| /* |
| * jdcolor.c |
| * |
| * Copyright (C) 1991, 1992, Thomas G. Lane. |
| * 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 output colorspace conversion routines. |
| * These routines are invoked via the methods color_convert |
| * and colorout_init/term. |
| */ |
| |
| #include "jinclude.h" |
| |
| |
| /**************** YCbCr -> RGB 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 |
| * R = Y + 1.40200 * Cr |
| * G = Y - 0.34414 * Cb - 0.71414 * Cr |
| * B = Y + 1.77200 * Cb |
| * where Cb and Cr represent the incoming values less MAXJSAMPLE/2. |
| * (These numbers are derived from TIFF 6.0 section 21, dated 3-June-92.) |
| * |
| * 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. |
| * Notice that Y, being an integral input, does not contribute any fraction |
| * so it need not participate in the rounding. |
| * |
| * For even more speed, we avoid doing any multiplications in the inner loop |
| * by precalculating the constants times Cb and Cr 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 Cr=>R and Cb=>B values can be rounded to integers in advance; the |
| * values for the G calculation are left scaled up, since we must add them |
| * together before rounding. |
| */ |
| |
| #ifdef SIXTEEN_BIT_SAMPLES |
| #define SCALEBITS 14 /* avoid overflow */ |
| #else |
| #define SCALEBITS 16 /* speedier right-shift on some machines */ |
| #endif |
| #define ONE_HALF ((INT32) 1 << (SCALEBITS-1)) |
| #define FIX(x) ((INT32) ((x) * (1L<<SCALEBITS) + 0.5)) |
| |
| static int * Cr_r_tab; /* => table for Cr to R conversion */ |
| static int * Cb_b_tab; /* => table for Cb to B conversion */ |
| static INT32 * Cr_g_tab; /* => table for Cr to G conversion */ |
| static INT32 * Cb_g_tab; /* => table for Cb to G conversion */ |
| |
| |
| /* |
| * Initialize for colorspace conversion. |
| */ |
| |
| METHODDEF void |
| ycc_rgb_init (decompress_info_ptr cinfo) |
| { |
| INT32 i, x2; |
| SHIFT_TEMPS |
| |
| Cr_r_tab = (int *) (*cinfo->emethods->alloc_small) |
| ((MAXJSAMPLE+1) * SIZEOF(int)); |
| Cb_b_tab = (int *) (*cinfo->emethods->alloc_small) |
| ((MAXJSAMPLE+1) * SIZEOF(int)); |
| Cr_g_tab = (INT32 *) (*cinfo->emethods->alloc_small) |
| ((MAXJSAMPLE+1) * SIZEOF(INT32)); |
| Cb_g_tab = (INT32 *) (*cinfo->emethods->alloc_small) |
| ((MAXJSAMPLE+1) * SIZEOF(INT32)); |
| |
| for (i = 0; i <= MAXJSAMPLE; i++) { |
| /* 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 */ |
| /* Cr=>R value is nearest int to 1.40200 * x */ |
| Cr_r_tab[i] = (int) |
| RIGHT_SHIFT(FIX(1.40200/2) * x2 + ONE_HALF, SCALEBITS); |
| /* Cb=>B value is nearest int to 1.77200 * x */ |
| Cb_b_tab[i] = (int) |
| RIGHT_SHIFT(FIX(1.77200/2) * x2 + ONE_HALF, SCALEBITS); |
| /* Cr=>G value is scaled-up -0.71414 * x */ |
| Cr_g_tab[i] = (- FIX(0.71414/2)) * x2; |
| /* Cb=>G value is scaled-up -0.34414 * x */ |
| /* We also add in ONE_HALF so that need not do it in inner loop */ |
| Cb_g_tab[i] = (- FIX(0.34414/2)) * x2 + ONE_HALF; |
| } |
| } |
| |
| |
| /* |
| * Convert some rows of samples to the output colorspace. |
| */ |
| |
| METHODDEF void |
| ycc_rgb_convert (decompress_info_ptr cinfo, int num_rows, long num_cols, |
| JSAMPIMAGE input_data, JSAMPIMAGE output_data) |
| { |
| #ifdef SIXTEEN_BIT_SAMPLES |
| register INT32 y; |
| register UINT16 cb, cr; |
| #else |
| register int y, cb, cr; |
| #endif |
| register JSAMPROW inptr0, inptr1, inptr2; |
| register JSAMPROW outptr0, outptr1, outptr2; |
| register long col; |
| /* copy these pointers into registers if possible */ |
| register JSAMPLE * range_limit = cinfo->sample_range_limit; |
| register int * Crrtab = Cr_r_tab; |
| register int * Cbbtab = Cb_b_tab; |
| register INT32 * Crgtab = Cr_g_tab; |
| register INT32 * Cbgtab = Cb_g_tab; |
| int row; |
| SHIFT_TEMPS |
| |
| for (row = 0; row < num_rows; row++) { |
| inptr0 = input_data[0][row]; |
| inptr1 = input_data[1][row]; |
| inptr2 = input_data[2][row]; |
| outptr0 = output_data[0][row]; |
| outptr1 = output_data[1][row]; |
| outptr2 = output_data[2][row]; |
| for (col = 0; col < num_cols; col++) { |
| y = GETJSAMPLE(inptr0[col]); |
| cb = GETJSAMPLE(inptr1[col]); |
| cr = GETJSAMPLE(inptr2[col]); |
| /* Note: if the inputs were computed directly from RGB values, |
| * range-limiting would be unnecessary here; but due to possible |
| * noise in the DCT/IDCT phase, we do need to apply range limits. |
| */ |
