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plt-scheme  4.2.1
jdmerge.c
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00001 /*
00002  * jdmerge.c
00003  *
00004  * Copyright (C) 1994-1996, Thomas G. Lane.
00005  * This file is part of the Independent JPEG Group's software.
00006  * For conditions of distribution and use, see the accompanying README file.
00007  *
00008  * This file contains code for merged upsampling/color conversion.
00009  *
00010  * This file combines functions from jdsample.c and jdcolor.c;
00011  * read those files first to understand what's going on.
00012  *
00013  * When the chroma components are to be upsampled by simple replication
00014  * (ie, box filtering), we can save some work in color conversion by
00015  * calculating all the output pixels corresponding to a pair of chroma
00016  * samples at one time.  In the conversion equations
00017  *     R = Y           + K1 * Cr
00018  *     G = Y + K2 * Cb + K3 * Cr
00019  *     B = Y + K4 * Cb
00020  * only the Y term varies among the group of pixels corresponding to a pair
00021  * of chroma samples, so the rest of the terms can be calculated just once.
00022  * At typical sampling ratios, this eliminates half or three-quarters of the
00023  * multiplications needed for color conversion.
00024  *
00025  * This file currently provides implementations for the following cases:
00026  *     YCbCr => RGB color conversion only.
00027  *     Sampling ratios of 2h1v or 2h2v.
00028  *     No scaling needed at upsample time.
00029  *     Corner-aligned (non-CCIR601) sampling alignment.
00030  * Other special cases could be added, but in most applications these are
00031  * the only common cases.  (For uncommon cases we fall back on the more
00032  * general code in jdsample.c and jdcolor.c.)
00033  */
00034 
00035 #define JPEG_INTERNALS
00036 #include "jinclude.h"
00037 #include "jpeglib.h"
00038 
00039 #ifdef UPSAMPLE_MERGING_SUPPORTED
00040 
00041 
00042 /* Private subobject */
00043 
00044 typedef struct {
00045   struct jpeg_upsampler pub;       /* public fields */
00046 
00047   /* Pointer to routine to do actual upsampling/conversion of one row group */
00048   JMETHOD(void, upmethod, (j_decompress_ptr cinfo,
00049                         JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr,
00050                         JSAMPARRAY output_buf));
00051 
00052   /* Private state for YCC->RGB conversion */
00053   int * Cr_r_tab;           /* => table for Cr to R conversion */
00054   int * Cb_b_tab;           /* => table for Cb to B conversion */
00055   INT32 * Cr_g_tab;         /* => table for Cr to G conversion */
00056   INT32 * Cb_g_tab;         /* => table for Cb to G conversion */
00057 
00058   /* For 2:1 vertical sampling, we produce two output rows at a time.
00059    * We need a "spare" row buffer to hold the second output row if the
00060    * application provides just a one-row buffer; we also use the spare
00061    * to discard the dummy last row if the image height is odd.
00062    */
00063   JSAMPROW spare_row;
00064   boolean spare_full;              /* T if spare buffer is occupied */
00065 
00066   JDIMENSION out_row_width; /* samples per output row */
00067   JDIMENSION rows_to_go;    /* counts rows remaining in image */
00068 } my_upsampler;
00069 
00070 typedef my_upsampler * my_upsample_ptr;
00071 
00072 #define SCALEBITS    16     /* speediest right-shift on some machines */
00073 #define ONE_HALF     ((INT32) 1 << (SCALEBITS-1))
00074 #define FIX(x)              ((INT32) ((x) * (1L<<SCALEBITS) + 0.5))
00075 
00076 
00077 /*
00078  * Initialize tables for YCC->RGB colorspace conversion.
00079  * This is taken directly from jdcolor.c; see that file for more info.
