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/*

 * jdcolor.c

 *

 * Copyright (C) 1991-1997, 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);

}

/*

 * Convert grayscale to RGB: just duplicate the graylevel three times.

 * This is provided to support applications that don't want to cope

 * with grayscale as a separate case.

 */

METHODDEF(void)

gray_rgb_convert (j_decompress_ptr cinfo,

		  JSAMPIMAGE input_buf, JDIMENSION input_row,

		  JSAMPARRAY output_buf, int num_rows)

{

  register JSAMPROW inptr, outptr;

  register JDIMENSION col;

  JDIMENSION num_cols = cinfo->output_width;

  while (--num_rows >= 0) {

    inptr = input_buf[0][input_row++];

    outptr = *output_buf++;

    for (col = 0; col < num_cols; col++) {

      /* We can dispense with GETJSAMPLE() here */

      outptr[RGB_RED] = outptr[RGB_GREEN] = outptr[RGB_BLUE] = inptr[col];

      outptr += RGB_PIXELSIZE;

    }

  }

}

/*

 * 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_GRAYSCALE) {

      cconvert->pub.color_convert = gray_rgb_convert;

    } 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;

}