wsptr[5] == 0 && wsptr[6] == 0 && wsptr[7] == 0) {
       /* AC terms all zero */
       JSAMPLE dcval = range_limit[(int) DESCALE((JLONG) wsptr[0], PASS1_BITS+3)
                                   & RANGE_MASK];

       outptr[0] = dcval;
       outptr[1] = dcval;
       outptr[2] = dcval;
       outptr[3] = dcval;

       wsptr += DCTSIZE;         /* advance pointer to next row */
       continue;
     }
 #endif

     /* Even part */

     tmp0 = LEFT_SHIFT((JLONG) wsptr[0], CONST_BITS+1);

     tmp2 = MULTIPLY((JLONG) wsptr[2], FIX_1_847759065)
          + MULTIPLY((JLONG) wsptr[6], - FIX_0_765366865);

     tmp10 = tmp0 + tmp2;
     tmp12 = tmp0 - tmp2;

     /* Odd part */

     z1 = (JLONG) wsptr[7];
     z2 = (JLONG) wsptr[5];
     z3 = (JLONG) wsptr[3];
     z4 = (JLONG) wsptr[1];

     tmp0 = MULTIPLY(z1, - FIX_0_211164243) /* sqrt(2) * (c3-c1) */
          + MULTIPLY(z2, FIX_1_451774981) /* sqrt(2) * (c3+c7) */
          + MULTIPLY(z3, - FIX_2_172734803) /* sqrt(2) * (-c1-c5) */
          + MULTIPLY(z4, FIX_1_061594337); /* sqrt(2) * (c5+c7) */

     tmp2 = MULTIPLY(z1, - FIX_0_509795579) /* sqrt(2) * (c7-c5) */
          + MULTIPLY(z2, - FIX_0_601344887) /* sqrt(2) * (c5-c1) */
          + MULTIPLY(z3, FIX_0_899976223) /* sqrt(2) * (c3-c7) */
          + MULTIPLY(z4, FIX_2_562915447); /* sqrt(2) * (c1+c3) */

     /* Final output stage */

     outptr[0] = range_limit[(int) DESCALE(tmp10 + tmp2,
                                           CONST_BITS+PASS1_BITS+3+1)
                             & RANGE_MASK];
     outptr[3] = range_limit[(int) DESCALE(tmp10 - tmp2,
                                           CONST_BITS+PASS1_BITS+3+1)
                             & RANGE_MASK];
     outptr[1] = range_limit[(int) DESCALE(tmp12 + tmp0,
                                           CONST_BITS+PASS1_BITS+3+1)
                             & RANGE_MASK];
     outptr[2] = range_limit[(int) DESCALE(tmp12 - tmp0,
                                           CONST_BITS+PASS1_BITS+3+1)
                             & RANGE_MASK];

     wsptr += DCTSIZE;           /* advance pointer to next row */
   }
 }


 /*
  * Perform dequantization and inverse DCT on one block of coefficients,
  * producing a reduced-size 2x2 output block.
  */

 GLOBAL(void)
 jpeg_idct_2x2 (j_decompress_ptr cinfo, jpeg_component_info *compptr,
                JCOEFPTR coef_block,
                JSAMPARRAY output_buf, JDIMENSION output_col)
 {
   JLONG tmp0, tmp10, z1;
   JCOEFPTR inptr;
   ISLOW_MULT_TYPE *quantptr;
   int *wsptr;
   JSAMPROW outptr;
   JSAMPLE *range_limit = IDCT_range_limit(cinfo);
   int ctr;
   int workspace[DCTSIZE*2];     /* buffers data between passes */
   SHIFT_TEMPS

