/*

 * jccolor.c

 *

 * This file was part of the Independent JPEG Group's software:

 * Copyright (C) 1991-1996, Thomas G. Lane.

 * libjpeg-turbo Modifications:

 * Copyright 2009 Pierre Ossman <ossman@cendio.se> for Cendio AB

 * Copyright (C) 2009-2012, 2015, 2022, D. R. Commander.

 * Copyright (C) 2014, MIPS Technologies, Inc., California.

 * For conditions of distribution and use, see the accompanying README.ijg

 * file.

 *

 * This file contains input colorspace conversion routines.

 */

#define JPEG_INTERNALS

#include "jinclude.h"

#include "jpeglib.h"

#include "jsimd.h"

/* Private subobject */

typedef struct {

  struct jpeg_color_converter pub; /* public fields */

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

  JLONG *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     ((JLONG)CENTERJSAMPLE << SCALEBITS)

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

#define FIX(x)          ((JLONG)((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))

/* 12-bit samples use a 16-bit data type, so it is possible to pass

 * out-of-range sample values (< 0 or > 4095) to jpeg_write_scanlines().

 * Thus, we mask the incoming 12-bit samples to guard against overrunning

 * or underrunning the conversion tables.

 */

#if BITS_IN_JSAMPLE == 12

#define RANGE_LIMIT(value)  ((value) & 0xFFF)

#else

#define RANGE_LIMIT(value)  (value)

#endif

/* Include inline routines for colorspace extensions */

#include "jccolext.c"

#undef RGB_RED

#undef RGB_GREEN

#undef RGB_BLUE

#undef RGB_PIXELSIZE

#define RGB_RED  EXT_RGB_RED

#define RGB_GREEN  EXT_RGB_GREEN

#define RGB_BLUE  EXT_RGB_BLUE

#define RGB_PIXELSIZE  EXT_RGB_PIXELSIZE

#define rgb_ycc_convert_internal  extrgb_ycc_convert_internal

#define rgb_gray_convert_internal  extrgb_gray_convert_internal

#define rgb_rgb_convert_internal  extrgb_rgb_convert_internal

#include "jccolext.c"

#undef RGB_RED

#undef RGB_GREEN

#undef RGB_BLUE

#undef RGB_PIXELSIZE

#undef rgb_ycc_convert_internal

#undef rgb_gray_convert_internal

#undef rgb_rgb_convert_internal

#define RGB_RED  EXT_RGBX_RED

#define RGB_GREEN  EXT_RGBX_GREEN

#define RGB_BLUE  EXT_RGBX_BLUE

#define RGB_PIXELSIZE  EXT_RGBX_PIXELSIZE

#define rgb_ycc_convert_internal  extrgbx_ycc_convert_internal

#define rgb_gray_convert_internal  extrgbx_gray_convert_internal

#define rgb_rgb_convert_internal  extrgbx_rgb_convert_internal

#include "jccolext.c"

#undef RGB_RED

#undef RGB_GREEN

#undef RGB_BLUE

#undef RGB_PIXELSIZE

#undef rgb_ycc_convert_internal

#undef rgb_gray_convert_internal

#undef rgb_rgb_convert_internal

#define RGB_RED  EXT_BGR_RED

#define RGB_GREEN  EXT_BGR_GREEN

#define RGB_BLUE  EXT_BGR_BLUE

#define RGB_PIXELSIZE  EXT_BGR_PIXELSIZE

#define rgb_ycc_convert_internal  extbgr_ycc_convert_internal

#define rgb_gray_convert_internal  extbgr_gray_convert_internal

#define rgb_rgb_convert_internal  extbgr_rgb_convert_internal

#include "jccolext.c"

