ref: 2c23de27d5006e969106fad672399fafe6464845
dir: /DoConfig/fltk/jpeg/jccolor.c/
/* * jccolor.c * * Copyright (C) 1991-1996, Thomas G. Lane. * Modified 2011-2013 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. * * This file contains input colorspace conversion routines. */ #define JPEG_INTERNALS #include "jinclude.h" #include "jpeglib.h" /* Private subobject */ typedef struct { struct jpeg_color_converter pub; /* public fields */ /* Private state for RGB->YCC conversion */ INT32 * rgb_ycc_tab; /* => table for RGB to YCbCr conversion */ } my_color_converter; typedef my_color_converter * my_cconvert_ptr; /**************** RGB -> YCbCr conversion: most common case **************/ /* * YCbCr is defined per Recommendation ITU-R BT.601-7 (03/2011), * previously known as Recommendation CCIR 601-1, except that Cb and Cr * are normalized to the range 0..MAXJSAMPLE rather than -0.5 .. 0.5. * sRGB (standard RGB color space) is defined per IEC 61966-2-1:1999. * sYCC (standard luma-chroma-chroma color space with extended gamut) * is defined per IEC 61966-2-1:1999 Amendment A1:2003 Annex F. * bg-sRGB and bg-sYCC (big gamut standard color spaces) * are defined per IEC 61966-2-1:1999 Amendment A1:2003 Annex G. * 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) * 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), * 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 * Cr = 0.5 * R - 0.418687589 * G - 0.081312411 * B + CENTERJSAMPLE * Note: older versions of the IJG code used a zero offset of MAXJSAMPLE/2, * rather than CENTERJSAMPLE, for Cb and Cr. This gave equal positive and * negative swings for Cb/Cr, but meant that grayscale values (Cb=Cr=0) * were not represented exactly. Now we sacrifice exact representation of * maximum red and maximum blue in order to get exact grayscales. * * To avoid floating-point arithmetic, we represent the fractional constants * as integers scaled up by 2^16 (about 4 digits precision); we have to divide * the products by 2^16, with appropriate rounding, to get the correct answer. * * For even more speed, we avoid doing any multiplications in the inner loop * 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. * 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. */ #define SCALEBITS 16 /* speediest right-shift on some machines */ #define CBCR_OFFSET ((INT32) CENTERJSAMPLE << SCALEBITS) #define ONE_HALF ((INT32) 1 << (SCALEBITS-1)) #define FIX(x) ((INT32) ((x) * (1L<<SCALEBITS) + 0.5)) /* We allocate one big table and divide it up into eight parts, instead of * doing eight alloc_small requests. This lets us use a single table base * address, which can be held in a register in the inner loops on many * machines (more than can hold all eight addresses, anyway). */ #define R_Y_OFF 0 /* offset to R => Y section */ #define G_Y_OFF (1*(MAXJSAMPLE+1)) /* offset to G => Y section */ #define B_Y_OFF (2*(MAXJSAMPLE+1)) /* etc. */ #define R_CB_OFF (3*(MAXJSAMPLE+1)) #define G_CB_OFF (4*(MAXJSAMPLE+1)) #define B_CB_OFF (5*(MAXJSAMPLE+1)) #define R_CR_OFF B_CB_OFF /* B=>Cb, R=>Cr are the same */ #define G_CR_OFF (6*(MAXJSAMPLE+1)) #define B_CR_OFF (7*(MAXJSAMPLE+1)) #define TABLE_SIZE (8*(MAXJSAMPLE+1)) /* * Initialize for RGB->YCC colorspace conversion. */ METHODDEF(void) rgb_ycc_start (j_compress_ptr cinfo) { my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert; INT32 * rgb_ycc_tab; INT32 i; /* Allocate and fill in the conversion tables. */ cconvert->rgb_ycc_tab = rgb_ycc_tab = (INT32 *) (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, (TABLE_SIZE * SIZEOF(INT32))); 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+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; /* 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+G_CR_OFF] = (-FIX(0.418687589)) * i; rgb_ycc_tab[i+B_CR_OFF] = (-FIX(0.081312411)) * i; } } /* * Convert some rows of samples to the JPEG colorspace. * * Note that we change from the application's interleaved-pixel format * to our internal noninterleaved, one-plane-per-component format. * The input buffer is therefore three times as wide as the output buffer. * * A starting row offset is