00080  */
00081 
00082 LOCAL(void)
00083 build_ycc_rgb_table (j_decompress_ptr cinfo)
00084 {
00085   my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
00086   int i;
00087   INT32 x;
00088   SHIFT_TEMPS
00089 
00090   upsample->Cr_r_tab = (int *)
00091     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
00092                             (MAXJSAMPLE+1) * SIZEOF(int));
00093   upsample->Cb_b_tab = (int *)
00094     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
00095                             (MAXJSAMPLE+1) * SIZEOF(int));
00096   upsample->Cr_g_tab = (INT32 *)
00097     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
00098                             (MAXJSAMPLE+1) * SIZEOF(INT32));
00099   upsample->Cb_g_tab = (INT32 *)
00100     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
00101                             (MAXJSAMPLE+1) * SIZEOF(INT32));
00102 
00103   for (i = 0, x = -CENTERJSAMPLE; i <= MAXJSAMPLE; i++, x++) {
00104     /* i is the actual input pixel value, in the range 0..MAXJSAMPLE */
00105     /* The Cb or Cr value we are thinking of is x = i - CENTERJSAMPLE */
00106     /* Cr=>R value is nearest int to 1.40200 * x */
00107     upsample->Cr_r_tab[i] = (int)
00108                   RIGHT_SHIFT(FIX(1.40200) * x + ONE_HALF, SCALEBITS);
00109     /* Cb=>B value is nearest int to 1.77200 * x */
00110     upsample->Cb_b_tab[i] = (int)
00111                   RIGHT_SHIFT(FIX(1.77200) * x + ONE_HALF, SCALEBITS);
00112     /* Cr=>G value is scaled-up -0.71414 * x */
00113     upsample->Cr_g_tab[i] = (- FIX(0.71414)) * x;
00114     /* Cb=>G value is scaled-up -0.34414 * x */
00115     /* We also add in ONE_HALF so that need not do it in inner loop */
00116     upsample->Cb_g_tab[i] = (- FIX(0.34414)) * x + ONE_HALF;
00117   }
00118 }
00119 
00120 
00121 /*
00122  * Initialize for an upsampling pass.
00123  */
00124 
00125 METHODDEF(void)
00126 start_pass_merged_upsample (j_decompress_ptr cinfo)
00127 {
00128   my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
00129 
00130   /* Mark the spare buffer empty */
00131   upsample->spare_full = FALSE;
00132   /* Initialize total-height counter for detecting bottom of image */
00133   upsample->rows_to_go = cinfo->output_height;
00134 }
00135 
00136 
00137 /*
00138  * Control routine to do upsampling (and color conversion).
00139  *
00140  * The control routine just handles the row buffering considerations.
00141  */
00142 
00143 METHODDEF(void)
00144 merged_2v_upsample (j_decompress_ptr cinfo,
00145                   JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
00146                   JDIMENSION in_row_groups_avail,
00147                   JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
00148                   JDIMENSION out_rows_avail)
00149 /* 2:1 vertical sampling case: may need a spare row. */
00150 {
00151   my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
00152   JSAMPROW work_ptrs[2];
00153   JDIMENSION num_rows;             /* number of rows returned to caller */
00154 
00155   if (upsample->spare_full) {
00156     /* If we have a spare row saved from a previous cycle, just return it. */
00157     jcopy_sample_rows(& upsample->spare_row, 0, output_buf + *out_row_ctr, 0,
00158                     1, upsample->out_row_width);
00159     num_rows = 1;
00160     upsample->spare_full = FALSE;
00161   } else {
00162     /* Figure number of rows to return to caller. */
00163     num_rows = 2;
00164     /* Not more than the distance to the end of the image. */
00165     if (num_rows > upsample->rows_to_go)
00166       num_rows = upsample->rows_to_go;
00167     /* And not more than what the client can accept: */
00168     out_rows_avail -= *out_row_ctr;
00169     if (num_rows > out_rows_avail)
00170       num_rows = out_rows_avail;
00171     /* Create output pointer array for upsampler. */
00172     work_ptrs[0] = output_buf[*out_row_ctr];
00173     if (num_rows > 1) {
00174       work_ptrs[1] = output_buf[*out_row_ctr + 1];
00175     } else {
00176       work_ptrs[1] = upsample->spare_row;
00177       upsample->spare_full = TRUE;
00178     }
00179     /* Now do the upsampling. */
00180     (*upsample->upmethod) (cinfo, input_buf, *in_row_group_ctr, work_ptrs);
00181   }
00182 
00183   /* Adjust counts */
00184   *out_row_ctr += num_rows;
00185   upsample->rows_to_go -= num_rows;
00186   /* When the buffer is emptied, declare this input row group consumed */
00187   if (! upsample->spare_full)
00188     (*in_row_group_ctr)++;
00189 }
00190 
00191 
00192 METHODDEF(void)
00193 merged_1v_upsample (j_decompress_ptr cinfo,
00194                   JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
00195                   JDIMENSION in_row_groups_avail,
00196                   JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
00197                   JDIMENSION out_rows_avail)
00198 /* 1:1 vertical sampling case: much easier, never need a spare row. */
00199 {
00200   my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
00201 
00202   /* Just do the upsampling. */
00203   (*upsample->upmethod) (cinfo, input_buf, *in_row_group_ctr,
00204                       output_buf + *out_row_ctr);
00205   /* Adjust counts */
00206   (*out_row_ctr)++;
00207   (*in_row_group_ctr)++;
00208 }
00209 
00210 
00211 /*
00212  * These are the routines invoked by the control routines to do
00213  * the actual upsampling/conversion.  One row group is processed per call.
