src/third_party/libjpeg/jdmerge.c - cobalt - Git at Google

 /*
  * jdmerge.c
  *
  * Copyright (C) 1994-1996, Thomas G. Lane.
  * 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 code for merged upsampling/color conversion.
  *
  * This file combines functions from jdsample.c and jdcolor.c;
  * read those files first to understand what's going on.
  *
  * When the chroma components are to be upsampled by simple replication
  * (ie, box filtering), we can save some work in color conversion by
  * calculating all the output pixels corresponding to a pair of chroma
  * samples at one time.  In the conversion equations
  *	R = Y           + K1 * Cr
  *	G = Y + K2 * Cb + K3 * Cr
  *	B = Y + K4 * Cb
  * only the Y term varies among the group of pixels corresponding to a pair
  * of chroma samples, so the rest of the terms can be calculated just once.
  * At typical sampling ratios, this eliminates half or three-quarters of the
  * multiplications needed for color conversion.
  *
  * This file currently provides implementations for the following cases:
  *	YCbCr => RGB color conversion only.
  *	Sampling ratios of 2h1v or 2h2v.
  *	No scaling needed at upsample time.
  *	Corner-aligned (non-CCIR601) sampling alignment.
  * Other special cases could be added, but in most applications these are
  * the only common cases.  (For uncommon cases we fall back on the more
  * general code in jdsample.c and jdcolor.c.)
  */

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

 #ifdef UPSAMPLE_MERGING_SUPPORTED


 /* Private subobject */

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

   /* Pointer to routine to do actual upsampling/conversion of one row group */
   JMETHOD(void, upmethod, (j_decompress_ptr cinfo,
 			   JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr,
 			   JSAMPARRAY output_buf));

   /* Private state for YCC->RGB conversion */
   int * Cr_r_tab;		/* => table for Cr to R conversion */
   int * Cb_b_tab;		/* => table for Cb to B conversion */
   INT32 * Cr_g_tab;		/* => table for Cr to G conversion */
   INT32 * Cb_g_tab;		/* => table for Cb to G conversion */

   /* For 2:1 vertical sampling, we produce two output rows at a time.
    * We need a "spare" row buffer to hold the second output row if the
    * application provides just a one-row buffer; we also use the spare
    * to discard the dummy last row if the image height is odd.
    */
   JSAMPROW spare_row;
   boolean spare_full;		/* T if spare buffer is occupied */

   JDIMENSION out_row_width;	/* samples per output row */
   JDIMENSION rows_to_go;	/* counts rows remaining in image */
 } my_upsampler;

 typedef my_upsampler * my_upsample_ptr;

 #define SCALEBITS	16	/* speediest right-shift on some machines */
 #define ONE_HALF	((INT32) 1 << (SCALEBITS-1))
 #define FIX(x)		((INT32) ((x) * (1L<<SCALEBITS) + 0.5))


 /*
  * Initialize tables for YCC->RGB colorspace conversion.
  * This is taken directly from jdcolor.c; see that file for more info.
  */

 LOCAL(void)
 build_ycc_rgb_table (j_decompress_ptr cinfo)
 {
   my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
   int i;
   INT32 x;
   SHIFT_TEMPS

   upsample->Cr_r_tab = (int *)
     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 				(MAXJSAMPLE+1) * SIZEOF(int));
   upsample->Cb_b_tab = (int *)
     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 				(MAXJSAMPLE+1) * SIZEOF(int));
   upsample->Cr_g_tab = (INT32 *)
     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 				(MAXJSAMPLE+1) * SIZEOF(INT32));
   upsample->Cb_g_tab = (INT32 *)
     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 				(MAXJSAMPLE+1) * SIZEOF(INT32));

