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The Independent JPEG Group's JPEG software v5a

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This commit is contained in:
Thomas G. Lane
1994-12-07 00:00:00 +00:00
committed by DRC
parent 36a4ccccd3
commit 9ba2f5ed36
37 changed files with 1734 additions and 1032 deletions
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15
jdmerge.c
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@@ -82,7 +82,7 @@ METHODDEF void
start_pass_merged_upsample (j_decompress_ptr cinfo)
{
my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
INT32 i, x2;
INT32 i, x;
SHIFT_TEMPS
/* Mark the spare buffer empty */
@@ -106,21 +106,20 @@ start_pass_merged_upsample (j_decompress_ptr cinfo)
(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
(MAXJSAMPLE+1) * SIZEOF(INT32));
for (i = 0; i <= MAXJSAMPLE; i++) {
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 - MAXJSAMPLE/2 */
x2 = 2*i - MAXJSAMPLE; /* twice x */
/* 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(1.40200/2) * x2 + ONE_HALF, SCALEBITS);
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(1.77200/2) * x2 + ONE_HALF, SCALEBITS);
RIGHT_SHIFT(FIX(1.77200) * x + ONE_HALF, SCALEBITS);
/* Cr=>G value is scaled-up -0.71414 * x */
upsample->Cr_g_tab[i] = (- FIX(0.71414/2)) * x2;
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(0.34414/2)) * x2 + ONE_HALF;
upsample->Cb_g_tab[i] = (- FIX(0.34414)) * x + ONE_HALF;
}
}