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459 lines
14 KiB
459 lines
14 KiB
/* |
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* jccolor.c |
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* |
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* Copyright (C) 1991-1996, Thomas G. Lane. |
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* This file is part of the Independent JPEG Group's software. |
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* For conditions of distribution and use, see the accompanying README file. |
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* |
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* This file contains input colorspace conversion routines. |
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*/ |
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#define JPEG_INTERNALS |
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#include "jinclude.h" |
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#include "jpeglib.h" |
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/* Private subobject */ |
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typedef struct { |
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struct jpeg_color_converter pub; /* public fields */ |
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/* Private state for RGB->YCC conversion */ |
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INT32 * rgb_ycc_tab; /* => table for RGB to YCbCr conversion */ |
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} my_color_converter; |
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typedef my_color_converter * my_cconvert_ptr; |
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/**************** RGB -> YCbCr conversion: most common case **************/ |
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/* |
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* YCbCr is defined per CCIR 601-1, except that Cb and Cr are |
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* normalized to the range 0..MAXJSAMPLE rather than -0.5 .. 0.5. |
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* The conversion equations to be implemented are therefore |
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* Y = 0.29900 * R + 0.58700 * G + 0.11400 * B |
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* Cb = -0.16874 * R - 0.33126 * G + 0.50000 * B + CENTERJSAMPLE |
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* Cr = 0.50000 * R - 0.41869 * G - 0.08131 * B + CENTERJSAMPLE |
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* (These numbers are derived from TIFF 6.0 section 21, dated 3-June-92.) |
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* Note: older versions of the IJG code used a zero offset of MAXJSAMPLE/2, |
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* rather than CENTERJSAMPLE, for Cb and Cr. This gave equal positive and |
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* negative swings for Cb/Cr, but meant that grayscale values (Cb=Cr=0) |
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* were not represented exactly. Now we sacrifice exact representation of |
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* maximum red and maximum blue in order to get exact grayscales. |
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* |
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* To avoid floating-point arithmetic, we represent the fractional constants |
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* as integers scaled up by 2^16 (about 4 digits precision); we have to divide |
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* the products by 2^16, with appropriate rounding, to get the correct answer. |
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* |
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* For even more speed, we avoid doing any multiplications in the inner loop |
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* by precalculating the constants times R,G,B for all possible values. |
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* For 8-bit JSAMPLEs this is very reasonable (only 256 entries per table); |
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* for 12-bit samples it is still acceptable. It's not very reasonable for |
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* 16-bit samples, but if you want lossless storage you shouldn't be changing |
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* colorspace anyway. |
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* The CENTERJSAMPLE offsets and the rounding fudge-factor of 0.5 are included |
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* in the tables to save adding them separately in the inner loop. |
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*/ |
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#define SCALEBITS 16 /* speediest right-shift on some machines */ |
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#define CBCR_OFFSET ((INT32) CENTERJSAMPLE << SCALEBITS) |
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#define ONE_HALF ((INT32) 1 << (SCALEBITS-1)) |
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#define FIX(x) ((INT32) ((x) * (1L<<SCALEBITS) + 0.5)) |
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/* We allocate one big table and divide it up into eight parts, instead of |
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* doing eight alloc_small requests. This lets us use a single table base |
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* address, which can be held in a register in the inner loops on many |
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* machines (more than can hold all eight addresses, anyway). |
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*/ |
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#define R_Y_OFF 0 /* offset to R => Y section */ |
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#define G_Y_OFF (1*(MAXJSAMPLE+1)) /* offset to G => Y section */ |
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#define B_Y_OFF (2*(MAXJSAMPLE+1)) /* etc. */ |
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#define R_CB_OFF (3*(MAXJSAMPLE+1)) |
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#define G_CB_OFF (4*(MAXJSAMPLE+1)) |
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#define B_CB_OFF (5*(MAXJSAMPLE+1)) |
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#define R_CR_OFF B_CB_OFF /* B=>Cb, R=>Cr are the same */ |
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#define G_CR_OFF (6*(MAXJSAMPLE+1)) |
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#define B_CR_OFF (7*(MAXJSAMPLE+1)) |
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#define TABLE_SIZE (8*(MAXJSAMPLE+1)) |
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/* |
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* Initialize for RGB->YCC colorspace conversion. |
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*/ |
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METHODDEF(void) |
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rgb_ycc_start (j_compress_ptr cinfo) |
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{ |
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my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert; |
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INT32 * rgb_ycc_tab; |
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INT32 i; |
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/* Allocate and fill in the conversion tables. */ |
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cconvert->rgb_ycc_tab = rgb_ycc_tab = (INT32 *) |
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(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, |
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(TABLE_SIZE * SIZEOF(INT32))); |
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for (i = 0; i <= MAXJSAMPLE; i++) { |
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rgb_ycc_tab[i+R_Y_OFF] = FIX(0.29900) * i; |
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rgb_ycc_tab[i+G_Y_OFF] = FIX(0.58700) * i; |
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rgb_ycc_tab[i+B_Y_OFF] = FIX(0.11400) * i + ONE_HALF; |
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rgb_ycc_tab[i+R_CB_OFF] = (-FIX(0.16874)) * i; |
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rgb_ycc_tab[i+G_CB_OFF] = (-FIX(0.33126)) * i; |
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/* We use a rounding fudge-factor of 0.5-epsilon for Cb and Cr. |
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* This ensures that the maximum output will round to MAXJSAMPLE |
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* not MAXJSAMPLE+1, and thus that we don't have to range-limit. |
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*/ |