   for (i = 0, x = -CENTERJSAMPLE; i <= MAXJSAMPLE; i++, x++) {
     /* i is the actual input pixel value, in the range 0..MAXJSAMPLE */
     /* The Cb or Cr value we are thinking of is x = i - CENTERJSAMPLE */
     /* Cr=>R value is nearest int to 1.40200 * x */
     upsample->Cr_r_tab[i] = (int)
 		    RIGHT_SHIFT(FIX(1.40200) * x + ONE_HALF, SCALEBITS);
     /* Cb=>B value is nearest int to 1.77200 * x */
     upsample->Cb_b_tab[i] = (int)
 		    RIGHT_SHIFT(FIX(1.77200) * x + ONE_HALF, SCALEBITS);
     /* Cr=>G value is scaled-up -0.71414 * x */
     upsample->Cr_g_tab[i] = (- FIX(0.71414)) * x;
     /* Cb=>G value is scaled-up -0.34414 * x */
     /* We also add in ONE_HALF so that need not do it in inner loop */
     upsample->Cb_g_tab[i] = (- FIX(0.34414)) * x + ONE_HALF;
   }
 }


 /*
  * Initialize for an upsampling pass.
  */

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

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


 /*
  * Control routine to do upsampling (and color conversion).
  *
  * The control routine just handles the row buffering considerations.
  */

 METHODDEF(void)
 merged_2v_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)
 /* 2:1 vertical sampling case: may need a spare row. */
 {
   my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
   JSAMPROW work_ptrs[2];
   JDIMENSION num_rows;		/* number of rows returned to caller */

   if (upsample->spare_full) {
     /* If we have a spare row saved from a previous cycle, just return it. */
     jcopy_sample_rows(& upsample->spare_row, 0, output_buf + *out_row_ctr, 0,
 		      1, upsample->out_row_width);
     num_rows = 1;
     upsample->spare_full = FALSE;
   } else {
     /* Figure number of rows to return to caller. */
     num_rows = 2;
     /* Not more than the distance to the end of the image. */
     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;
     /* Create output pointer array for upsampler. */
     work_ptrs[0] = output_buf[*out_row_ctr];
     if (num_rows > 1) {
       work_ptrs[1] = output_buf[*out_row_ctr + 1];
     } else {
       work_ptrs[1] = upsample->spare_row;
       upsample->spare_full = TRUE;
     }
     /* Now do the upsampling. */
     (*upsample->upmethod) (cinfo, input_buf, *in_row_group_ctr, work_ptrs);
   }

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


 METHODDEF(void)
 merged_1v_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)
 /* 1:1 vertical sampling case: much easier, never need a spare row. */
 {
   my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;

   /* Just do the upsampling. */
   (*upsample->upmethod) (cinfo, input_buf, *in_row_group_ctr,
 			 output_buf + *out_row_ctr);
   /* Adjust counts */
   (*out_row_ctr)++;
   (*in_row_group_ctr)++;
 }


 /*
  * These are the routines invoked by the control routines to do
  * the actual upsampling/conversion.  One row group is processed per call.
  *
  * Note: since we may be writing directly into application-supplied buffers,
  * we have to be honest about the output width; we can't assume the buffer
  * has been rounded up to an even width.
  */


 /*
  * Upsample and color convert for the case of 2:1 horizontal and 1:1 vertical.
  */

 METHODDEF(void)
 h2v1_merged_upsample (j_decompress_ptr cinfo,
 		      JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr,
 		      JSAMPARRAY output_buf)
 {
   my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
   register int y, cred, cgreen, cblue;
   int cb, cr;
   register JSAMPROW outptr;
   JSAMPROW inptr0, inptr1, inptr2;
   JDIMENSION col;
   /* copy these pointers into registers if possible */
   register JSAMPLE * range_limit = cinfo->sample_range_limit;
   int * Crrtab = upsample->Cr_r_tab;
   int * Cbbtab = upsample->Cb_b_tab;
   INT32 * Crgtab = upsample->Cr_g_tab;
   INT32 * Cbgtab = upsample->Cb_g_tab;
   SHIFT_TEMPS

