/*

 * jccolor.c

 *

 * Copyright (C) 1991-1996, 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 input colorspace conversion routines.

 */



#define JPEG_INTERNALS

#include "jinclude.h"

#include "jpeglib.h"





/* Private subobject */



typedef struct {

  struct jpeg_color_converter pub; /* public fields */



  /* Private state for RGB->YCC conversion */

  INT32 * rgb_ycc_tab;		/* => table for RGB to YCbCr conversion */

} my_color_converter;



typedef my_color_converter * my_cconvert_ptr;





/**************** RGB -> YCbCr 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

 *	Y  =  0.29900 * R + 0.58700 * G + 0.11400 * B

 *	Cb = -0.16874 * R - 0.33126 * G + 0.50000 * B  + CENTERJSAMPLE

 *	Cr =  0.50000 * R - 0.41869 * G - 0.08131 * B  + CENTERJSAMPLE

 * (These numbers are derived from TIFF 6.0 section 21, dated 3-June-92.)

 * Note: older versions of the IJG code used a zero offset of MAXJSAMPLE/2,

 * rather than CENTERJSAMPLE, for Cb and Cr.  This gave equal positive and

 * negative swings for Cb/Cr, but meant that grayscale values (Cb=Cr=0)

 * were not represented exactly.  Now we sacrifice exact representation of

 * maximum red and maximum blue in order to get exact grayscales.

 *

 * 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.

 *

 * For even more speed, we avoid doing any multiplications in the inner loop

 * by precalculating the constants times R,G,B 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 CENTERJSAMPLE offsets and the rounding fudge-factor of 0.5 are included

 * in the tables to save adding them separately in the inner loop.

 */



#define SCALEBITS	16	/* speediest right-shift on some machines */

#define CBCR_OFFSET	((INT32) CENTERJSAMPLE << SCALEBITS)

#define ONE_HALF	((INT32) 1 << (SCALEBITS-1))

#define FIX(x)		((INT32) ((x) * (1L<<SCALEBITS) + 0.5))



/* We allocate one big table and divide it up into eight parts, instead of

 * doing eight alloc_small requests.  This lets us use a single table base

 * address, which can be held in a register in the inner loops on many

 * machines (more than can hold all eight addresses, anyway).

 */



#define R_Y_OFF		0			/* offset to R => Y section */

#define G_Y_OFF		(1*(MAXJSAMPLE+1))	/* offset to G => Y section */

#define B_Y_OFF		(2*(MAXJSAMPLE+1))	/* etc. */

#define R_CB_OFF	(3*(MAXJSAMPLE+1))

#define G_CB_OFF	(4*(MAXJSAMPLE+1))

#define B_CB_OFF	(5*(MAXJSAMPLE+1))

#define R_CR_OFF	B_CB_OFF		/* B=>Cb, R=>Cr are the same */

#define G_CR_OFF	(6*(MAXJSAMPLE+1))

#define B_CR_OFF	(7*(MAXJSAMPLE+1))

#define TABLE_SIZE	(8*(MAXJSAMPLE+1))





/*

 * Initialize for RGB->YCC colorspace conversion.

 */



METHODDEF(void)

rgb_ycc_start (j_compress_ptr cinfo)

{

  my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;

  INT32 * rgb_ycc_tab;

  INT32 i;



  /* Allocate and fill in the conversion tables. */

  cconvert->rgb_ycc_tab = rgb_ycc_tab = (INT32 *)

    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,

				(TABLE_SIZE * SIZEOF(INT32)));



  for (i = 0; i <= MAXJSAMPLE; i++) {

    rgb_ycc_tab[i+R_Y_OFF] = FIX(0.29900) * i;

    rgb_ycc_tab[i+G_Y_OFF] = FIX(0.58700) * i;

    rgb_ycc_tab[i+B_Y_OFF] = FIX(0.11400) * i     + ONE_HALF;

    rgb_ycc_tab[i+R_CB_OFF] = (-FIX(0.16874)) * i;

    rgb_ycc_tab[i+G_CB_OFF] = (-FIX(0.33126)) * i;

    /* We use a rounding fudge-factor of 0.5-epsilon for Cb and Cr.

