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Diffstat (limited to 'src/jpeg-6/jdcolor.c')
| -rw-r--r-- | src/jpeg-6/jdcolor.c | 367 |
1 files changed, 367 insertions, 0 deletions
diff --git a/src/jpeg-6/jdcolor.c b/src/jpeg-6/jdcolor.c new file mode 100644 index 0000000..b2bdf6e --- /dev/null +++ b/src/jpeg-6/jdcolor.c @@ -0,0 +1,367 @@ +/* + * jdcolor.c + * + * Copyright (C) 1991-1995, 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. + */ + +#define JPEG_INTERNALS +#include "jinclude.h" +#include "jpeglib.h" + + +/* Private subobject */ + +typedef struct { + struct jpeg_color_deconverter pub; /* public fields */ + + /* Private state for YCC->RGB conversion */ + int * Cr_r_tab; /* => table for Cr to R conversion */ + int * Cb_b_tab; /* => table for Cb to B conversion */ + INT32 * Cr_g_tab; /* => table for Cr to G conversion */ + INT32 * Cb_g_tab; /* => table for Cb to G conversion */ +} my_color_deconverter; + +typedef my_color_deconverter * my_cconvert_ptr; + + +/**************** 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 CENTERJSAMPLE. + * (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. + */ + +#define SCALEBITS 16 /* speediest right-shift on some machines */ +#define ONE_HALF ((INT32) 1 << (SCALEBITS-1)) +#define FIX(x) ((INT32) ((x) * (1L<<SCALEBITS) + 0.5)) + + +/* + * Initialize tables for YCC->RGB colorspace conversion. + */ + +LOCAL void +build_ycc_rgb_table (j_decompress_ptr cinfo) +{ + my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert; + int i; + INT32 x; + SHIFT_TEMPS + + cconvert->Cr_r_tab = (int *) + (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, + (MAXJSAMPLE+1) * SIZEOF(int)); + cconvert->Cb_b_tab = (int *) + (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, + (MAXJSAMPLE+1) * SIZEOF(int)); + cconvert->Cr_g_tab = (INT32 *) + (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, + (MAXJSAMPLE+1) * SIZEOF(INT32)); + cconvert->Cb_g_tab = (INT32 *) + (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, + (MAXJSAMPLE+1) * SIZEOF(INT32)); + + for (i = 0, x = -CENTERJSAMPLE; i <= MAXJSAMPLE; i++, x++) { + /* i is the actual input pixel value, in the range 0..MAXJSAMPLE */ + /* The Cb or Cr value we are thinking of is x = i - CENTERJSAMPLE */ + /* Cr=>R value is nearest int to 1.40200 * x */ + cconvert->Cr_r_tab[i] = (int) + RIGHT_SHIFT(FIX(1.40200) * x + ONE_HALF, SCALEBITS); + /* Cb=>B value is nearest int to 1.77200 * x */ + cconvert->Cb_b_tab[i] = (int) + RIGHT_SHIFT(FIX(1.77200) * x + ONE_HALF, SCALEBITS); + /* Cr=>G value is scaled-up -0.71414 * x */ + cconvert->Cr_g_tab[i] = (- FIX(0.71414)) * x; + /* Cb=>G value is scaled-up -0.34414 * x */ + /* We also add in ONE_HALF so that need not do it in inner loop */ + cconvert->Cb_g_tab[i] = (- FIX(0.34414)) * x + ONE_HALF; + } +} + + +/* + * Convert some rows of samples to the output colorspace. + * + * Note that we change from noninterleaved, one-plane-per-component format + * to interleaved-pixel format. The output buffer is therefore three times + * as wide as the input buffer. + * A starting row offset is provided only for the input buffer. The caller + * can easily adjust the passed output_buf value to accommodate any row + * offset required on that side. + */ + +METHODDEF void +ycc_rgb_convert (j_decompress_ptr cinfo, + JSAMPIMAGE input_buf, JDIMENSION input_row, + JSAMPARRAY output_buf, int num_rows) +{ + my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert; + register int y, cb, cr; + register JSAMPROW outptr; + register JSAMPROW inptr0, inptr1, inptr2; + register JDIMENSION col; + JDIMENSION num_cols = cinfo->output_width; + /* copy these pointers into registers if possible */ + register JSAMPLE * range_limit = cinfo->sample_range_limit; + register int * Crrtab = cconvert->Cr_r_tab; + register int * Cbbtab = cconvert->Cb_b_tab; + register INT32 * Crgtab = cconvert->Cr_g_tab; + register INT32 * Cbgtab = cconvert->Cb_g_tab; + SHIFT_TEMPS + + while (--num_rows >= 0) { + inptr0 = input_buf[0][input_row]; + inptr1 = input_buf[1][input_row]; + inptr2 = input_buf[2][input_row]; + input_row++; + outptr = *output_buf++; + for (col = 0; col < num_cols; col++) { + y = GETJSAMPLE(inptr0[col]); + cb = GETJSAMPLE(inptr1[col]); + cr = GETJSAMPLE(inptr2[col]); + /* Range-limiting is essential due to noise introduced by DCT losses. */ + outptr[RGB_RED] = range_limit[y + Crrtab[cr]]; + outptr[RGB_GREEN] = range_limit[y + + ((int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], + SCALEBITS))]; + outptr[RGB_BLUE] = range_limit[y + Cbbtab[cb]]; + outptr += RGB_PIXELSIZE; + } + } +} + + +/**************** Cases other than YCbCr -> RGB **************/ + + +/* + * Color conversion for no colorspace change: just copy the data, + * converting from separate-planes to interleaved representation. + */ + +METHODDEF void +null_convert (j_decompress_ptr cinfo, + JSAMPIMAGE input_buf, JDIMENSION input_row, + JSAMPARRAY output_buf, int num_rows) +{ + register JSAMPROW inptr, outptr; + register JDIMENSION count; + register int num_components = cinfo->num_components; + JDIMENSION num_cols = cinfo->output_width; + int ci; + + while (--num_rows >= 0) { + for (ci = 0; ci < num_components; ci++) { + inptr = input_buf[ci][input_row]; + outptr = output_buf[0] + ci; + for (count = num_cols; count > 0; count--) { + *outptr = *inptr++; /* needn't bother with GETJSAMPLE() here */ + outptr += num_components; + } + } + input_row++; + output_buf++; + } +} + + +/* + * Color conversion for grayscale: just copy the data. + * This also works for YCbCr -> grayscale conversion, in which + * we just copy the Y (luminance) component and ignore chrominance. + */ + +METHODDEF void +grayscale_convert (j_decompress_ptr cinfo, + JSAMPIMAGE input_buf, JDIMENSION input_row, + JSAMPARRAY output_buf, int num_rows) +{ + jcopy_sample_rows(input_buf[0], (int) input_row, output_buf, 0, + num_rows, cinfo->output_width); +} + + +/* + * Adobe-style YCCK->CMYK conversion. + * We convert YCbCr to R=1-C, G=1-M, and B=1-Y using the same + * conversion as above, while passing K (black) unchanged. + * We assume build_ycc_rgb_table has been called. + */ + +METHODDEF void +ycck_cmyk_convert (j_decompress_ptr cinfo, + JSAMPIMAGE input_buf, JDIMENSION input_row, + JSAMPARRAY output_buf, int num_rows) +{ + my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert; + register int y, cb, cr; + register JSAMPROW outptr; + register JSAMPROW inptr0, inptr1, inptr2, inptr3; + register JDIMENSION col; + JDIMENSION num_cols = cinfo->output_width; + /* copy these pointers into registers if possible */ + register JSAMPLE * range_limit = cinfo->sample_range_limit; + register int * Crrtab = cconvert->Cr_r_tab; + register int * Cbbtab = cconvert->Cb_b_tab; + register INT32 * Crgtab = cconvert->Cr_g_tab; + register INT32 * Cbgtab = cconvert->Cb_g_tab; + SHIFT_TEMPS + + while (--num_rows >= 0) { + inptr0 = input_buf[0][input_row]; + inptr1 = input_buf[1][input_row]; + inptr2 = input_buf[2][input_row]; + inptr3 = input_buf[3][input_row]; + input_row++; + outptr = *output_buf++; + for (col = 0; col < num_cols; col++) { + y = GETJSAMPLE(inptr0[col]); + cb = GETJSAMPLE(inptr1[col]); + cr = GETJSAMPLE(inptr2[col]); + /* Range-limiting is essential