   inptr0 = input_buf[0][in_row_group_ctr];
   inptr1 = input_buf[1][in_row_group_ctr];
   inptr2 = input_buf[2][in_row_group_ctr];
   outptr = output_buf[0];
   /* Loop for each pair of output pixels */
   for (col = cinfo->output_width >> 1; col > 0; col--) {
     /* Do the chroma part of the calculation */
     cb = GETJSAMPLE(*inptr1++);
     cr = GETJSAMPLE(*inptr2++);
     cred = Crrtab[cr];
     cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
     cblue = Cbbtab[cb];
     /* Fetch 2 Y values and emit 2 pixels */
     y  = GETJSAMPLE(*inptr0++);
     outptr[RGB_RED] =   range_limit[y + cred];
     outptr[RGB_GREEN] = range_limit[y + cgreen];
     outptr[RGB_BLUE] =  range_limit[y + cblue];
     outptr += RGB_PIXELSIZE;
     y  = GETJSAMPLE(*inptr0++);
     outptr[RGB_RED] =   range_limit[y + cred];
     outptr[RGB_GREEN] = range_limit[y + cgreen];
     outptr[RGB_BLUE] =  range_limit[y + cblue];
     outptr += RGB_PIXELSIZE;
   }
   /* If image width is odd, do the last output column separately */
   if (cinfo->output_width & 1) {
     cb = GETJSAMPLE(*inptr1);
     cr = GETJSAMPLE(*inptr2);
     cred = Crrtab[cr];
     cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
     cblue = Cbbtab[cb];
     y  = GETJSAMPLE(*inptr0);
     outptr[RGB_RED] =   range_limit[y + cred];
     outptr[RGB_GREEN] = range_limit[y + cgreen];
     outptr[RGB_BLUE] =  range_limit[y + cblue];
   }
 }


 /*
  * Upsample and color convert for the case of 2:1 horizontal and 2:1 vertical.
  */

 METHODDEF(void)
 h2v2_merged_upsample (j_decompress_ptr cinfo,
 		      JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr,
 		      JSAMPARRAY output_buf)
 {
   my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
   register int y, cred, cgreen, cblue;
   int cb, cr;
   register JSAMPROW outptr0, outptr1;
   JSAMPROW inptr00, inptr01, inptr1, inptr2;
   JDIMENSION col;
   /* copy these pointers into registers if possible */
   register JSAMPLE * range_limit = cinfo->sample_range_limit;
   int * Crrtab = upsample->Cr_r_tab;
   int * Cbbtab = upsample->Cb_b_tab;
   INT32 * Crgtab = upsample->Cr_g_tab;
   INT32 * Cbgtab = upsample->Cb_g_tab;
   SHIFT_TEMPS

   inptr00 = input_buf[0][in_row_group_ctr*2];
   inptr01 = input_buf[0][in_row_group_ctr*2 + 1];
   inptr1 = input_buf[1][in_row_group_ctr];
   inptr2 = input_buf[2][in_row_group_ctr];
   outptr0 = output_buf[0];
   outptr1 = output_buf[1];
   /* Loop for each group of output pixels */
   for (col = cinfo->output_width >> 1; col > 0; col--) {
     /* Do the chroma part of the calculation */
     cb = GETJSAMPLE(*inptr1++);
     cr = GETJSAMPLE(*inptr2++);
     cred = Crrtab[cr];
     cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
     cblue = Cbbtab[cb];
     /* Fetch 4 Y values and emit 4 pixels */
     y  = GETJSAMPLE(*inptr00++);
     outptr0[RGB_RED] =   range_limit[y + cred];
     outptr0[RGB_GREEN] = range_limit[y + cgreen];
     outptr0[RGB_BLUE] =  range_limit[y + cblue];
     outptr0 += RGB_PIXELSIZE;
     y  = GETJSAMPLE(*inptr00++);
     outptr0[RGB_RED] =   range_limit[y + cred];
     outptr0[RGB_GREEN] = range_limit[y + cgreen];
     outptr0[RGB_BLUE] =  range_limit[y + cblue];
     outptr0 += RGB_PIXELSIZE;
     y  = GETJSAMPLE(*inptr01++);
     outptr1[RGB_RED] =   range_limit[y + cred];
     outptr1[RGB_GREEN] = range_limit[y + cgreen];
     outptr1[RGB_BLUE] =  range_limit[y + cblue];
     outptr1 += RGB_PIXELSIZE;
     y  = GETJSAMPLE(*inptr01++);
     outptr1[RGB_RED] =   range_limit[y + cred];
     outptr1[RGB_GREEN] = range_limit[y + cgreen];
     outptr1[RGB_BLUE] =  range_limit[y + cblue];
     outptr1 += RGB_PIXELSIZE;
   }
   /* If image width is odd, do the last output column separately */
   if (cinfo->output_width & 1) {
     cb = GETJSAMPLE(*inptr1);
     cr = GETJSAMPLE(*inptr2);
     cred = Crrtab[cr];
     cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
     cblue = Cbbtab[cb];
     y  = GETJSAMPLE(*inptr00);
     outptr0[RGB_RED] =   range_limit[y + cred];
     outptr0[RGB_GREEN] = range_limit[y + cgreen];
     outptr0[RGB_BLUE] =  range_limit[y + cblue];
     y  = GETJSAMPLE(*inptr01);
     outptr1[RGB_RED] =   range_limit[y + cred];
     outptr1[RGB_GREEN] = range_limit[y + cgreen];
     outptr1[RGB_BLUE] =  range_limit[y + cblue];
   }
 }