provided only for the output buffer. The caller * can easily adjust the passed input_buf value to accommodate any row * offset required on that side. */ METHODDEF(void) rgb_ycc_convert (j_compress_ptr cinfo, JSAMPARRAY input_buf, JSAMPIMAGE output_buf, JDIMENSION output_row, int num_rows) { my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert; register INT32 * ctab = cconvert->rgb_ycc_tab; register int r, g, b; register JSAMPROW inptr; register JSAMPROW outptr0, outptr1, outptr2; register JDIMENSION col; JDIMENSION num_cols = cinfo->image_width; while (--num_rows >= 0) { inptr = *input_buf++; outptr0 = output_buf[0][output_row]; outptr1 = output_buf[1][output_row]; outptr2 = output_buf[2][output_row]; output_row++; for (col = 0; col < num_cols; col++) { r = GETJSAMPLE(inptr[RGB_RED]); g = GETJSAMPLE(inptr[RGB_GREEN]); b = GETJSAMPLE(inptr[RGB_BLUE]); /* If the inputs are 0..MAXJSAMPLE, the outputs of these equations * must be too; we do not need an explicit range-limiting operation. * Hence the value being shifted is never negative, and we don't * need the general RIGHT_SHIFT macro. */ /* Y */ outptr0[col] = (JSAMPLE) ((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF]) >> SCALEBITS); /* Cb */ outptr1[col] = (JSAMPLE) ((ctab[r+R_CB_OFF] + ctab[g+G_CB_OFF] + ctab[b+B_CB_OFF]) >> SCALEBITS); /* Cr */ outptr2[col] = (JSAMPLE) ((ctab[r+R_CR_OFF] + ctab[g+G_CR_OFF] + ctab[b+B_CR_OFF]) >> SCALEBITS); inptr += RGB_PIXELSIZE; } } } /**************** Cases other than RGB -> YCbCr **************/ /* * 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. * We assume rgb_ycc_start has been called (we only use the Y tables). */ METHODDEF(void) rgb_gray_convert (j_compress_ptr cinfo, JSAMPARRAY input_buf, JSAMPIMAGE output_buf, JDIMENSION output_row, int num_rows) { my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert; register INT32 * ctab = cconvert->rgb_ycc_tab; register int r, g, b; register JSAMPROW inptr; register JSAMPROW outptr; register JDIMENSION col; JDIMENSION num_cols = cinfo->image_width; while (--num_rows >= 0) { 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 */ outptr[col] = (JSAMPLE) ((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF]) >> SCALEBITS); inptr += RGB_PIXELSIZE; } } } /* * Convert some rows of samples to the JPEG colorspace. * This version handles Adobe-style CMYK->YCCK conversion, * where we convert R=1-C, G=1-M, and B=1-Y to YCbCr using the same * conversion as above, while passing K (black) unchanged. * We assume rgb_ycc_start has been called. */ METHODDEF(void) cmyk_ycck_convert (j_compress_ptr cinfo, JSAMPARRAY input_buf, JSAMPIMAGE output_buf, JDIMENSION output_row, int num_rows) { my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert; register INT32 * ctab = cconvert->rgb_ycc_tab; register int r, g, b; register JSAMPROW inptr; register JSAMPROW outptr0, outptr1, outptr2, outptr3; register JDIMENSION col; JDIMENSION num_cols = cinfo->image_width; while (--num_rows >= 0) { inptr = *input_buf++; outptr0 = output_buf[0][output_row]; outptr1 = output_buf[1][output_row]; outptr2 = output_buf[2][output_row]; outptr3 = output_buf[3][output_row]; output_row++; for (col = 0; col < num_cols; col++) { r = MAXJSAMPLE - GETJSAMPLE(inptr[0]); g = MAXJSAMPLE - GETJSAMPLE(inptr[1]); b = MAXJSAMPLE - GETJSAMPLE(inptr[2]); /* K passes through as-is */ outptr3[col] = inptr[3]; /* don't need GETJSAMPLE here */ /* If the inputs are 0..MAXJSAMPLE, the outputs of these equations * must be too; we do not need an explicit range-limiting operation. * Hence the value being shifted is never negative, and we don't * need the general RIGHT_SHIFT macro. */ /* Y */ outptr0[col] = (JSAMPLE) ((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF]) >> SCALEBITS); /* Cb */ outptr1[col] = (JSAMPLE) ((ctab[r+R_CB_OFF] + ctab[g+G_CB_OFF] + ctab[b+B_CB_OFF]) >> SCALEBITS); /* Cr */ outptr2[col] = (JSAMPLE) ((ctab[r+R_CR_OFF] + ctab[g+G_CR_OFF] + ctab[b+B_CR_OFF]) >> SCALEBITS); inptr += 4; } } } /* * Convert some rows of samples to the JPEG colorspace. * [R,G,B] to [R-G,G,B-G] conversion with modulo calculation * (forward reversible color