   /* Pass 1: process columns from input, store into work array. */

   inptr = coef_block;
   quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
   wsptr = workspace;
   for (ctr = DCTSIZE; ctr > 0; inptr++, quantptr++, wsptr++, ctr--) {
     /* Don't bother to process columns 2,4,6 */
     if (ctr == DCTSIZE-2 || ctr == DCTSIZE-4 || ctr == DCTSIZE-6)
       continue;
     if (inptr[DCTSIZE*1] == 0 && inptr[DCTSIZE*3] == 0 &&
         inptr[DCTSIZE*5] == 0 && inptr[DCTSIZE*7] == 0) {
       /* AC terms all zero; we need not examine terms 2,4,6 for 2x2 output */
       int dcval = LEFT_SHIFT(DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]),
                              PASS1_BITS);

       wsptr[DCTSIZE*0] = dcval;
       wsptr[DCTSIZE*1] = dcval;

       continue;
     }

     /* Even part */

     z1 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]);
     tmp10 = LEFT_SHIFT(z1, CONST_BITS+2);

     /* Odd part */

     z1 = DEQUANTIZE(inptr[DCTSIZE*7], quantptr[DCTSIZE*7]);
     tmp0 = MULTIPLY(z1, - FIX_0_720959822); /* sqrt(2) * (c7-c5+c3-c1) */
     z1 = DEQUANTIZE(inptr[DCTSIZE*5], quantptr[DCTSIZE*5]);
     tmp0 += MULTIPLY(z1, FIX_0_850430095); /* sqrt(2) * (-c1+c3+c5+c7) */
     z1 = DEQUANTIZE(inptr[DCTSIZE*3], quantptr[DCTSIZE*3]);
     tmp0 += MULTIPLY(z1, - FIX_1_272758580); /* sqrt(2) * (-c1+c3-c5-c7) */
     z1 = DEQUANTIZE(inptr[DCTSIZE*1], quantptr[DCTSIZE*1]);
     tmp0 += MULTIPLY(z1, FIX_3_624509785); /* sqrt(2) * (c1+c3+c5+c7) */

     /* Final output stage */

     wsptr[DCTSIZE*0] = (int) DESCALE(tmp10 + tmp0, CONST_BITS-PASS1_BITS+2);
     wsptr[DCTSIZE*1] = (int) DESCALE(tmp10 - tmp0, CONST_BITS-PASS1_BITS+2);
   }

   /* Pass 2: process 2 rows from work array, store into output array. */

   wsptr = workspace;
   for (ctr = 0; ctr < 2; ctr++) {
     outptr = output_buf[ctr] + output_col;
     /* It's not clear whether a zero row test is worthwhile here ... */

 #ifndef NO_ZERO_ROW_TEST
     if (wsptr[1] == 0 && wsptr[3] == 0 && wsptr[5] == 0 && wsptr[7] == 0) {
       /* AC terms all zero */
       JSAMPLE dcval = range_limit[(int) DESCALE((JLONG) wsptr[0], PASS1_BITS+3)
                                   & RANGE_MASK];

       outptr[0] = dcval;
       outptr[1] = dcval;

       wsptr += DCTSIZE;         /* advance pointer to next row */
       continue;
     }
 #endif

     /* Even part */

     tmp10 = LEFT_SHIFT((JLONG) wsptr[0], CONST_BITS+2);

     /* Odd part */

     tmp0 = MULTIPLY((JLONG) wsptr[7], - FIX_0_720959822) /* sqrt(2) * (c7-c5+c3-c1) */
          + MULTIPLY((JLONG) wsptr[5], FIX_0_850430095) /* sqrt(2) * (-c1+c3+c5+c7) */
          + MULTIPLY((JLONG) wsptr[3], - FIX_1_272758580) /* sqrt(2) * (-c1+c3-c5-c7) */
          + MULTIPLY((JLONG) wsptr[1], FIX_3_624509785); /* sqrt(2) * (c1+c3+c5+c7) */

     /* Final output stage */

     outptr[0] = range_limit[(int) DESCALE(tmp10 + tmp0,
                                           CONST_BITS+PASS1_BITS+3+2)
                             & RANGE_MASK];
     outptr[1] = range_limit[(int) DESCALE(tmp10 - tmp0,
                                           CONST_BITS+PASS1_BITS+3+2)
                             & RANGE_MASK];

     wsptr += DCTSIZE;           /* advance pointer to next row */
   }
 }


 /*
  * Perform dequantization and inverse DCT on one block of coefficients,
  * producing a reduced-size 1x1 output block.
  */