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rgb_ycc_tab[i+B_CB_OFF] = FIX(0.50000) * i + CBCR_OFFSET + ONE_HALF-1; |
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/* B=>Cb and R=>Cr tables are the same |
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rgb_ycc_tab[i+R_CR_OFF] = FIX(0.50000) * i + CBCR_OFFSET + ONE_HALF-1; |
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*/ |
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rgb_ycc_tab[i+G_CR_OFF] = (-FIX(0.41869)) * i; |
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rgb_ycc_tab[i+B_CR_OFF] = (-FIX(0.08131)) * i; |
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} |
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} |
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/* |
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* Convert some rows of samples to the JPEG colorspace. |
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* |
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* Note that we change from the application's interleaved-pixel format |
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* to our internal noninterleaved, one-plane-per-component format. |
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* The input buffer is therefore three times as wide as the output buffer. |
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* |
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* A starting row offset is provided only for the output buffer. The caller |
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* can easily adjust the passed input_buf value to accommodate any row |
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* offset required on that side. |
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*/ |
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METHODDEF(void) |
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rgb_ycc_convert (j_compress_ptr cinfo, |
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JSAMPARRAY input_buf, JSAMPIMAGE output_buf, |
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JDIMENSION output_row, int num_rows) |
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{ |
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my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert; |
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int r, g, b; |
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INT32 * ctab = cconvert->rgb_ycc_tab; |
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JSAMPROW inptr; |
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JSAMPROW outptr0, outptr1, outptr2; |
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JDIMENSION col; |
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JDIMENSION num_cols = cinfo->image_width; |
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while (--num_rows >= 0) { |
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inptr = *input_buf++; |
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outptr0 = output_buf[0][output_row]; |
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outptr1 = output_buf[1][output_row]; |
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outptr2 = output_buf[2][output_row]; |
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output_row++; |
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for (col = 0; col < num_cols; col++) { |
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r = GETJSAMPLE(inptr[RGB_RED]); |
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g = GETJSAMPLE(inptr[RGB_GREEN]); |
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b = GETJSAMPLE(inptr[RGB_BLUE]); |
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inptr += RGB_PIXELSIZE; |
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/* If the inputs are 0..MAXJSAMPLE, the outputs of these equations |
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* must be too; we do not need an explicit range-limiting operation. |
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* Hence the value being shifted is never negative, and we don't |
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* need the general RIGHT_SHIFT macro. |
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*/ |
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/* Y */ |
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outptr0[col] = (JSAMPLE) |
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((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF]) |
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>> SCALEBITS); |
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/* Cb */ |
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outptr1[col] = (JSAMPLE) |
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((ctab[r+R_CB_OFF] + ctab[g+G_CB_OFF] + ctab[b+B_CB_OFF]) |
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>> SCALEBITS); |
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/* Cr */ |
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outptr2[col] = (JSAMPLE) |
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((ctab[r+R_CR_OFF] + ctab[g+G_CR_OFF] + ctab[b+B_CR_OFF]) |
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>> SCALEBITS); |
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} |
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} |
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} |
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/**************** Cases other than RGB -> YCbCr **************/ |
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/* |
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* Convert some rows of samples to the JPEG colorspace. |
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* This version handles RGB->grayscale conversion, which is the same |
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* as the RGB->Y portion of RGB->YCbCr. |
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* We assume rgb_ycc_start has been called (we only use the Y tables). |
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*/ |
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METHODDEF(void) |
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rgb_gray_convert (j_compress_ptr cinfo, |
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JSAMPARRAY input_buf, JSAMPIMAGE output_buf, |
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JDIMENSION output_row, int num_rows) |
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{ |
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my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert; |
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int r, g, b; |
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INT32 * ctab = cconvert->rgb_ycc_tab; |
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JSAMPROW inptr; |
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JSAMPROW outptr; |
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JDIMENSION col; |
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JDIMENSION num_cols = cinfo->image_width; |
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while (--num_rows >= 0) { |
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inptr = *input_buf++; |
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outptr = output_buf[0][output_row]; |
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output_row++; |
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for (col = 0; col < num_cols; col++) { |
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r = GETJSAMPLE(inptr[RGB_RED]); |
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g = GETJSAMPLE(inptr[RGB_GREEN]); |
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b = GETJSAMPLE(inptr[RGB_BLUE]); |
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inptr += RGB_PIXELSIZE; |
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/* Y */ |
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outptr[col] = (JSAMPLE) |
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((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF]) |
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>> SCALEBITS); |
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} |
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} |
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} |
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/* |
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* Convert some rows of samples to the JPEG colorspace. |
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* This version handles Adobe-style CMYK->YCCK conversion, |
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* where we convert R=1-C, G=1-M, and B=1-Y to YCbCr using the same |
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* conversion as above, while passing K (black) unchanged. |
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* We assume rgb_ycc_start has been called. |
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*/ |