transform). * This can be seen as an adaption of the general RGB->YCbCr * conversion equation with Kr = Kb = 0, while replacing the * normalization by modulo calculation. */ METHODDEF(void) rgb_rgb1_convert (j_compress_ptr cinfo, JSAMPARRAY input_buf, JSAMPIMAGE output_buf, JDIMENSION output_row, int num_rows) { register int r, g, b; register JSAMPROW inptr; register JSAMPROW outptr0, outptr1, outptr2; register JDIMENSION col; JDIMENSION num_cols = cinfo->image_width; while (--num_rows >= 0) { inptr = *input_buf++; outptr0 = output_buf[0][output_row]; outptr1 = output_buf[1][output_row]; outptr2 = output_buf[2][output_row]; output_row++; for (col = 0; col < num_cols; col++) { r = GETJSAMPLE(inptr[RGB_RED]); g = GETJSAMPLE(inptr[RGB_GREEN]); b = GETJSAMPLE(inptr[RGB_BLUE]); /* Assume that MAXJSAMPLE+1 is a power of 2, so that the MOD * (modulo) operator is equivalent to the bitmask operator AND. */ outptr0[col] = (JSAMPLE) ((r - g + CENTERJSAMPLE) & MAXJSAMPLE); outptr1[col] = (JSAMPLE) g; outptr2[col] = (JSAMPLE) ((b - g + CENTERJSAMPLE) & MAXJSAMPLE); inptr += RGB_PIXELSIZE; } } } /* * Convert some rows of samples to the JPEG colorspace. * This version handles grayscale output with no conversion. * The source can be either plain grayscale or YCC (since Y == gray). */ METHODDEF(void) grayscale_convert (j_compress_ptr cinfo, JSAMPARRAY input_buf, JSAMPIMAGE output_buf, JDIMENSION output_row, int num_rows) { int instride = cinfo->input_components; register JSAMPROW inptr; register JSAMPROW outptr; register JDIMENSION col; JDIMENSION num_cols = cinfo->image_width; while (--num_rows >= 0) { inptr = *input_buf++; outptr = output_buf[0][output_row++]; for (col = 0; col < num_cols; col++) { outptr[col] = inptr[0]; /* don't need GETJSAMPLE() here */ inptr += instride; } } } /* * Convert some rows of samples to the JPEG colorspace. * No colorspace conversion, but change from interleaved * to separate-planes representation. */ METHODDEF(void) rgb_convert (j_compress_ptr cinfo, JSAMPARRAY input_buf, JSAMPIMAGE output_buf, JDIMENSION output_row, int num_rows) { register JSAMPROW inptr; register JSAMPROW outptr0, outptr1, outptr2; register JDIMENSION col; JDIMENSION num_cols = cinfo->image_width; while (--num_rows >= 0) { inptr = *input_buf++; outptr0 = output_buf[0][output_row]; outptr1 = output_buf[1][output_row]; outptr2 = output_buf[2][output_row]; output_row++; for (col = 0; col < num_cols; col++) { /* We can dispense with GETJSAMPLE() here */ outptr0[col] = inptr[RGB_RED]; outptr1[col] = inptr[RGB_GREEN]; outptr2[col] = inptr[RGB_BLUE]; inptr += RGB_PIXELSIZE; } } } /* * Convert some rows of samples to the JPEG colorspace. * This version handles multi-component colorspaces without conversion. * We assume input_components == num_components. */ METHODDEF(void) null_convert (j_compress_ptr cinfo, JSAMPARRAY input_buf, JSAMPIMAGE output_buf, JDIMENSION output_row, int num_rows) { int ci; register int nc = cinfo->num_components; register JSAMPROW inptr; register JSAMPROW outptr; register JDIMENSION col; JDIMENSION num_cols = cinfo->image_width; while (--num_rows >= 0) { /* It seems fastest to make a separate pass for each component. */ for (ci = 0; ci < nc; ci++) { inptr = input_buf[0] + ci; outptr = output_buf[ci][output_row]; for (col = 0; col < num_cols; col++) { *outptr++ = *inptr; /* don't need GETJSAMPLE() here */ inptr += nc; } } input_buf++; output_row++; } } /* * Empty method for start_pass. */ METHODDEF(void) null_method (j_compress_ptr cinfo) { /* no work needed */ } /* * Module initialization routine for input colorspace conversion. */ GLOBAL(void) jinit_color_converter (j_compress_ptr cinfo) { my_cconvert_ptr cconvert; cconvert = (my_cconvert_ptr) (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, SIZEOF(my_color_converter)); cinfo->cconvert = &cconvert->pub; /* set start_pass to null method until we find out differently */ cconvert->pub.start_pass = null_method; /* Make sure input_components agrees with in_color_space */ switch (cinfo->in_color_space) { case JCS_GRAYSCALE: if (cinfo->input_components != 1) ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE); break; case