 GLOBAL(void)
 jpeg_idct_1x1 (j_decompress_ptr cinfo, jpeg_component_info *compptr,
                JCOEFPTR coef_block,
                JSAMPARRAY output_buf, JDIMENSION output_col)
 {
   int dcval;
   ISLOW_MULT_TYPE *quantptr;
   JSAMPLE *range_limit = IDCT_range_limit(cinfo);
   SHIFT_TEMPS

   /* We hardly need an inverse DCT routine for this: just take the
    * average pixel value, which is one-eighth of the DC coefficient.
    */
   quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
   dcval = DEQUANTIZE(coef_block[0], quantptr[0]);
   dcval = (int) DESCALE((JLONG) dcval, 3);

   output_buf[0][output_col] = range_limit[dcval & RANGE_MASK];
 }

 #endif /* IDCT_SCALING_SUPPORTED */
	/*
	* jidctred.c
	*
	* This file was part of the Independent JPEG Group's software.
	* Copyright (C) 1994-1998, Thomas G. Lane.
	* libjpeg-turbo Modifications:
	* Copyright (C) 2015, D. R. Commander
	* For conditions of distribution and use, see the accompanying README.ijg
	* file.
	*
	* This file contains inverse-DCT routines that produce reduced-size output:
	* either 4x4, 2x2, or 1x1 pixels from an 8x8 DCT block.
	*
	* The implementation is based on the Loeffler, Ligtenberg and Moschytz (LL&M)
	* algorithm used in jidctint.c. We simply replace each 8-to-8 1-D IDCT step
	* with an 8-to-4 step that produces the four averages of two adjacent outputs
	* (or an 8-to-2 step producing two averages of four outputs, for 2x2 output).
	* These steps were derived by computing the corresponding values at the end
	* of the normal LL&M code, then simplifying as much as possible.
	*
	* 1x1 is trivial: just take the DC coefficient divided by 8.
	*
	* See jidctint.c for additional comments.
	*/

	#define JPEG_INTERNALS
	#include "jinclude.h"
	#include "jpeglib.h"
	#include "jdct.h" /* Private declarations for DCT subsystem */

	#ifdef IDCT_SCALING_SUPPORTED


	/*
	* This module is specialized to the case DCTSIZE = 8.
	*/

	#if DCTSIZE != 8
	Sorry, this code only copes with 8x8 DCTs. /* deliberate syntax err */
	#endif


	/* Scaling is the same as in jidctint.c. */

	#if BITS_IN_JSAMPLE == 8
	#define CONST_BITS 13
	#define PASS1_BITS 2
	#else
	#define CONST_BITS 13
	#define PASS1_BITS 1 /* lose a little precision to avoid overflow */
	#endif

	/* Some C compilers fail to reduce "FIX(constant)" at compile time, thus
	* causing a lot of useless floating-point operations at run time.
	* To get around this we use the following pre-calculated constants.
	* If you change CONST_BITS you may want to add appropriate values.
	* (With a reasonable C compiler, you can just rely on the FIX() macro...)
	*/