due to noise introduced by DCT losses. */ + outptr[0] = range_limit[MAXJSAMPLE - (y + Crrtab[cr])]; /* red */ + outptr[1] = range_limit[MAXJSAMPLE - (y + /* green */ + ((int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], + SCALEBITS)))]; + outptr[2] = range_limit[MAXJSAMPLE - (y + Cbbtab[cb])]; /* blue */ + /* K passes through unchanged */ + outptr[3] = inptr3[col]; /* don't need GETJSAMPLE here */ + outptr += 4; + } + } +} + + +/* + * Empty method for start_pass. + */ + +METHODDEF void +start_pass_dcolor (j_decompress_ptr cinfo) +{ + /* no work needed */ +} + + +/* + * Module initialization routine for output colorspace conversion. + */ + +GLOBAL void +jinit_color_deconverter (j_decompress_ptr cinfo) +{ + my_cconvert_ptr cconvert; + int ci; + + cconvert = (my_cconvert_ptr) + (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, + SIZEOF(my_color_deconverter)); + cinfo->cconvert = (struct jpeg_color_deconverter *) cconvert; + cconvert->pub.start_pass = start_pass_dcolor; + + /* Make sure num_components agrees with jpeg_color_space */ + switch (cinfo->jpeg_color_space) { + case JCS_GRAYSCALE: + if (cinfo->num_components != 1) + ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); + break; + + case JCS_RGB: + case JCS_YCbCr: + if (cinfo->num_components != 3) + ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); + break; + + case JCS_CMYK: + case JCS_YCCK: + if (cinfo->num_components != 4) + ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); + break; + + default: /* JCS_UNKNOWN can be anything */ + if (cinfo->num_components < 1) + ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); + break; + } + + /* Set out_color_components and conversion method based on requested space. + * Also clear the component_needed flags for any unused components, + * so that earlier pipeline stages can avoid useless computation. + */ + + switch (cinfo->out_color_space) { + case JCS_GRAYSCALE: + cinfo->out_color_components = 1; + if (cinfo->jpeg_color_space == JCS_GRAYSCALE || + cinfo->jpeg_color_space == JCS_YCbCr) { + cconvert->pub.color_convert = grayscale_convert; + /* For color->grayscale conversion, only the Y (0) component is needed */ + for (ci = 1; ci < cinfo->num_components; ci++) + cinfo->comp_info[ci].component_needed = FALSE; + } else + ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); + break; + + case JCS_RGB: + cinfo->out_color_components = RGB_PIXELSIZE; + if (cinfo->jpeg_color_space == JCS_YCbCr) { + cconvert->pub.color_convert = ycc_rgb_convert; + build_ycc_rgb_table(cinfo); + } else if (cinfo->jpeg_color_space == JCS_RGB && RGB_PIXELSIZE == 3) { + cconvert->pub.color_convert = null_convert; + } else + ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); + break; + + case JCS_CMYK: + cinfo->out_color_components = 4; + if (cinfo->jpeg_color_space == JCS_YCCK) { + cconvert->pub.color_convert = ycck_cmyk_convert; + build_ycc_rgb_table(cinfo); + } else if (cinfo->jpeg_color_space == JCS_CMYK) { + cconvert->pub.color_convert = null_convert; + } else + ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); + break; + + default: + /* Permit null conversion to same output space */ + if (cinfo->out_color_space == cinfo->jpeg_color_space) { + cinfo->out_color_components = cinfo->num_components; + cconvert->pub.color_convert = null_convert; + } else /* unsupported non-null conversion */ + ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); + break; + } + + if (cinfo->quantize_colors) + cinfo->output_components = 1; /* single colormapped output component */ + else + cinfo->output_components = cinfo->out_color_components; +} |