     * This ensures that the maximum output will round to MAXJSAMPLE

     * not MAXJSAMPLE+1, and thus that we don't have to range-limit.

     */

    rgb_ycc_tab[i+B_CB_OFF] = FIX(0.50000) * i    + CBCR_OFFSET + ONE_HALF-1;

/*  B=>Cb and R=>Cr tables are the same

    rgb_ycc_tab[i+R_CR_OFF] = FIX(0.50000) * i    + CBCR_OFFSET + ONE_HALF-1;

*/

    rgb_ycc_tab[i+G_CR_OFF] = (-FIX(0.41869)) * i;

    rgb_ycc_tab[i+B_CR_OFF] = (-FIX(0.08131)) * i;

  }

}





/*

 * Convert some rows of samples to the JPEG colorspace.

 *

 * Note that we change from the application's interleaved-pixel format

 * to our internal noninterleaved, one-plane-per-component format.

 * The input buffer is therefore three times as wide as the output buffer.

 *

 * A starting row offset is provided only for the output buffer.  The caller

 * can easily adjust the passed input_buf value to accommodate any row

 * offset required on that side.

 */



METHODDEF(void)

rgb_ycc_convert (j_compress_ptr cinfo,

		 JSAMPARRAY input_buf, JSAMPIMAGE output_buf,

		 JDIMENSION output_row, int num_rows)

{

  my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;

  register int r, g, b;

  register INT32 * ctab = cconvert->rgb_ycc_tab;

  register JSAMPROW inptr;

  register JSAMPROW outptr0, outptr1, outptr2;

  register JDIMENSION col;

  JDIMENSION num_cols = cinfo->image_width;



  while (--num_rows >= 0) {

    inptr = *input_buf++;

    outptr0 = output_buf[0][output_row];

    outptr1 = output_buf[1][output_row];

    outptr2 = output_buf[2][output_row];

    output_row++;

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

      r = GETJSAMPLE(inptr[RGB_RED]);

      g = GETJSAMPLE(inptr[RGB_GREEN]);

      b = GETJSAMPLE(inptr[RGB_BLUE]);

      inptr += RGB_PIXELSIZE;

      /* If the inputs are 0..MAXJSAMPLE, the outputs of these equations

       * must be too; we do not need an explicit range-limiting operation.

       * Hence the value being shifted is never negative, and we don't

       * need the general RIGHT_SHIFT macro.

       */

      /* Y */

      outptr0[col] = (JSAMPLE)

		((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF])

		 >> SCALEBITS);

      /* Cb */

      outptr1[col] = (JSAMPLE)

		((ctab[r+R_CB_OFF] + ctab[g+G_CB_OFF] + ctab[b+B_CB_OFF])

		 >> SCALEBITS);

      /* Cr */

      outptr2[col] = (JSAMPLE)

		((ctab[r+R_CR_OFF] + ctab[g+G_CR_OFF] + ctab[b+B_CR_OFF])

		 >> SCALEBITS);

    }

  }

}





/**************** Cases other than RGB -> YCbCr **************/





/*

 * Convert some rows of samples to the JPEG colorspace.

 * This version handles RGB->grayscale conversion, which is the same

 * as the RGB->Y portion of RGB->YCbCr.

 * We assume rgb_ycc_start has been called (we only use the Y tables).

 */



METHODDEF(void)

rgb_gray_convert (j_compress_ptr cinfo,

		  JSAMPARRAY input_buf, JSAMPIMAGE output_buf,

		  JDIMENSION output_row, int num_rows)

{

  my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;

  register int r, g, b;

  register INT32 * ctab = cconvert->rgb_ycc_tab;

  register JSAMPROW inptr;

  register JSAMPROW outptr;

  register JDIMENSION col;

  JDIMENSION num_cols = cinfo->image_width;



  while (--num_rows >= 0) {

    inptr = *input_buf++;

    outptr = output_buf[0][output_row];

    output_row++;

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

      r = GETJSAMPLE(inptr[RGB_RED]);

      g = GETJSAMPLE(inptr[RGB_GREEN]);

      b = GETJSAMPLE(inptr[RGB_BLUE]);

      inptr += RGB_PIXELSIZE;

      /* Y */

      outptr[col] = (JSAMPLE)

		((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF])

		 >> SCALEBITS);

    }

  }

}





/*

 * Convert some rows of samples to the JPEG colorspace.