	#if CONST_BITS == 13
	#define FIX_0_211164243 ((JLONG) 1730) /* FIX(0.211164243) */
	#define FIX_0_509795579 ((JLONG) 4176) /* FIX(0.509795579) */
	#define FIX_0_601344887 ((JLONG) 4926) /* FIX(0.601344887) */
	#define FIX_0_720959822 ((JLONG) 5906) /* FIX(0.720959822) */
	#define FIX_0_765366865 ((JLONG) 6270) /* FIX(0.765366865) */
	#define FIX_0_850430095 ((JLONG) 6967) /* FIX(0.850430095) */
	#define FIX_0_899976223 ((JLONG) 7373) /* FIX(0.899976223) */
	#define FIX_1_061594337 ((JLONG) 8697) /* FIX(1.061594337) */
	#define FIX_1_272758580 ((JLONG) 10426) /* FIX(1.272758580) */
	#define FIX_1_451774981 ((JLONG) 11893) /* FIX(1.451774981) */
	#define FIX_1_847759065 ((JLONG) 15137) /* FIX(1.847759065) */
	#define FIX_2_172734803 ((JLONG) 17799) /* FIX(2.172734803) */
	#define FIX_2_562915447 ((JLONG) 20995) /* FIX(2.562915447) */
	#define FIX_3_624509785 ((JLONG) 29692) /* FIX(3.624509785) */
	#else
	#define FIX_0_211164243 FIX(0.211164243)
	#define FIX_0_509795579 FIX(0.509795579)
	#define FIX_0_601344887 FIX(0.601344887)
	#define FIX_0_720959822 FIX(0.720959822)
	#define FIX_0_765366865 FIX(0.765366865)
	#define FIX_0_850430095 FIX(0.850430095)
	#define FIX_0_899976223 FIX(0.899976223)
	#define FIX_1_061594337 FIX(1.061594337)
	#define FIX_1_272758580 FIX(1.272758580)
	#define FIX_1_451774981 FIX(1.451774981)
	#define FIX_1_847759065 FIX(1.847759065)
	#define FIX_2_172734803 FIX(2.172734803)
	#define FIX_2_562915447 FIX(2.562915447)
	#define FIX_3_624509785 FIX(3.624509785)
	#endif


	/* Multiply a JLONG variable by a JLONG constant to yield a JLONG result.
	* For 8-bit samples with the recommended scaling, all the variable
	* and constant values involved are no more than 16 bits wide, so a
	* 16x16->32 bit multiply can be used instead of a full 32x32 multiply.
	* For 12-bit samples, a full 32-bit multiplication will be needed.
	*/

	#if BITS_IN_JSAMPLE == 8
	#define MULTIPLY(var,const) MULTIPLY16C16(var,const)
	#else
	#define MULTIPLY(var,const) ((var) * (const))
	#endif


	/* Dequantize a coefficient by multiplying it by the multiplier-table
	* entry; produce an int result. In this module, both inputs and result
	* are 16 bits or less, so either int or short multiply will work.
	*/

	#define DEQUANTIZE(coef,quantval) (((ISLOW_MULT_TYPE) (coef)) * (quantval))


	/*
	* Perform dequantization and inverse DCT on one block of coefficients,
	* producing a reduced-size 4x4 output block.
	*/

	GLOBAL(void)
	jpeg_idct_4x4 (j_decompress_ptr cinfo, jpeg_component_info *compptr,
	JCOEFPTR coef_block,
	JSAMPARRAY output_buf, JDIMENSION output_col)
	{
	JLONG tmp0, tmp2, tmp10, tmp12;
	JLONG z1, z2, z3, z4;
	JCOEFPTR inptr;
	ISLOW_MULT_TYPE *quantptr;
	int *wsptr;
	JSAMPROW outptr;
	JSAMPLE *range_limit = IDCT_range_limit(cinfo);
	int ctr;
	int workspace[DCTSIZE4]; / buffers data between passes */
	SHIFT_TEMPS

	/* Pass 1: process columns from input, store into work array. */

	inptr = coef_block;
	quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
	wsptr = workspace;
	for (ctr = DCTSIZE; ctr > 0; inptr++, quantptr++, wsptr++, ctr--) {
	/* Don't bother to process column 4, because second pass won't use it */
	if (ctr == DCTSIZE-4)
	continue;
	if (inptr[DCTSIZE1] == 0 && inptr[DCTSIZE2] == 0 &&
	inptr[DCTSIZE3] == 0 && inptr[DCTSIZE5] == 0 &&
	inptr[DCTSIZE6] == 0 && inptr[DCTSIZE7] == 0) {
	/* AC terms all zero; we need not examine term 4 for 4x4 output */
	int dcval = LEFT_SHIFT(DEQUANTIZE(inptr[DCTSIZE0], quantptr[DCTSIZE0]),
	PASS1_BITS);

	wsptr[DCTSIZE*0] = dcval;
	wsptr[DCTSIZE*1] = dcval;
	wsptr[DCTSIZE*2] = dcval;
	wsptr[DCTSIZE*3] = dcval;