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METHODDEF(void) |
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cmyk_ycck_convert (j_compress_ptr cinfo, |
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JSAMPARRAY input_buf, JSAMPIMAGE output_buf, |
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JDIMENSION output_row, int num_rows) |
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{ |
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my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert; |
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int r, g, b; |
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INT32 * ctab = cconvert->rgb_ycc_tab; |
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JSAMPROW inptr; |
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JSAMPROW outptr0, outptr1, outptr2, outptr3; |
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JDIMENSION col; |
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JDIMENSION num_cols = cinfo->image_width; |
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while (--num_rows >= 0) { |
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inptr = *input_buf++; |
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outptr0 = output_buf[0][output_row]; |
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outptr1 = output_buf[1][output_row]; |
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outptr2 = output_buf[2][output_row]; |
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outptr3 = output_buf[3][output_row]; |
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output_row++; |
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for (col = 0; col < num_cols; col++) { |
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r = MAXJSAMPLE - GETJSAMPLE(inptr[0]); |
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g = MAXJSAMPLE - GETJSAMPLE(inptr[1]); |
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b = MAXJSAMPLE - GETJSAMPLE(inptr[2]); |
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/* K passes through as-is */ |
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outptr3[col] = inptr[3]; /* don't need GETJSAMPLE here */ |
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inptr += 4; |
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/* If the inputs are 0..MAXJSAMPLE, the outputs of these equations |
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* must be too; we do not need an explicit range-limiting operation. |
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* Hence the value being shifted is never negative, and we don't |
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* need the general RIGHT_SHIFT macro. |
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*/ |
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/* Y */ |
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outptr0[col] = (JSAMPLE) |
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((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF]) |
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>> SCALEBITS); |
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/* Cb */ |
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outptr1[col] = (JSAMPLE) |
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((ctab[r+R_CB_OFF] + ctab[g+G_CB_OFF] + ctab[b+B_CB_OFF]) |
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>> SCALEBITS); |
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/* Cr */ |
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outptr2[col] = (JSAMPLE) |
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((ctab[r+R_CR_OFF] + ctab[g+G_CR_OFF] + ctab[b+B_CR_OFF]) |
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>> SCALEBITS); |
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} |
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} |
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} |
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/* |
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* Convert some rows of samples to the JPEG colorspace. |
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* This version handles grayscale output with no conversion. |
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* The source can be either plain grayscale or YCbCr (since Y == gray). |
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*/ |
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METHODDEF(void) |
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grayscale_convert (j_compress_ptr cinfo, |
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JSAMPARRAY input_buf, JSAMPIMAGE output_buf, |
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JDIMENSION output_row, int num_rows) |
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{ |
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JSAMPROW inptr; |
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JSAMPROW outptr; |
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JDIMENSION col; |
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JDIMENSION num_cols = cinfo->image_width; |
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int instride = cinfo->input_components; |
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while (--num_rows >= 0) { |
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inptr = *input_buf++; |
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outptr = output_buf[0][output_row]; |
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output_row++; |
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for (col = 0; col < num_cols; col++) { |
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outptr[col] = inptr[0]; /* don't need GETJSAMPLE() here */ |
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inptr += instride; |
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} |
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} |
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} |
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/* |
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* Convert some rows of samples to the JPEG colorspace. |
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* This version handles multi-component colorspaces without conversion. |
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* We assume input_components == num_components. |
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*/ |
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METHODDEF(void) |
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null_convert (j_compress_ptr cinfo, |
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JSAMPARRAY input_buf, JSAMPIMAGE output_buf, |
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JDIMENSION output_row, int num_rows) |
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{ |
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JSAMPROW inptr; |
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JSAMPROW outptr; |
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JDIMENSION col; |
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int ci; |
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int nc = cinfo->num_components; |
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JDIMENSION num_cols = cinfo->image_width; |
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while (--num_rows >= 0) { |
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/* It seems fastest to make a separate pass for each component. */ |
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for (ci = 0; ci < nc; ci++) { |
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inptr = *input_buf; |
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outptr = output_buf[ci][output_row]; |
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for (col = 0; col < num_cols; col++) { |
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outptr[col] = inptr[ci]; /* don't need GETJSAMPLE() here */ |
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inptr += nc; |
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} |
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} |
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input_buf++; |
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output_row++; |
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} |
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} |
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/* |
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* Empty method for start_pass. |
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*/ |
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METHODDEF(void) |
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null_method (j_compress_ptr cinfo) |
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{ |
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/* no work needed */ |
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} |