JCS_RGB: case JCS_BG_RGB: if (cinfo->input_components != RGB_PIXELSIZE) ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE); break; case JCS_YCbCr: case JCS_BG_YCC: if (cinfo->input_components != 3) ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE); break; case JCS_CMYK: case JCS_YCCK: if (cinfo->input_components != 4) ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE); break; default: /* JCS_UNKNOWN can be anything */ if (cinfo->input_components < 1) ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE); break; } /* Support color transform only for RGB colorspaces */ if (cinfo->color_transform && cinfo->jpeg_color_space != JCS_RGB && cinfo->jpeg_color_space != JCS_BG_RGB) ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); /* Check num_components, set conversion method based on requested space */ switch (cinfo->jpeg_color_space) { case JCS_GRAYSCALE: if (cinfo->num_components != 1) ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); switch (cinfo->in_color_space) { case JCS_GRAYSCALE: case JCS_YCbCr: case JCS_BG_YCC: cconvert->pub.color_convert = grayscale_convert; break; case JCS_RGB: cconvert->pub.start_pass = rgb_ycc_start; cconvert->pub.color_convert = rgb_gray_convert; break; default: ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); } break; case JCS_RGB: case JCS_BG_RGB: if (cinfo->num_components != 3) ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); if (cinfo->in_color_space == cinfo->jpeg_color_space) { switch (cinfo->color_transform) { case JCT_NONE: cconvert->pub.color_convert = rgb_convert; break; case JCT_SUBTRACT_GREEN: cconvert->pub.color_convert = rgb_rgb1_convert; break; default: ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); } } else ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); break; case JCS_YCbCr: if (cinfo->num_components != 3) ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); switch (cinfo->in_color_space) { case JCS_RGB: cconvert->pub.start_pass = rgb_ycc_start; cconvert->pub.color_convert = rgb_ycc_convert; break; case JCS_YCbCr: cconvert->pub.color_convert = null_convert; break; default: ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); } break; case JCS_BG_YCC: if (cinfo->num_components != 3) ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); switch (cinfo->in_color_space) { case JCS_RGB: /* For conversion from normal RGB input to BG_YCC representation, * the Cb/Cr values are first computed as usual, and then * quantized further after DCT processing by a factor of * 2 in reference to the nominal quantization factor. */ /* need quantization scale by factor of 2 after DCT */ cinfo->comp_info[1].component_needed = TRUE; cinfo->comp_info[2].component_needed = TRUE; /* compute normal YCC first */ cconvert->pub.start_pass = rgb_ycc_start; cconvert->pub.color_convert = rgb_ycc_convert; break; case JCS_YCbCr: /* need quantization scale by factor of 2 after DCT */ cinfo->comp_info[1].component_needed = TRUE; cinfo->comp_info[2].component_needed = TRUE; /*FALLTHROUGH*/ case JCS_BG_YCC: /* Pass through for BG_YCC input */ cconvert->pub.color_convert = null_convert; break; default: ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); } break; case JCS_CMYK: if (cinfo->num_components != 4) ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); if (cinfo->in_color_space == JCS_CMYK) cconvert->pub.color_convert = null_convert; else ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); break; case JCS_YCCK: if (cinfo->num_components != 4) ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); switch (cinfo->in_color_space) { case JCS_CMYK: cconvert->pub.start_pass = rgb_ycc_start; cconvert->pub.color_convert = cmyk_ycck_convert; break; case JCS_YCCK: cconvert->pub.color_convert = null_convert; break; default: ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); } break; default: /* allow null conversion of JCS_UNKNOWN */ if (cinfo->jpeg_color_space != cinfo->in_color_space || cinfo->num_components != cinfo->input_components) ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); cconvert->pub.color_convert = null_convert; break; } }