#undef RGB_RED

#undef RGB_GREEN

#undef RGB_BLUE

#undef RGB_PIXELSIZE

#undef rgb_ycc_convert_internal

#undef rgb_gray_convert_internal

#undef rgb_rgb_convert_internal

#define RGB_RED  EXT_BGRX_RED

#define RGB_GREEN  EXT_BGRX_GREEN

#define RGB_BLUE  EXT_BGRX_BLUE

#define RGB_PIXELSIZE  EXT_BGRX_PIXELSIZE

#define rgb_ycc_convert_internal  extbgrx_ycc_convert_internal

#define rgb_gray_convert_internal  extbgrx_gray_convert_internal

#define rgb_rgb_convert_internal  extbgrx_rgb_convert_internal

#include "jccolext.c"

#undef RGB_RED

#undef RGB_GREEN

#undef RGB_BLUE

#undef RGB_PIXELSIZE

#undef rgb_ycc_convert_internal

#undef rgb_gray_convert_internal

#undef rgb_rgb_convert_internal

#define RGB_RED  EXT_XBGR_RED

#define RGB_GREEN  EXT_XBGR_GREEN

#define RGB_BLUE  EXT_XBGR_BLUE

#define RGB_PIXELSIZE  EXT_XBGR_PIXELSIZE

#define rgb_ycc_convert_internal  extxbgr_ycc_convert_internal

#define rgb_gray_convert_internal  extxbgr_gray_convert_internal

#define rgb_rgb_convert_internal  extxbgr_rgb_convert_internal

#include "jccolext.c"

#undef RGB_RED

#undef RGB_GREEN

#undef RGB_BLUE

#undef RGB_PIXELSIZE

#undef rgb_ycc_convert_internal

#undef rgb_gray_convert_internal

#undef rgb_rgb_convert_internal

#define RGB_RED  EXT_XRGB_RED

#define RGB_GREEN  EXT_XRGB_GREEN

#define RGB_BLUE  EXT_XRGB_BLUE

#define RGB_PIXELSIZE  EXT_XRGB_PIXELSIZE

#define rgb_ycc_convert_internal  extxrgb_ycc_convert_internal

#define rgb_gray_convert_internal  extxrgb_gray_convert_internal

#define rgb_rgb_convert_internal  extxrgb_rgb_convert_internal

#include "jccolext.c"

#undef RGB_RED

#undef RGB_GREEN

#undef RGB_BLUE

#undef RGB_PIXELSIZE

#undef rgb_ycc_convert_internal

#undef rgb_gray_convert_internal

#undef rgb_rgb_convert_internal

/*

 * Initialize for RGB->YCC colorspace conversion.

 */

METHODDEF(void)

rgb_ycc_start(j_compress_ptr cinfo)

{

  my_cconvert_ptr cconvert = (my_cconvert_ptr)cinfo->cconvert;

  JLONG *rgb_ycc_tab;

  JLONG i;

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

  cconvert->rgb_ycc_tab = rgb_ycc_tab = (JLONG *)

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

                                (TABLE_SIZE * sizeof(JLONG)));

  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.

 */

METHODDEF(void)

rgb_ycc_convert(j_compress_ptr cinfo, JSAMPARRAY input_buf,

                JSAMPIMAGE output_buf, JDIMENSION output_row, int num_rows)

{

  switch (cinfo->in_color_space) {

  case JCS_EXT_RGB:

    extrgb_ycc_convert_internal(cinfo, input_buf, output_buf, output_row,

                                num_rows);

    break;

  case JCS_EXT_RGBX:

  case JCS_EXT_RGBA:

    extrgbx_ycc_convert_internal(cinfo, input_buf, output_buf, output_row,

                                 num_rows);

    break;

  case JCS_EXT_BGR:

    extbgr_ycc_convert_internal(cinfo, input_buf, output_buf, output_row,

                                num_rows);

    break;

  case JCS_EXT_BGRX:

  case JCS_EXT_BGRA:

    extbgrx_ycc_convert_internal(cinfo, input_buf, output_buf, output_row,

                                 num_rows);

    break;

  case JCS_EXT_XBGR:

  case JCS_EXT_ABGR:

    extxbgr_ycc_convert_internal(cinfo, input_buf, output_buf, output_row,

                                 num_rows);

    break;

  case JCS_EXT_XRGB:

  case JCS_EXT_ARGB:

    extxrgb_ycc_convert_internal(cinfo, input_buf, output_buf, output_row,

                                 num_rows);

    break;

  default:

    rgb_ycc_convert_internal(cinfo, input_buf, output_buf, output_row,

                             num_rows);

    break;

  }

}

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

/*

 * Convert some rows of samples to the JPEG colorspace.