 /*
  * Module initialization routine for merged upsampling/color conversion.
  *
  * NB: this is called under the conditions determined by use_merged_upsample()
  * in jdmaster.c.  That routine MUST correspond to the actual capabilities
  * of this module; no safety checks are made here.
  */

 GLOBAL(void)
 jinit_merged_upsampler (j_decompress_ptr cinfo)
 {
   my_upsample_ptr upsample;

   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_merged_upsample;
   upsample->pub.need_context_rows = FALSE;

   upsample->out_row_width = cinfo->output_width * cinfo->out_color_components;

   if (cinfo->max_v_samp_factor == 2) {
     upsample->pub.upsample = merged_2v_upsample;
     upsample->upmethod = h2v2_merged_upsample;
     /* Allocate a spare row buffer */
     upsample->spare_row = (JSAMPROW)
       (*cinfo->mem->alloc_large) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 		(size_t) (upsample->out_row_width * SIZEOF(JSAMPLE)));
   } else {
     upsample->pub.upsample = merged_1v_upsample;
     upsample->upmethod = h2v1_merged_upsample;
     /* No spare row needed */
     upsample->spare_row = NULL;
   }

   build_ycc_rgb_table(cinfo);
 }

 #endif /* UPSAMPLE_MERGING_SUPPORTED */
	/*
	* jdmerge.c
	*
	* Copyright (C) 1994-1996, Thomas G. Lane.
	* 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 code for merged upsampling/color conversion.
	*
	* This file combines functions from jdsample.c and jdcolor.c;
	* read those files first to understand what's going on.
	*
	* When the chroma components are to be upsampled by simple replication
	* (ie, box filtering), we can save some work in color conversion by
	* calculating all the output pixels corresponding to a pair of chroma
	* samples at one time. In the conversion equations
	* R = Y + K1 * Cr
	* G = Y + K2 * Cb + K3 * Cr
	* B = Y + K4 * Cb
	* only the Y term varies among the group of pixels corresponding to a pair
	* of chroma samples, so the rest of the terms can be calculated just once.
	* At typical sampling ratios, this eliminates half or three-quarters of the
	* multiplications needed for color conversion.
	*
	* This file currently provides implementations for the following cases:
	* YCbCr => RGB color conversion only.
	* Sampling ratios of 2h1v or 2h2v.
	* No scaling needed at upsample time.
	* Corner-aligned (non-CCIR601) sampling alignment.
	* Other special cases could be added, but in most applications these are
	* the only common cases. (For uncommon cases we fall back on the more
	* general code in jdsample.c and jdcolor.c.)
	*/

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

	#ifdef UPSAMPLE_MERGING_SUPPORTED


	/* Private subobject */

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

	/* Pointer to routine to do actual upsampling/conversion of one row group */
	JMETHOD(void, upmethod, (j_decompress_ptr cinfo,
	JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr,
	JSAMPARRAY output_buf));

	/* Private state for YCC->RGB conversion */
	int * Cr_r_tab; /* => table for Cr to R conversion */
	int * Cb_b_tab; /* => table for Cb to B conversion */
	INT32 * Cr_g_tab; /* => table for Cr to G conversion */
	INT32 * Cb_g_tab; /* => table for Cb to G conversion */

