/* * jccolor.c * * This file was part of the Independent JPEG Group's software: * Copyright (C) 1991-1996, Thomas G. Lane. * libjpeg-turbo Modifications: * Copyright 2009 Pierre Ossman <[email protected]> for Cendio AB * Copyright (C) 2009-2012, 2015, 2022, D. R. Commander. * Copyright (C) 2014, MIPS Technologies, Inc., California. * For conditions of distribution and use, see the accompanying README.ijg * file. * * This file contains input colorspace conversion routines. */ #define JPEG_INTERNALS #include "jinclude.h" #include "jpeglib.h" #include "jsimd.h" /* Private subobject */ my_color_converter; my_cconvert_ptr; /**************** RGB -> YCbCr conversion: most common case **************/ /* * YCbCr is defined per CCIR 601-1, except that Cb and Cr are * normalized to the range 0..MAXJSAMPLE rather than -0.5 .. 0.5. * The conversion equations to be implemented are therefore * Y = 0.29900 * R + 0.58700 * G + 0.11400 * B * Cb = -0.16874 * R - 0.33126 * G + 0.50000 * B + CENTERJSAMPLE * Cr = 0.50000 * R - 0.41869 * G - 0.08131 * B + CENTERJSAMPLE * (These numbers are derived from TIFF 6.0 section 21, dated 3-June-92.) * 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 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 … #define CBCR_OFFSET … #define ONE_HALF … #define FIX(x) … /* 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 … #define G_Y_OFF … #define B_Y_OFF … #define R_CB_OFF … #define G_CB_OFF … #define B_CB_OFF … #define R_CR_OFF … #define G_CR_OFF … #define B_CR_OFF … #define TABLE_SIZE … /* 12-bit samples use a 16-bit data type, so it is possible to pass * out-of-range sample values (< 0 or > 4095) to jpeg_write_scanlines(). * Thus, we mask the incoming 12-bit samples to guard against overrunning * or underrunning the conversion tables. */ #if BITS_IN_JSAMPLE == 12 #define RANGE_LIMIT … #else #define RANGE_LIMIT(value) … #endif /* Include inline routines for colorspace extensions */ #include "jccolext.c" #undef RGB_RED #undef RGB_GREEN #undef RGB_BLUE #undef RGB_PIXELSIZE #define RGB_RED … #define RGB_GREEN … #define RGB_BLUE … #define RGB_PIXELSIZE … #define rgb_ycc_convert_internal … #define rgb_gray_convert_internal … #define rgb_rgb_convert_internal … #include "jccolext.c" #undef RGB_RED #undef RGB_GREEN #undef RGB_BLUE #undef RGB_PIXELSIZE #undef rgb_ycc_convert_internal #undef rgb_gray_convert_internal #undef rgb_rgb_convert_internal #define RGB_RED … #define RGB_GREEN … #define RGB_BLUE … #define RGB_PIXELSIZE … #define rgb_ycc_convert_internal … #define rgb_gray_convert_internal … #define rgb_rgb_convert_internal … #include "jccolext.c" #undef RGB_RED #undef RGB_GREEN #undef RGB_BLUE #undef RGB_PIXELSIZE #undef rgb_ycc_convert_internal #undef rgb_gray_convert_internal #undef rgb_rgb_convert_internal #define RGB_RED … #define RGB_GREEN … #define RGB_BLUE … #define RGB_PIXELSIZE … #define rgb_ycc_convert_internal … #define rgb_gray_convert_internal … #define rgb_rgb_convert_internal … #include "jccolext.c" #undef RGB_RED #undef RGB_GREEN #undef RGB_BLUE #undef RGB_PIXELSIZE #undef rgb_ycc_convert_internal #undef rgb_gray_convert_internal #undef rgb_rgb_convert_internal #define RGB_RED … #define RGB_GREEN … #define RGB_BLUE … #define RGB_PIXELSIZE … #define rgb_ycc_convert_internal … #define rgb_gray_convert_internal … #define rgb_rgb_convert_internal … #include "jccolext.c" #undef RGB_RED #undef RGB_GREEN #undef RGB_BLUE #undef RGB_PIXELSIZE #undef rgb_ycc_convert_internal #undef rgb_gray_convert_internal #undef rgb_rgb_convert_internal #define RGB_RED … #define RGB_GREEN … #define RGB_BLUE … #define RGB_PIXELSIZE … #define rgb_ycc_convert_internal … #define rgb_gray_convert_internal … #define rgb_rgb_convert_internal … #include "jccolext.c" #undef RGB_RED #undef RGB_GREEN #undef RGB_BLUE #undef RGB_PIXELSIZE #undef rgb_ycc_convert_internal #undef rgb_gray_convert_internal #undef rgb_rgb_convert_internal #define RGB_RED … #define RGB_GREEN … #define RGB_BLUE … #define RGB_PIXELSIZE … #define rgb_ycc_convert_internal … #define rgb_gray_convert_internal … #define rgb_rgb_convert_internal … #include "jccolext.c" #undef RGB_RED #undef RGB_GREEN #undef RGB_BLUE #undef RGB_PIXELSIZE #undef rgb_ycc_convert_internal #undef rgb_gray_convert_internal #undef rgb_rgb_convert_internal /* * Initialize for RGB->YCC colorspace conversion. */ METHODDEF(void) rgb_ycc_start(j_compress_ptr cinfo) { … } /* * Convert some rows of samples to the JPEG colorspace. */ METHODDEF(void) rgb_ycc_convert(j_compress_ptr cinfo, JSAMPARRAY input_buf, JSAMPIMAGE output_buf, JDIMENSION output_row, int num_rows) { … } /**************** Cases other than RGB -> YCbCr **************/ /* * Convert some rows of samples to the JPEG colorspace. */ METHODDEF(void) rgb_gray_convert(j_compress_ptr cinfo, JSAMPARRAY input_buf, JSAMPIMAGE output_buf, JDIMENSION output_row, int num_rows) { … } /* * Extended RGB to plain RGB conversion */ METHODDEF(void) rgb_rgb_convert(j_compress_ptr cinfo, JSAMPARRAY input_buf, JSAMPIMAGE output_buf, JDIMENSION output_row, int num_rows) { … } /* * 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) { … } /* * 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 YCbCr (since Y == gray). */ METHODDEF(void) grayscale_convert(j_compress_ptr cinfo, JSAMPARRAY input_buf, JSAMPIMAGE output_buf, JDIMENSION output_row, int num_rows) { … } /* * 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) { … } /* * Empty method for start_pass. */ METHODDEF(void) null_method(j_compress_ptr cinfo) { … } /* * Module initialization routine for input colorspace conversion. */ GLOBAL(void) jinit_color_converter(j_compress_ptr cinfo) { … }
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