	continue;
	}

	/* Even part */

	tmp0 = DEQUANTIZE(inptr[DCTSIZE0], quantptr[DCTSIZE0]);
	tmp0 = LEFT_SHIFT(tmp0, CONST_BITS+1);

	z2 = DEQUANTIZE(inptr[DCTSIZE2], quantptr[DCTSIZE2]);
	z3 = DEQUANTIZE(inptr[DCTSIZE6], quantptr[DCTSIZE6]);

	tmp2 = MULTIPLY(z2, FIX_1_847759065) + MULTIPLY(z3, - FIX_0_765366865);

	tmp10 = tmp0 + tmp2;
	tmp12 = tmp0 - tmp2;

	/* Odd part */

	z1 = DEQUANTIZE(inptr[DCTSIZE7], quantptr[DCTSIZE7]);
	z2 = DEQUANTIZE(inptr[DCTSIZE5], quantptr[DCTSIZE5]);
	z3 = DEQUANTIZE(inptr[DCTSIZE3], quantptr[DCTSIZE3]);
	z4 = DEQUANTIZE(inptr[DCTSIZE1], quantptr[DCTSIZE1]);

	tmp0 = MULTIPLY(z1, - FIX_0_211164243) /* sqrt(2) * (c3-c1) */
	+ MULTIPLY(z2, FIX_1_451774981) /* sqrt(2) * (c3+c7) */
	+ MULTIPLY(z3, - FIX_2_172734803) /* sqrt(2) * (-c1-c5) */
	+ MULTIPLY(z4, FIX_1_061594337); /* sqrt(2) * (c5+c7) */

	tmp2 = MULTIPLY(z1, - FIX_0_509795579) /* sqrt(2) * (c7-c5) */
	+ MULTIPLY(z2, - FIX_0_601344887) /* sqrt(2) * (c5-c1) */
	+ MULTIPLY(z3, FIX_0_899976223) /* sqrt(2) * (c3-c7) */
	+ MULTIPLY(z4, FIX_2_562915447); /* sqrt(2) * (c1+c3) */

	/* Final output stage */

	wsptr[DCTSIZE*0] = (int) DESCALE(tmp10 + tmp2, CONST_BITS-PASS1_BITS+1);
	wsptr[DCTSIZE*3] = (int) DESCALE(tmp10 - tmp2, CONST_BITS-PASS1_BITS+1);
	wsptr[DCTSIZE*1] = (int) DESCALE(tmp12 + tmp0, CONST_BITS-PASS1_BITS+1);
	wsptr[DCTSIZE*2] = (int) DESCALE(tmp12 - tmp0, CONST_BITS-PASS1_BITS+1);
	}

	/* Pass 2: process 4 rows from work array, store into output array. */

	wsptr = workspace;
	for (ctr = 0; ctr < 4; ctr++) {
	outptr = output_buf[ctr] + output_col;
	/* It's not clear whether a zero row test is worthwhile here ... */

	#ifndef NO_ZERO_ROW_TEST
	if (wsptr[1] == 0 && wsptr[2] == 0 && wsptr[3] == 0 &&
	wsptr[5] == 0 && wsptr[6] == 0 && wsptr[7] == 0) {
	/* AC terms all zero */
	JSAMPLE dcval = range_limit[(int) DESCALE((JLONG) wsptr[0], PASS1_BITS+3)
	& RANGE_MASK];

	outptr[0] = dcval;
	outptr[1] = dcval;
	outptr[2] = dcval;
	outptr[3] = dcval;

	wsptr += DCTSIZE; /* advance pointer to next row */
	continue;
	}
	#endif

	/* Even part */

	tmp0 = LEFT_SHIFT((JLONG) wsptr[0], CONST_BITS+1);

	tmp2 = MULTIPLY((JLONG) wsptr[2], FIX_1_847759065)
	+ MULTIPLY((JLONG) wsptr[6], - FIX_0_765366865);

	tmp10 = tmp0 + tmp2;
	tmp12 = tmp0 - tmp2;