	/* For 2:1 vertical sampling, we produce two output rows at a time.
	* We need a "spare" row buffer to hold the second output row if the
	* application provides just a one-row buffer; we also use the spare
	* to discard the dummy last row if the image height is odd.
	*/
	JSAMPROW spare_row;
	boolean spare_full; /* T if spare buffer is occupied */

	JDIMENSION out_row_width; /* samples per output row */
	JDIMENSION rows_to_go; /* counts rows remaining in image */
	} my_upsampler;

	typedef my_upsampler * my_upsample_ptr;

	#define SCALEBITS 16 /* speediest right-shift on some machines */
	#define ONE_HALF ((INT32) 1 << (SCALEBITS-1))
	#define FIX(x) ((INT32) ((x) * (1L<<SCALEBITS) + 0.5))


	/*
	* Initialize tables for YCC->RGB colorspace conversion.
	* This is taken directly from jdcolor.c; see that file for more info.
	*/

	LOCAL(void)
	build_ycc_rgb_table (j_decompress_ptr cinfo)
	{
	my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
	int i;
	INT32 x;
	SHIFT_TEMPS

	upsample->Cr_r_tab = (int *)
	(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
	(MAXJSAMPLE+1) * SIZEOF(int));
	upsample->Cb_b_tab = (int *)
	(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
	(MAXJSAMPLE+1) * SIZEOF(int));
	upsample->Cr_g_tab = (INT32 *)
	(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
	(MAXJSAMPLE+1) * SIZEOF(INT32));
	upsample->Cb_g_tab = (INT32 *)
	(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
	(MAXJSAMPLE+1) * SIZEOF(INT32));

	for (i = 0, x = -CENTERJSAMPLE; i <= MAXJSAMPLE; i++, x++) {
	/* i is the actual input pixel value, in the range 0..MAXJSAMPLE */
	/* The Cb or Cr value we are thinking of is x = i - CENTERJSAMPLE */
	/* Cr=>R value is nearest int to 1.40200 * x */
	upsample->Cr_r_tab[i] = (int)
	RIGHT_SHIFT(FIX(1.40200) * x + ONE_HALF, SCALEBITS);
	/* Cb=>B value is nearest int to 1.77200 * x */
	upsample->Cb_b_tab[i] = (int)
	RIGHT_SHIFT(FIX(1.77200) * x + ONE_HALF, SCALEBITS);
	/* Cr=>G value is scaled-up -0.71414 * x */
	upsample->Cr_g_tab[i] = (- FIX(0.71414)) * x;
	/* Cb=>G value is scaled-up -0.34414 * x */
	/* We also add in ONE_HALF so that need not do it in inner loop */
	upsample->Cb_g_tab[i] = (- FIX(0.34414)) * x + ONE_HALF;
	}
	}


	/*
	* Initialize for an upsampling pass.
	*/

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

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


	/*
	* Control routine to do upsampling (and color conversion).
	*
	* The control routine just handles the row buffering considerations.
	*/

	METHODDEF(void)
	merged_2v_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)
	/* 2:1 vertical sampling case: may need a spare row. */
	{
	my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
	JSAMPROW work_ptrs[2];
	JDIMENSION num_rows; /* number of rows returned to caller */

	if (upsample->spare_full) {
	/* If we have a spare row saved from a previous cycle, just return it. */
	jcopy_sample_rows(& upsample->spare_row, 0, output_buf + *out_row_ctr, 0,
	1, upsample->out_row_width);
	num_rows = 1;
	upsample->spare_full = FALSE;
	} else {
	/* Figure number of rows to return to caller. */
	num_rows = 2;
	/* Not more than the distance to the end of the image. */
	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;
	/* Create output pointer array for upsampler. */
	work_ptrs[0] = output_buf[*out_row_ctr];
	if (num_rows > 1) {
	work_ptrs[1] = output_buf[*out_row_ctr + 1];
	} else {
	work_ptrs[1] = upsample->spare_row;
	upsample->spare_full = TRUE;
	}
	/* Now do the upsampling. */
	(upsample->upmethod) (cinfo, input_buf, in_row_group_ctr, work_ptrs);
	}

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


	METHODDEF(void)
	merged_1v_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)
	/* 1:1 vertical sampling case: much easier, never need a spare row. */
	{
	my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;

