/*
 * 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;
	}
}