	/* Odd part */

	z1 = (JLONG) wsptr[7];
	z2 = (JLONG) wsptr[5];
	z3 = (JLONG) wsptr[3];
	z4 = (JLONG) wsptr[1];

	tmp0 = MULTIPLY(z1, - FIX_0_211164243) /* sqrt(2) * (c3-c1) */
	+ MULTIPLY(z2, FIX_1_451774981) /* sqrt(2) * (c3+c7) */
	+ MULTIPLY(z3, - FIX_2_172734803) /* sqrt(2) * (-c1-c5) */
	+ MULTIPLY(z4, FIX_1_061594337); /* sqrt(2) * (c5+c7) */

	tmp2 = MULTIPLY(z1, - FIX_0_509795579) /* sqrt(2) * (c7-c5) */
	+ MULTIPLY(z2, - FIX_0_601344887) /* sqrt(2) * (c5-c1) */
	+ MULTIPLY(z3, FIX_0_899976223) /* sqrt(2) * (c3-c7) */
	+ MULTIPLY(z4, FIX_2_562915447); /* sqrt(2) * (c1+c3) */

	/* Final output stage */

	outptr[0] = range_limit[(int) DESCALE(tmp10 + tmp2,
	CONST_BITS+PASS1_BITS+3+1)
	& RANGE_MASK];
	outptr[3] = range_limit[(int) DESCALE(tmp10 - tmp2,
	CONST_BITS+PASS1_BITS+3+1)
	& RANGE_MASK];
	outptr[1] = range_limit[(int) DESCALE(tmp12 + tmp0,
	CONST_BITS+PASS1_BITS+3+1)
	& RANGE_MASK];
	outptr[2] = range_limit[(int) DESCALE(tmp12 - tmp0,
	CONST_BITS+PASS1_BITS+3+1)
	& RANGE_MASK];

	wsptr += DCTSIZE; /* advance pointer to next row */
	}
	}


	/*
	* Perform dequantization and inverse DCT on one block of coefficients,
	* producing a reduced-size 2x2 output block.
	*/

	GLOBAL(void)
	jpeg_idct_2x2 (j_decompress_ptr cinfo, jpeg_component_info *compptr,
	JCOEFPTR coef_block,
	JSAMPARRAY output_buf, JDIMENSION output_col)
	{
	JLONG tmp0, tmp10, z1;
	JCOEFPTR inptr;
	ISLOW_MULT_TYPE *quantptr;
	int *wsptr;
	JSAMPROW outptr;
	JSAMPLE *range_limit = IDCT_range_limit(cinfo);
	int ctr;
	int workspace[DCTSIZE2]; / buffers data between passes */
	SHIFT_TEMPS

	/* Pass 1: process columns from input, store into work array. */

	inptr = coef_block;
	quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
	wsptr = workspace;
	for (ctr = DCTSIZE; ctr > 0; inptr++, quantptr++, wsptr++, ctr--) {
	/* Don't bother to process columns 2,4,6 */
	if (ctr == DCTSIZE-2 \|\| ctr == DCTSIZE-4 \|\| ctr == DCTSIZE-6)
	continue;
	if (inptr[DCTSIZE1] == 0 && inptr[DCTSIZE3] == 0 &&
	inptr[DCTSIZE5] == 0 && inptr[DCTSIZE7] == 0) {
	/* AC terms all zero; we need not examine terms 2,4,6 for 2x2 output */
	int dcval = LEFT_SHIFT(DEQUANTIZE(inptr[DCTSIZE0], quantptr[DCTSIZE0]),
	PASS1_BITS);

	wsptr[DCTSIZE*0] = dcval;
	wsptr[DCTSIZE*1] = dcval;

	continue;
	}

	/* Even part */

	z1 = DEQUANTIZE(inptr[DCTSIZE0], quantptr[DCTSIZE0]);
	tmp10 = LEFT_SHIFT(z1, CONST_BITS+2);