	/* Just do the upsampling. */
	(upsample->upmethod) (cinfo, input_buf, in_row_group_ctr,
	output_buf + *out_row_ctr);
	/* Adjust counts */
	(*out_row_ctr)++;
	(*in_row_group_ctr)++;
	}


	/*
	* These are the routines invoked by the control routines to do
	* the actual upsampling/conversion. One row group is processed per call.
	*
	* Note: since we may be writing directly into application-supplied buffers,
	* we have to be honest about the output width; we can't assume the buffer
	* has been rounded up to an even width.
	*/


	/*
	* Upsample and color convert for the case of 2:1 horizontal and 1:1 vertical.
	*/

	METHODDEF(void)
	h2v1_merged_upsample (j_decompress_ptr cinfo,
	JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr,
	JSAMPARRAY output_buf)
	{
	my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
	register int y, cred, cgreen, cblue;
	int cb, cr;
	register JSAMPROW outptr;
	JSAMPROW inptr0, inptr1, inptr2;
	JDIMENSION col;
	/* copy these pointers into registers if possible */
	register JSAMPLE * range_limit = cinfo->sample_range_limit;
	int * Crrtab = upsample->Cr_r_tab;
	int * Cbbtab = upsample->Cb_b_tab;
	INT32 * Crgtab = upsample->Cr_g_tab;
	INT32 * Cbgtab = upsample->Cb_g_tab;
	SHIFT_TEMPS

	inptr0 = input_buf[0][in_row_group_ctr];
	inptr1 = input_buf[1][in_row_group_ctr];
	inptr2 = input_buf[2][in_row_group_ctr];
	outptr = output_buf[0];
	/* Loop for each pair of output pixels */
	for (col = cinfo->output_width >> 1; col > 0; col--) {
	/* Do the chroma part of the calculation */
	cb = GETJSAMPLE(*inptr1++);
	cr = GETJSAMPLE(*inptr2++);
	cred = Crrtab[cr];
	cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
	cblue = Cbbtab[cb];
	/* Fetch 2 Y values and emit 2 pixels */
	y = GETJSAMPLE(*inptr0++);
	outptr[RGB_RED] = range_limit[y + cred];
	outptr[RGB_GREEN] = range_limit[y + cgreen];
	outptr[RGB_BLUE] = range_limit[y + cblue];
	outptr += RGB_PIXELSIZE;
	y = GETJSAMPLE(*inptr0++);
	outptr[RGB_RED] = range_limit[y + cred];
	outptr[RGB_GREEN] = range_limit[y + cgreen];
	outptr[RGB_BLUE] = range_limit[y + cblue];
	outptr += RGB_PIXELSIZE;
	}
	/* If image width is odd, do the last output column separately */
	if (cinfo->output_width & 1) {
	cb = GETJSAMPLE(*inptr1);
	cr = GETJSAMPLE(*inptr2);
	cred = Crrtab[cr];
	cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
	cblue = Cbbtab[cb];
	y = GETJSAMPLE(*inptr0);
	outptr[RGB_RED] = range_limit[y + cred];
	outptr[RGB_GREEN] = range_limit[y + cgreen];
	outptr[RGB_BLUE] = range_limit[y + cblue];
	}
	}


	/*
	* Upsample and color convert for the case of 2:1 horizontal and 2:1 vertical.
	*/

	METHODDEF(void)
	h2v2_merged_upsample (j_decompress_ptr cinfo,
	JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr,
	JSAMPARRAY output_buf)
	{
	my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
	register int y, cred, cgreen, cblue;
	int cb, cr;
	register JSAMPROW outptr0, outptr1;
	JSAMPROW inptr00, inptr01, inptr1, inptr2;
	JDIMENSION col;
	/* copy these pointers into registers if possible */
	register JSAMPLE * range_limit = cinfo->sample_range_limit;
	int * Crrtab = upsample->Cr_r_tab;
	int * Cbbtab = upsample->Cb_b_tab;
	INT32 * Crgtab = upsample->Cr_g_tab;
	INT32 * Cbgtab = upsample->Cb_g_tab;
	SHIFT_TEMPS