00214  *
00215  * Note: since we may be writing directly into application-supplied buffers,
00216  * we have to be honest about the output width; we can't assume the buffer
00217  * has been rounded up to an even width.
00218  */
00219 
00220 
00221 /*
00222  * Upsample and color convert for the case of 2:1 horizontal and 1:1 vertical.
00223  */
00224 
00225 METHODDEF(void)
00226 h2v1_merged_upsample (j_decompress_ptr cinfo,
00227                     JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr,
00228                     JSAMPARRAY output_buf)
00229 {
00230   my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
00231   register int y, cred, cgreen, cblue;
00232   int cb, cr;
00233   register JSAMPROW outptr;
00234   JSAMPROW inptr0, inptr1, inptr2;
00235   JDIMENSION col;
00236   /* copy these pointers into registers if possible */
00237   register JSAMPLE * range_limit = cinfo->sample_range_limit;
00238   int * Crrtab = upsample->Cr_r_tab;
00239   int * Cbbtab = upsample->Cb_b_tab;
00240   INT32 * Crgtab = upsample->Cr_g_tab;
00241   INT32 * Cbgtab = upsample->Cb_g_tab;
00242   SHIFT_TEMPS
00243 
00244   inptr0 = input_buf[0][in_row_group_ctr];
00245   inptr1 = input_buf[1][in_row_group_ctr];
00246   inptr2 = input_buf[2][in_row_group_ctr];
00247   outptr = output_buf[0];
00248   /* Loop for each pair of output pixels */
00249   for (col = cinfo->output_width >> 1; col > 0; col--) {
00250     /* Do the chroma part of the calculation */
00251     cb = GETJSAMPLE(*inptr1++);
00252     cr = GETJSAMPLE(*inptr2++);
00253     cred = Crrtab[cr];
00254     cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
00255     cblue = Cbbtab[cb];
00256     /* Fetch 2 Y values and emit 2 pixels */
00257     y  = GETJSAMPLE(*inptr0++);
00258     outptr[RGB_RED] =   range_limit[y + cred];
00259     outptr[RGB_GREEN] = range_limit[y + cgreen];
00260     outptr[RGB_BLUE] =  range_limit[y + cblue];
00261     outptr += RGB_PIXELSIZE;
00262     y  = GETJSAMPLE(*inptr0++);
00263     outptr[RGB_RED] =   range_limit[y + cred];
00264     outptr[RGB_GREEN] = range_limit[y + cgreen];
00265     outptr[RGB_BLUE] =  range_limit[y + cblue];
00266     outptr += RGB_PIXELSIZE;
00267   }
00268   /* If image width is odd, do the last output column separately */
00269   if (cinfo->output_width & 1) {
00270     cb = GETJSAMPLE(*inptr1);
00271     cr = GETJSAMPLE(*inptr2);
00272     cred = Crrtab[cr];
00273     cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
00274     cblue = Cbbtab[cb];
00275     y  = GETJSAMPLE(*inptr0);
00276     outptr[RGB_RED] =   range_limit[y + cred];
00277     outptr[RGB_GREEN] = range_limit[y + cgreen];
00278     outptr[RGB_BLUE] =  range_limit[y + cblue];
00279   }
00280 }
00281 
00282 
00283 /*
00284  * Upsample and color convert for the case of 2:1 horizontal and 2:1 vertical.