| outptr0[col] = range_limit[y + Crrtab[cr]]; /* red */ |
| outptr1[col] = range_limit[y + /* green */ |
| ((int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], |
| SCALEBITS))]; |
| outptr2[col] = range_limit[y + Cbbtab[cb]]; /* blue */ |
| } |
| } |
| } |
| |
| |
| /* |
| * Finish up at the end of the file. |
| */ |
| |
| METHODDEF void |
| ycc_rgb_term (decompress_info_ptr cinfo) |
| { |
| /* no work (we let free_all release the workspace) */ |
| } |
| |
| |
| /**************** Cases other than YCbCr -> RGB **************/ |
| |
| |
| /* |
| * Initialize for colorspace conversion. |
| */ |
| |
| METHODDEF void |
| null_init (decompress_info_ptr cinfo) |
| /* colorout_init for cases where no setup is needed */ |
| { |
| /* no work needed */ |
| } |
| |
| |
| /* |
| * Color conversion for no colorspace change: just copy the data. |
| */ |
| |
| METHODDEF void |
| null_convert (decompress_info_ptr cinfo, int num_rows, long num_cols, |
| JSAMPIMAGE input_data, JSAMPIMAGE output_data) |
| { |
| short ci; |
| |
| for (ci = 0; ci < cinfo->num_components; ci++) { |
| jcopy_sample_rows(input_data[ci], 0, output_data[ci], 0, |
| num_rows, num_cols); |
| } |
| } |
| |
| |
| /* |
| * Color conversion for grayscale: just copy the data. |
| * This also works for YCbCr/YIQ -> grayscale conversion, in which |
| * we just copy the Y (luminance) component and ignore chrominance. |
| */ |
| |
| METHODDEF void |
| grayscale_convert (decompress_info_ptr cinfo, int num_rows, long num_cols, |
| JSAMPIMAGE input_data, JSAMPIMAGE output_data) |
| { |
| jcopy_sample_rows(input_data[0], 0, output_data[0], 0, |
| num_rows, num_cols); |
| } |
| |
| |
| /* |
| * Finish up at the end of the file. |
| */ |
| |
| METHODDEF void |
| null_term (decompress_info_ptr cinfo) |
| /* colorout_term for cases where no teardown is needed */ |
| { |
| /* no work needed */ |
| } |
| |
| |
| |
| /* |
| * The method selection routine for output colorspace conversion. |
| */ |
| |
| GLOBAL void |
| jseldcolor (decompress_info_ptr cinfo) |
| { |
| /* Make sure num_components agrees with jpeg_color_space */ |
| switch (cinfo->jpeg_color_space) { |
| case CS_GRAYSCALE: |
| if (cinfo->num_components != 1) |
| ERREXIT(cinfo->emethods, "Bogus JPEG colorspace"); |
| break; |
| |
| case CS_RGB: |
| case CS_YCbCr: |
| case CS_YIQ: |
| if (cinfo->num_components != 3) |
| ERREXIT(cinfo->emethods, "Bogus JPEG colorspace"); |
| break; |
| |
| case CS_CMYK: |
| if (cinfo->num_components != 4) |
| ERREXIT(cinfo->emethods, "Bogus JPEG colorspace"); |
| break; |
| |
| default: |
| ERREXIT(cinfo->emethods, "Unsupported JPEG colorspace"); |
| break; |
| } |
| |
| /* Set color_out_comps and conversion method based on requested space */ |
| switch (cinfo->out_color_space) { |
| case CS_GRAYSCALE: |
| cinfo->color_out_comps = 1; |
| if (cinfo->jpeg_color_space == CS_GRAYSCALE || |
| cinfo->jpeg_color_space == CS_YCbCr || |
| cinfo->jpeg_color_space == CS_YIQ) { |
| cinfo->methods->color_convert = grayscale_convert; |
| cinfo->methods->colorout_init = null_init; |
| cinfo->methods->colorout_term = null_term; |
| } else |
| ERREXIT(cinfo->emethods, "Unsupported color conversion request"); |
| break; |
| |
| case CS_RGB: |
| cinfo->color_out_comps = 3; |
| if (cinfo->jpeg_color_space == CS_YCbCr) { |
| cinfo->methods->color_convert = ycc_rgb_convert; |
| cinfo->methods->colorout_init = ycc_rgb_init; |
| cinfo->methods->colorout_term = ycc_rgb_term; |
| } else if (cinfo->jpeg_color_space == CS_RGB) { |
| cinfo->methods->color_convert = null_convert; |
| cinfo->methods->colorout_init = null_init; |
| cinfo->methods->colorout_term = null_term; |
| } else |
| ERREXIT(cinfo->emethods, "Unsupported color conversion request"); |
| break; |
| |
| default: |
| /* Permit null conversion from CMYK or YCbCr to same output space */ |
| if (cinfo->out_color_space == cinfo->jpeg_color_space) { |
| cinfo->color_out_comps = cinfo->num_components; |
| cinfo->methods->color_convert = null_convert; |
| cinfo->methods->colorout_init = null_init; |
| cinfo->methods->colorout_term = null_term; |
| } else /* unsupported non-null conversion */ |
| ERREXIT(cinfo->emethods, "Unsupported color conversion request"); |
| break; |
| } |
| |
| if (cinfo->quantize_colors) |
| cinfo->final_out_comps = 1; /* single colormapped output component */ |
| else |
| cinfo->final_out_comps = cinfo->color_out_comps; |
| } |