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/* |
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* Module initialization routine for input colorspace conversion. |
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*/ |
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GLOBAL(void) |
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jinit_color_converter (j_compress_ptr cinfo) |
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{ |
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my_cconvert_ptr cconvert; |
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cconvert = (my_cconvert_ptr) |
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(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, |
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SIZEOF(my_color_converter)); |
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cinfo->cconvert = (struct jpeg_color_converter *) cconvert; |
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/* set start_pass to null method until we find out differently */ |
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cconvert->pub.start_pass = null_method; |
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/* Make sure input_components agrees with in_color_space */ |
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switch (cinfo->in_color_space) { |
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case JCS_GRAYSCALE: |
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if (cinfo->input_components != 1) |
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ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE); |
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break; |
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case JCS_RGB: |
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#if RGB_PIXELSIZE != 3 |
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if (cinfo->input_components != RGB_PIXELSIZE) |
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ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE); |
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break; |
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#endif /* else share code with YCbCr */ |
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case JCS_YCbCr: |
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if (cinfo->input_components != 3) |
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ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE); |
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break; |
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case JCS_CMYK: |
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case JCS_YCCK: |
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if (cinfo->input_components != 4) |
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ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE); |
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break; |
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default: /* JCS_UNKNOWN can be anything */ |
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if (cinfo->input_components < 1) |
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ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE); |
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break; |
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} |
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/* Check num_components, set conversion method based on requested space */ |
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switch (cinfo->jpeg_color_space) { |
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case JCS_GRAYSCALE: |
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if (cinfo->num_components != 1) |
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ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); |
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if (cinfo->in_color_space == JCS_GRAYSCALE) |
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cconvert->pub.color_convert = grayscale_convert; |
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else if (cinfo->in_color_space == JCS_RGB) { |
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cconvert->pub.start_pass = rgb_ycc_start; |
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cconvert->pub.color_convert = rgb_gray_convert; |
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} else if (cinfo->in_color_space == JCS_YCbCr) |
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cconvert->pub.color_convert = grayscale_convert; |
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else |
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ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); |
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break; |
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case JCS_RGB: |
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if (cinfo->num_components != 3) |
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ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); |
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if (cinfo->in_color_space == JCS_RGB && RGB_PIXELSIZE == 3) |
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cconvert->pub.color_convert = null_convert; |
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else |
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ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); |
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break; |
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case JCS_YCbCr: |
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if (cinfo->num_components != 3) |
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ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); |
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if (cinfo->in_color_space == JCS_RGB) { |
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cconvert->pub.start_pass = rgb_ycc_start; |
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cconvert->pub.color_convert = rgb_ycc_convert; |
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} else if (cinfo->in_color_space == JCS_YCbCr) |
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cconvert->pub.color_convert = null_convert; |
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else |
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ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); |
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break; |
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case JCS_CMYK: |
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if (cinfo->num_components != 4) |
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ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); |
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if (cinfo->in_color_space == JCS_CMYK) |
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cconvert->pub.color_convert = null_convert; |
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else |
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ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); |
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break; |
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case JCS_YCCK: |
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if (cinfo->num_components != 4) |
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ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); |
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if (cinfo->in_color_space == JCS_CMYK) { |
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cconvert->pub.start_pass = rgb_ycc_start; |
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cconvert->pub.color_convert = cmyk_ycck_convert; |
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} else if (cinfo->in_color_space == JCS_YCCK) |
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cconvert->pub.color_convert = null_convert; |
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else |
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ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); |
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break; |
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default: /* allow null conversion of JCS_UNKNOWN */ |
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if (cinfo->jpeg_color_space != cinfo->in_color_space || |
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cinfo->num_components != cinfo->input_components) |
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ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); |
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cconvert->pub.color_convert = null_convert; |
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break; |
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} |
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}
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