 * This version handles Adobe-style CMYK->YCCK conversion,

 * where we convert R=1-C, G=1-M, and B=1-Y to YCbCr using the same

 * conversion as above, while passing K (black) unchanged.

 * We assume rgb_ycc_start has been called.

 */



METHODDEF(void)

cmyk_ycck_convert (j_compress_ptr cinfo,

		   JSAMPARRAY input_buf, JSAMPIMAGE output_buf,

		   JDIMENSION output_row, int num_rows)

{

  my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;

  register int r, g, b;

  register INT32 * ctab = cconvert->rgb_ycc_tab;

  register JSAMPROW inptr;

  register JSAMPROW outptr0, outptr1, outptr2, outptr3;

  register JDIMENSION col;

  JDIMENSION num_cols = cinfo->image_width;



  while (--num_rows >= 0) {

    inptr = *input_buf++;

    outptr0 = output_buf[0][output_row];

    outptr1 = output_buf[1][output_row];

    outptr2 = output_buf[2][output_row];

    outptr3 = output_buf[3][output_row];

    output_row++;

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

      r = MAXJSAMPLE - GETJSAMPLE(inptr[0]);

      g = MAXJSAMPLE - GETJSAMPLE(inptr[1]);

      b = MAXJSAMPLE - GETJSAMPLE(inptr[2]);

      /* K passes through as-is */

      outptr3[col] = inptr[3];	/* don't need GETJSAMPLE here */

      inptr += 4;

      /* If the inputs are 0..MAXJSAMPLE, the outputs of these equations

       * must be too; we do not need an explicit range-limiting operation.

       * Hence the value being shifted is never negative, and we don't

       * need the general RIGHT_SHIFT macro.

       */

      /* Y */

      outptr0[col] = (JSAMPLE)

		((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF])

		 >> SCALEBITS);

      /* Cb */

      outptr1[col] = (JSAMPLE)

		((ctab[r+R_CB_OFF] + ctab[g+G_CB_OFF] + ctab[b+B_CB_OFF])

		 >> SCALEBITS);

      /* Cr */

      outptr2[col] = (JSAMPLE)

		((ctab[r+R_CR_OFF] + ctab[g+G_CR_OFF] + ctab[b+B_CR_OFF])

		 >> SCALEBITS);

    }

  }

}





/*

 * Convert some rows of samples to the JPEG colorspace.

 * This version handles grayscale output with no conversion.

 * The source can be either plain grayscale or YCbCr (since Y == gray).

 */



METHODDEF(void)

grayscale_convert (j_compress_ptr cinfo,

		   JSAMPARRAY input_buf, JSAMPIMAGE output_buf,

		   JDIMENSION output_row, int num_rows)

{

  register JSAMPROW inptr;

  register JSAMPROW outptr;

  register JDIMENSION col;

  JDIMENSION num_cols = cinfo->image_width;

  int instride = cinfo->input_components;



  while (--num_rows >= 0) {

    inptr = *input_buf++;

    outptr = output_buf[0][output_row];

    output_row++;

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

      outptr[col] = inptr[0];	/* don't need GETJSAMPLE() here */

      inptr += instride;

    }

  }

}





/*

 * Convert some rows of samples to the JPEG colorspace.

 * This version handles multi-component colorspaces without conversion.

 * We assume input_components == num_components.

