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