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Use integer arithmetic for CMYK-to-RGB conversions

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This commit is contained in:
DRC
2011-08-16 01:39:05 +00:00
parent dbb92f2eee
commit 6070e60924
1 changed files with 18 additions and 17 deletions
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35
jdcolor.c
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@@ -115,7 +115,7 @@ cmyk_rgb_convert (j_decompress_ptr cinfo,
JSAMPIMAGE input_buf, JDIMENSION input_row, JSAMPIMAGE input_buf, JDIMENSION input_row,
JSAMPARRAY output_buf, int num_rows) JSAMPARRAY output_buf, int num_rows)
{ {
double cyan, magenta, yellow, black; JSAMPLE cyan, magenta, yellow, black;
register JSAMPROW outptr; register JSAMPROW outptr;
register JSAMPROW inptr0, inptr1, inptr2, inptr3; register JSAMPROW inptr0, inptr1, inptr2, inptr3;
register JDIMENSION col; register JDIMENSION col;
@@ -133,14 +133,14 @@ cmyk_rgb_convert (j_decompress_ptr cinfo,
input_row++; input_row++;
outptr = *output_buf++; outptr = *output_buf++;
for (col = 0; col < num_cols; col++) { for (col = 0; col < num_cols; col++) {
cyan = (double) GETJSAMPLE(inptr0[col]); cyan = GETJSAMPLE(inptr0[col]);
magenta = (double) GETJSAMPLE(inptr1[col]); magenta = GETJSAMPLE(inptr1[col]);
yellow = (double) GETJSAMPLE(inptr2[col]); yellow = GETJSAMPLE(inptr2[col]);
black = (double) GETJSAMPLE(inptr3[col]); black = GETJSAMPLE(inptr3[col]);
outptr[rindex] = (JSAMPLE)(cyan * black / (double)MAXJSAMPLE); outptr[rindex] = (JSAMPLE)((int)cyan * (int)black / MAXJSAMPLE);
outptr[gindex] = (JSAMPLE)(magenta * black / (double)MAXJSAMPLE); outptr[gindex] = (JSAMPLE)((int)magenta * (int)black / MAXJSAMPLE);
outptr[bindex] = (JSAMPLE)(yellow * black / (double)MAXJSAMPLE); outptr[bindex] = (JSAMPLE)((int)yellow * (int)black / MAXJSAMPLE);
outptr += rgbstride; outptr += rgbstride;
} }
} }
@@ -155,7 +155,7 @@ ycck_rgb_convert (j_decompress_ptr cinfo,
JSAMPARRAY output_buf, int num_rows) JSAMPARRAY output_buf, int num_rows)
{ {
my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert; my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
double cyan, magenta, yellow, black; JSAMPLE cyan, magenta, yellow, black;
register int y, cb, cr; register int y, cb, cr;
register JSAMPROW outptr; register JSAMPROW outptr;
register JSAMPROW inptr0, inptr1, inptr2, inptr3; register JSAMPROW inptr0, inptr1, inptr2, inptr3;
@@ -187,19 +187,20 @@ ycck_rgb_convert (j_decompress_ptr cinfo,
y = GETJSAMPLE(inptr0[col]); y = GETJSAMPLE(inptr0[col]);
cb = GETJSAMPLE(inptr1[col]); cb = GETJSAMPLE(inptr1[col]);
cr = GETJSAMPLE(inptr2[col]); cr = GETJSAMPLE(inptr2[col]);
black = (double)GETJSAMPLE(inptr3[col]); black = GETJSAMPLE(inptr3[col]);
/********* Convert YCCK to CMYK **********/ /********* Convert YCCK to CMYK **********/
/* Range-limiting is essential due to noise introduced by DCT losses. */ /* Range-limiting is essential due to noise introduced by DCT losses. */
cyan = (double)range_limit[MAXJSAMPLE - (y + Crrtab[cr])]; cyan = range_limit[MAXJSAMPLE - (y + Crrtab[cr])];
magenta = (double)range_limit[MAXJSAMPLE - magenta = range_limit[MAXJSAMPLE - (y +
(y + ((int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS)))]; ((int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr],
yellow = (double)range_limit[MAXJSAMPLE - (y + Cbbtab[cb])]; SCALEBITS)))];
yellow = range_limit[MAXJSAMPLE - (y + Cbbtab[cb])];
/********* Convert CMYK to RGB **********/ /********* Convert CMYK to RGB **********/
outptr[rindex] = (JSAMPLE)(cyan * black / (double)MAXJSAMPLE); outptr[rindex] = (JSAMPLE)((int)cyan * (int)black / MAXJSAMPLE);
outptr[gindex] = (JSAMPLE)(magenta * black / (double)MAXJSAMPLE); outptr[gindex] = (JSAMPLE)((int)magenta * (int)black / MAXJSAMPLE);
outptr[bindex] = (JSAMPLE)(yellow * black / (double)MAXJSAMPLE); outptr[bindex] = (JSAMPLE)((int)yellow * (int)black / MAXJSAMPLE);
outptr += rgbstride; outptr += rgbstride;
} }
} }