 */



METHODDEF(void)

null_convert (j_compress_ptr cinfo,

	      JSAMPARRAY input_buf, JSAMPIMAGE output_buf,

	      JDIMENSION output_row, int num_rows)

{

  register JSAMPROW inptr;

  register JSAMPROW outptr;

  register JDIMENSION col;

  register int ci;

  int nc = cinfo->num_components;

  JDIMENSION num_cols = cinfo->image_width;



  while (--num_rows >= 0) {

    /* It seems fastest to make a separate pass for each component. */

    for (ci = 0; ci < nc; ci++) {

      inptr = *input_buf;

      outptr = output_buf[ci][output_row];

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

	outptr[col] = inptr[ci]; /* don't need GETJSAMPLE() here */

	inptr += nc;

      }

    }

    input_buf++;

    output_row++;

  }

}





/*

 * Empty method for start_pass.

 */



METHODDEF(void)

null_method (j_compress_ptr cinfo)

{

  /* no work needed */

}





/*

 * Module initialization routine for input colorspace conversion.

 */



GLOBAL(void)

jinit_color_converter (j_compress_ptr cinfo)

{

  my_cconvert_ptr cconvert;



  cconvert = (my_cconvert_ptr)

    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,

				SIZEOF(my_color_converter));

  cinfo->cconvert = (struct jpeg_color_converter *) cconvert;

  /* set start_pass to null method until we find out differently */

  cconvert->pub.start_pass = null_method;



  /* Make sure input_components agrees with in_color_space */

  switch (cinfo->in_color_space) {

  case JCS_GRAYSCALE:

    if (cinfo->input_components != 1)

      ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);

    break;



  case JCS_RGB:

#if RGB_PIXELSIZE != 3

    if (cinfo->input_components != RGB_PIXELSIZE)

      ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);

    break;

#endif /* else share code with YCbCr */



  case JCS_YCbCr:

    if (cinfo->input_components != 3)

      ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);

    break;



  case JCS_CMYK:

  case JCS_YCCK:

    if (cinfo->input_components != 4)

      ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);

    break;



  default:			/* JCS_UNKNOWN can be anything */

    if (cinfo->input_components < 1)

      ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);

    break;

  }



  /* Check num_components, set conversion method based on requested space */

  switch (cinfo->jpeg_color_space) {

  case JCS_GRAYSCALE:

    if (cinfo->num_components != 1)

      ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);

    if (cinfo->in_color_space == JCS_GRAYSCALE)

      cconvert->pub.color_convert = grayscale_convert;

    else if (cinfo->in_color_space == JCS_RGB) {

      cconvert->pub.start_pass = rgb_ycc_start;

      cconvert->pub.color_convert = rgb_gray_convert;

    } else if (cinfo->in_color_space == JCS_YCbCr)

      cconvert->pub.color_convert = grayscale_convert;

    else

      ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);

    break;



  case JCS_RGB:

    if (cinfo->num_components != 3)

      ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);

    if (cinfo->in_color_space == JCS_RGB && RGB_PIXELSIZE == 3)

      cconvert->pub.color_convert = null_convert;

    else

      ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);

    break;



  case JCS_YCbCr:

    if (cinfo->num_components != 3)

      ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);

    if (cinfo->in_color_space == JCS_RGB) {

      cconvert->pub.start_pass = rgb_ycc_start;

      cconvert->pub.color_convert = rgb_ycc_convert;

    } else if (cinfo->in_color_space == JCS_YCbCr)

      cconvert->pub.color_convert = null_convert;

    else

      ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);

    break;



  case JCS_CMYK:

    if (cinfo->num_components != 4)

      ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);

    if (cinfo->in_color_space == JCS_CMYK)

      cconvert->pub.color_convert = null_convert;

    else

      ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);

    break;



  case JCS_YCCK:

    if (cinfo->num_components != 4)

      ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);

    if (cinfo->in_color_space == JCS_CMYK) {

      cconvert->pub.start_pass = rgb_ycc_start;

      cconvert->pub.color_convert = cmyk_ycck_convert;

    } else if (cinfo->in_color_space == JCS_YCCK)

      cconvert->pub.color_convert = null_convert;

    else

      ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);

    break;



  default:			/* allow null conversion of JCS_UNKNOWN */

    if (cinfo->jpeg_color_space != cinfo->in_color_space ||

	cinfo->num_components != cinfo->input_components)

      ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);

    cconvert->pub.color_convert = null_convert;

    break;

  }

}