00285  */
00286 
00287 METHODDEF(void)
00288 h2v2_merged_upsample (j_decompress_ptr cinfo,
00289                     JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr,
00290                     JSAMPARRAY output_buf)
00291 {
00292   my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
00293   register int y, cred, cgreen, cblue;
00294   int cb, cr;
00295   register JSAMPROW outptr0, outptr1;
00296   JSAMPROW inptr00, inptr01, inptr1, inptr2;
00297   JDIMENSION col;
00298   /* copy these pointers into registers if possible */
00299   register JSAMPLE * range_limit = cinfo->sample_range_limit;
00300   int * Crrtab = upsample->Cr_r_tab;
00301   int * Cbbtab = upsample->Cb_b_tab;
00302   INT32 * Crgtab = upsample->Cr_g_tab;
00303   INT32 * Cbgtab = upsample->Cb_g_tab;
00304   SHIFT_TEMPS
00305 
00306   inptr00 = input_buf[0][in_row_group_ctr*2];
00307   inptr01 = input_buf[0][in_row_group_ctr*2 + 1];
00308   inptr1 = input_buf[1][in_row_group_ctr];
00309   inptr2 = input_buf[2][in_row_group_ctr];
00310   outptr0 = output_buf[0];
00311   outptr1 = output_buf[1];
00312   /* Loop for each group of output pixels */
00313   for (col = cinfo->output_width >> 1; col > 0; col--) {
00314     /* Do the chroma part of the calculation */
00315     cb = GETJSAMPLE(*inptr1++);
00316     cr = GETJSAMPLE(*inptr2++);
00317     cred = Crrtab[cr];
00318     cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
00319     cblue = Cbbtab[cb];
00320     /* Fetch 4 Y values and emit 4 pixels */
00321     y  = GETJSAMPLE(*inptr00++);
00322     outptr0[RGB_RED] =   range_limit[y + cred];
00323     outptr0[RGB_GREEN] = range_limit[y + cgreen];
00324     outptr0[RGB_BLUE] =  range_limit[y + cblue];
00325     outptr0 += RGB_PIXELSIZE;
00326     y  = GETJSAMPLE(*inptr00++);
00327     outptr0[RGB_RED] =   range_limit[y + cred];
00328     outptr0[RGB_GREEN] = range_limit[y + cgreen];
00329     outptr0[RGB_BLUE] =  range_limit[y + cblue];
00330     outptr0 += RGB_PIXELSIZE;
00331     y  = GETJSAMPLE(*inptr01++);
00332     outptr1[RGB_RED] =   range_limit[y + cred];
00333     outptr1[RGB_GREEN] = range_limit[y + cgreen];
00334     outptr1[RGB_BLUE] =  range_limit[y + cblue];
00335     outptr1 += RGB_PIXELSIZE;
00336     y  = GETJSAMPLE(*inptr01++);
00337     outptr1[RGB_RED] =   range_limit[y + cred];
00338     outptr1[RGB_GREEN] = range_limit[y + cgreen];
00339     outptr1[RGB_BLUE] =  range_limit[y + cblue];
00340     outptr1 += RGB_PIXELSIZE;
00341   }
00342   /* If image width is odd, do the last output column separately */
00343   if (cinfo->output_width & 1) {
00344     cb = GETJSAMPLE(*inptr1);
00345     cr = GETJSAMPLE(*inptr2);
00346     cred = Crrtab[cr];
00347     cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
00348     cblue = Cbbtab[cb];
00349     y  = GETJSAMPLE(*inptr00);
00350     outptr0[RGB_RED] =   range_limit[y + cred];
00351     outptr0[RGB_GREEN] = range_limit[y + cgreen];
00352     outptr0[RGB_BLUE] =  range_limit[y + cblue];
00353     y  = GETJSAMPLE(*inptr01);
00354     outptr1[RGB_RED] =   range_limit[y + cred];
00355     outptr1[RGB_GREEN] = range_limit[y + cgreen];
00356     outptr1[RGB_BLUE] =  range_limit[y + cblue];
00357   }
00358 }
00359 
00360 
00361 /*
00362  * Module initialization routine for merged upsampling/color conversion.
00363  *
00364  * NB: this is called under the conditions determined by use_merged_upsample()
00365  * in jdmaster.c.  That routine MUST correspond to the actual capabilities
00366  * of this module; no safety checks are made here.
00367  */
00368 
00369 GLOBAL(void)
00370 jinit_merged_upsampler (j_decompress_ptr cinfo)
00371 {
00372   my_upsample_ptr upsample;
00373 
00374   upsample = (my_upsample_ptr)
00375     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
00376                             SIZEOF(my_upsampler));
00377   cinfo->upsample = (struct jpeg_upsampler *) upsample;
00378   upsample->pub.start_pass = start_pass_merged_upsample;
00379   upsample->pub.need_context_rows = FALSE;
00380 
00381   upsample->out_row_width = cinfo->output_width * cinfo->out_color_components;
00382 
00383   if (cinfo->max_v_samp_factor == 2) {
00384     upsample->pub.upsample = merged_2v_upsample;
00385     upsample->upmethod = h2v2_merged_upsample;
00386     /* Allocate a spare row buffer */
00387     upsample->spare_row = (JSAMPROW)
00388       (*cinfo->mem->alloc_large) ((j_common_ptr) cinfo, JPOOL_IMAGE,
00389               (size_t) (upsample->out_row_width * SIZEOF(JSAMPLE)));
00390   } else {
00391     upsample->pub.upsample = merged_1v_upsample;
00392     upsample->upmethod = h2v1_merged_upsample;
00393     /* No spare row needed */
00394     upsample->spare_row = NULL;
00395   }
00396 
00397   build_ycc_rgb_table(cinfo);
00398 }
00399 
00400 #endif /* UPSAMPLE_MERGING_SUPPORTED */