	inptr00 = input_buf[0][in_row_group_ctr*2];
	inptr01 = input_buf[0][in_row_group_ctr*2 + 1];
	inptr1 = input_buf[1][in_row_group_ctr];
	inptr2 = input_buf[2][in_row_group_ctr];
	outptr0 = output_buf[0];
	outptr1 = output_buf[1];
	/* Loop for each group of output pixels */
	for (col = cinfo->output_width >> 1; col > 0; col--) {
	/* Do the chroma part of the calculation */
	cb = GETJSAMPLE(*inptr1++);
	cr = GETJSAMPLE(*inptr2++);
	cred = Crrtab[cr];
	cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
	cblue = Cbbtab[cb];
	/* Fetch 4 Y values and emit 4 pixels */
	y = GETJSAMPLE(*inptr00++);
	outptr0[RGB_RED] = range_limit[y + cred];
	outptr0[RGB_GREEN] = range_limit[y + cgreen];
	outptr0[RGB_BLUE] = range_limit[y + cblue];
	outptr0 += RGB_PIXELSIZE;
	y = GETJSAMPLE(*inptr00++);
	outptr0[RGB_RED] = range_limit[y + cred];
	outptr0[RGB_GREEN] = range_limit[y + cgreen];
	outptr0[RGB_BLUE] = range_limit[y + cblue];
	outptr0 += RGB_PIXELSIZE;
	y = GETJSAMPLE(*inptr01++);
	outptr1[RGB_RED] = range_limit[y + cred];
	outptr1[RGB_GREEN] = range_limit[y + cgreen];
	outptr1[RGB_BLUE] = range_limit[y + cblue];
	outptr1 += RGB_PIXELSIZE;
	y = GETJSAMPLE(*inptr01++);
	outptr1[RGB_RED] = range_limit[y + cred];
	outptr1[RGB_GREEN] = range_limit[y + cgreen];
	outptr1[RGB_BLUE] = range_limit[y + cblue];
	outptr1 += RGB_PIXELSIZE;
	}
	/* If image width is odd, do the last output column separately */
	if (cinfo->output_width & 1) {
	cb = GETJSAMPLE(*inptr1);
	cr = GETJSAMPLE(*inptr2);
	cred = Crrtab[cr];
	cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
	cblue = Cbbtab[cb];
	y = GETJSAMPLE(*inptr00);
	outptr0[RGB_RED] = range_limit[y + cred];
	outptr0[RGB_GREEN] = range_limit[y + cgreen];
	outptr0[RGB_BLUE] = range_limit[y + cblue];
	y = GETJSAMPLE(*inptr01);
	outptr1[RGB_RED] = range_limit[y + cred];
	outptr1[RGB_GREEN] = range_limit[y + cgreen];
	outptr1[RGB_BLUE] = range_limit[y + cblue];
	}
	}


	/*
	* Module initialization routine for merged upsampling/color conversion.
	*
	* NB: this is called under the conditions determined by use_merged_upsample()
	* in jdmaster.c. That routine MUST correspond to the actual capabilities
	* of this module; no safety checks are made here.
	*/

	GLOBAL(void)
	jinit_merged_upsampler (j_decompress_ptr cinfo)
	{
	my_upsample_ptr upsample;

	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_merged_upsample;
	upsample->pub.need_context_rows = FALSE;

	upsample->out_row_width = cinfo->output_width * cinfo->out_color_components;

	if (cinfo->max_v_samp_factor == 2) {
	upsample->pub.upsample = merged_2v_upsample;
	upsample->upmethod = h2v2_merged_upsample;
	/* Allocate a spare row buffer */
	upsample->spare_row = (JSAMPROW)
	(*cinfo->mem->alloc_large) ((j_common_ptr) cinfo, JPOOL_IMAGE,
	(size_t) (upsample->out_row_width * SIZEOF(JSAMPLE)));
	} else {
	upsample->pub.upsample = merged_1v_upsample;
	upsample->upmethod = h2v1_merged_upsample;
	/* No spare row needed */
	upsample->spare_row = NULL;
	}

	build_ycc_rgb_table(cinfo);
	}

	#endif /* UPSAMPLE_MERGING_SUPPORTED */