diff options
Diffstat (limited to 'jpeg/jccolor.c')
| -rw-r--r-- | jpeg/jccolor.c | 35 |
1 files changed, 16 insertions, 19 deletions
diff --git a/jpeg/jccolor.c b/jpeg/jccolor.c index db2ca429e..c028dd9db 100644 --- a/jpeg/jccolor.c +++ b/jpeg/jccolor.c @@ -2,7 +2,7 @@ * jccolor.c * * Copyright (C) 1991-1996, Thomas G. Lane. - * Modified 2011-2019 by Guido Vollbeding. + * Modified 2011-2023 by Guido Vollbeding. * This file is part of the Independent JPEG Group's software. * For conditions of distribution and use, see the accompanying README file. * @@ -40,10 +40,10 @@ typedef my_color_converter * my_cconvert_ptr; * Note that the derived conversion coefficients given in some of these * documents are imprecise. The general conversion equations are * Y = Kr * R + (1 - Kr - Kb) * G + Kb * B - * Cb = 0.5 * (B - Y) / (1 - Kb) - * Cr = 0.5 * (R - Y) / (1 - Kr) + * Cb = (B - Y) / (1 - Kb) / K + * Cr = (R - Y) / (1 - Kr) / K * With Kr = 0.299 and Kb = 0.114 (derived according to SMPTE RP 177-1993 - * from the 1953 FCC NTSC primaries and CIE Illuminant C), + * from the 1953 FCC NTSC primaries and CIE Illuminant C), K = 2 for sYCC, * the conversion equations to be implemented are therefore * Y = 0.299 * R + 0.587 * G + 0.114 * B * Cb = -0.168735892 * R - 0.331264108 * G + 0.5 * B + CENTERJSAMPLE @@ -62,8 +62,8 @@ typedef my_color_converter * my_cconvert_ptr; * by precalculating the constants times R,G,B for all possible values. * For 8-bit JSAMPLEs this is very reasonable (only 256 entries per table); * for 9-bit to 12-bit samples it is still acceptable. It's not very - * reasonable for 16-bit samples, but if you want lossless storage you - * shouldn't be changing colorspace anyway. + * reasonable for 16-bit samples, but if you want lossless storage + * you shouldn't be changing colorspace anyway. * The CENTERJSAMPLE offsets and the rounding fudge-factor of 0.5 are included * in the tables to save adding them separately in the inner loop. */ @@ -110,16 +110,16 @@ rgb_ycc_start (j_compress_ptr cinfo) for (i = 0; i <= MAXJSAMPLE; i++) { rgb_ycc_tab[i+R_Y_OFF] = FIX(0.299) * i; rgb_ycc_tab[i+G_Y_OFF] = FIX(0.587) * i; - rgb_ycc_tab[i+B_Y_OFF] = FIX(0.114) * i + ONE_HALF; + rgb_ycc_tab[i+B_Y_OFF] = FIX(0.114) * i + ONE_HALF; rgb_ycc_tab[i+R_CB_OFF] = (- FIX(0.168735892)) * i; rgb_ycc_tab[i+G_CB_OFF] = (- FIX(0.331264108)) * i; /* We use a rounding fudge-factor of 0.5-epsilon for Cb and Cr. * This ensures that the maximum output will round to MAXJSAMPLE * not MAXJSAMPLE+1, and thus that we don't have to range-limit. */ - rgb_ycc_tab[i+B_CB_OFF] = FIX(0.5) * i + CBCR_OFFSET + ONE_HALF-1; + rgb_ycc_tab[i+B_CB_OFF] = (i << (SCALEBITS-1)) + CBCR_OFFSET + ONE_HALF-1; /* B=>Cb and R=>Cr tables are the same - rgb_ycc_tab[i+R_CR_OFF] = FIX(0.5) * i + CBCR_OFFSET + ONE_HALF-1; + rgb_ycc_tab[i+R_CR_OFF] = (i << (SCALEBITS-1)) + CBCR_OFFSET + ONE_HALF-1; */ rgb_ycc_tab[i+G_CR_OFF] = (- FIX(0.418687589)) * i; rgb_ycc_tab[i+B_CR_OFF] = (- FIX(0.081312411)) * i; @@ -190,8 +190,8 @@ rgb_ycc_convert (j_compress_ptr cinfo, /* * Convert some rows of samples to the JPEG colorspace. - * This version handles RGB->grayscale conversion, which is the same - * as the RGB->Y portion of RGB->YCbCr. + * This version handles RGB->grayscale conversion, + * which is the same as the RGB->Y portion of RGB->YCbCr. * We assume rgb_ycc_start has been called (we only use the Y tables). */ @@ -201,7 +201,7 @@ rgb_gray_convert (j_compress_ptr cinfo, JDIMENSION output_row, int num_rows) { my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert; - register int r, g, b; + register INT32 y; register INT32 * ctab = cconvert->rgb_ycc_tab; register JSAMPROW inptr; register JSAMPROW outptr; @@ -212,14 +212,11 @@ rgb_gray_convert (j_compress_ptr cinfo, inptr = *input_buf++; outptr = output_buf[0][output_row++]; for (col = 0; col < num_cols; col++) { - r = GETJSAMPLE(inptr[RGB_RED]); - g = GETJSAMPLE(inptr[RGB_GREEN]); - b = GETJSAMPLE(inptr[RGB_BLUE]); + y = ctab[R_Y_OFF + GETJSAMPLE(inptr[RGB_RED])]; + y += ctab[G_Y_OFF + GETJSAMPLE(inptr[RGB_GREEN])]; + y += ctab[B_Y_OFF + GETJSAMPLE(inptr[RGB_BLUE])]; inptr += RGB_PIXELSIZE; - /* Y */ - outptr[col] = (JSAMPLE) - ((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF]) - >> SCALEBITS); + outptr[col] = (JSAMPLE) (y >> SCALEBITS); } } } |