	/* Odd part */

	z1 = DEQUANTIZE(inptr[DCTSIZE7], quantptr[DCTSIZE7]);
	tmp0 = MULTIPLY(z1, - FIX_0_720959822); /* sqrt(2) * (c7-c5+c3-c1) */
	z1 = DEQUANTIZE(inptr[DCTSIZE5], quantptr[DCTSIZE5]);
	tmp0 += MULTIPLY(z1, FIX_0_850430095); /* sqrt(2) * (-c1+c3+c5+c7) */
	z1 = DEQUANTIZE(inptr[DCTSIZE3], quantptr[DCTSIZE3]);
	tmp0 += MULTIPLY(z1, - FIX_1_272758580); /* sqrt(2) * (-c1+c3-c5-c7) */
	z1 = DEQUANTIZE(inptr[DCTSIZE1], quantptr[DCTSIZE1]);
	tmp0 += MULTIPLY(z1, FIX_3_624509785); /* sqrt(2) * (c1+c3+c5+c7) */

	/* Final output stage */

	wsptr[DCTSIZE*0] = (int) DESCALE(tmp10 + tmp0, CONST_BITS-PASS1_BITS+2);
	wsptr[DCTSIZE*1] = (int) DESCALE(tmp10 - tmp0, CONST_BITS-PASS1_BITS+2);
	}

	/* Pass 2: process 2 rows from work array, store into output array. */

	wsptr = workspace;
	for (ctr = 0; ctr < 2; ctr++) {
	outptr = output_buf[ctr] + output_col;
	/* It's not clear whether a zero row test is worthwhile here ... */

	#ifndef NO_ZERO_ROW_TEST
	if (wsptr[1] == 0 && wsptr[3] == 0 && wsptr[5] == 0 && wsptr[7] == 0) {
	/* AC terms all zero */
	JSAMPLE dcval = range_limit[(int) DESCALE((JLONG) wsptr[0], PASS1_BITS+3)
	& RANGE_MASK];

	outptr[0] = dcval;
	outptr[1] = dcval;

	wsptr += DCTSIZE; /* advance pointer to next row */
	continue;
	}
	#endif

	/* Even part */

	tmp10 = LEFT_SHIFT((JLONG) wsptr[0], CONST_BITS+2);

	/* Odd part */

	tmp0 = MULTIPLY((JLONG) wsptr[7], - FIX_0_720959822) /* sqrt(2) * (c7-c5+c3-c1) */
	+ MULTIPLY((JLONG) wsptr[5], FIX_0_850430095) /* sqrt(2) * (-c1+c3+c5+c7) */
	+ MULTIPLY((JLONG) wsptr[3], - FIX_1_272758580) /* sqrt(2) * (-c1+c3-c5-c7) */
	+ MULTIPLY((JLONG) wsptr[1], FIX_3_624509785); /* sqrt(2) * (c1+c3+c5+c7) */

	/* Final output stage */

	outptr[0] = range_limit[(int) DESCALE(tmp10 + tmp0,
	CONST_BITS+PASS1_BITS+3+2)
	& RANGE_MASK];
	outptr[1] = range_limit[(int) DESCALE(tmp10 - tmp0,
	CONST_BITS+PASS1_BITS+3+2)
	& RANGE_MASK];

	wsptr += DCTSIZE; /* advance pointer to next row */
	}
	}


	/*
	* Perform dequantization and inverse DCT on one block of coefficients,
	* producing a reduced-size 1x1 output block.
	*/

	GLOBAL(void)
	jpeg_idct_1x1 (j_decompress_ptr cinfo, jpeg_component_info *compptr,
	JCOEFPTR coef_block,
	JSAMPARRAY output_buf, JDIMENSION output_col)
	{
	int dcval;
	ISLOW_MULT_TYPE *quantptr;
	JSAMPLE *range_limit = IDCT_range_limit(cinfo);
	SHIFT_TEMPS

	/* We hardly need an inverse DCT routine for this: just take the
	* average pixel value, which is one-eighth of the DC coefficient.
	*/
	quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
	dcval = DEQUANTIZE(coef_block[0], quantptr[0]);
	dcval = (int) DESCALE((JLONG) dcval, 3);

	output_buf[0][output_col] = range_limit[dcval & RANGE_MASK];
	}

	#endif /* IDCT_SCALING_SUPPORTED */