 */

METHODDEF(void)

rgb_gray_convert(j_compress_ptr cinfo, JSAMPARRAY input_buf,

                 JSAMPIMAGE output_buf, JDIMENSION output_row, int num_rows)

{

  switch (cinfo->in_color_space) {

  case JCS_EXT_RGB:

    extrgb_gray_convert_internal(cinfo, input_buf, output_buf, output_row,

                                 num_rows);

    break;

  case JCS_EXT_RGBX:

  case JCS_EXT_RGBA:

    extrgbx_gray_convert_internal(cinfo, input_buf, output_buf, output_row,

                                  num_rows);

    break;

  case JCS_EXT_BGR:

    extbgr_gray_convert_internal(cinfo, input_buf, output_buf, output_row,

                                 num_rows);

    break;

  case JCS_EXT_BGRX:

  case JCS_EXT_BGRA:

    extbgrx_gray_convert_internal(cinfo, input_buf, output_buf, output_row,

                                  num_rows);

    break;

  case JCS_EXT_XBGR:

  case JCS_EXT_ABGR:

    extxbgr_gray_convert_internal(cinfo, input_buf, output_buf, output_row,

                                  num_rows);

    break;

  case JCS_EXT_XRGB:

  case JCS_EXT_ARGB:

    extxrgb_gray_convert_internal(cinfo, input_buf, output_buf, output_row,

                                  num_rows);

    break;

  default:

    rgb_gray_convert_internal(cinfo, input_buf, output_buf, output_row,

                              num_rows);

    break;

  }

}

/*

 * Extended RGB to plain RGB conversion

 */

METHODDEF(void)

rgb_rgb_convert(j_compress_ptr cinfo, JSAMPARRAY input_buf,

                JSAMPIMAGE output_buf, JDIMENSION output_row, int num_rows)

{

  switch (cinfo->in_color_space) {

  case JCS_EXT_RGB:

    extrgb_rgb_convert_internal(cinfo, input_buf, output_buf, output_row,

                                num_rows);

    break;

  case JCS_EXT_RGBX:

  case JCS_EXT_RGBA:

    extrgbx_rgb_convert_internal(cinfo, input_buf, output_buf, output_row,

                                 num_rows);

    break;

  case JCS_EXT_BGR:

    extbgr_rgb_convert_internal(cinfo, input_buf, output_buf, output_row,

                                num_rows);

    break;

  case JCS_EXT_BGRX:

  case JCS_EXT_BGRA:

    extbgrx_rgb_convert_internal(cinfo, input_buf, output_buf, output_row,

                                 num_rows);

    break;

  case JCS_EXT_XBGR:

  case JCS_EXT_ABGR:

    extxbgr_rgb_convert_internal(cinfo, input_buf, output_buf, output_row,

                                 num_rows);

    break;

  case JCS_EXT_XRGB:

  case JCS_EXT_ARGB:

    extxrgb_rgb_convert_internal(cinfo, input_buf, output_buf, output_row,

                                 num_rows);

    break;

  default:

    rgb_rgb_convert_internal(cinfo, input_buf, output_buf, output_row,

                             num_rows);

    break;

  }

}

/*

 * 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 JLONG *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 - RANGE_LIMIT(inptr[0]);

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

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

      /* K passes through as-is */

      outptr3[col] = inptr[3];

      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];

      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, outptr0, outptr1, outptr2, outptr3;

  register JDIMENSION col;

  register int ci;

  int nc = cinfo->num_components;

  JDIMENSION num_cols = cinfo->image_width;

  if (nc == 3) {

    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++) {

        outptr0[col] = *inptr++;

        outptr1[col] = *inptr++;

        outptr2[col] = *inptr++;

      }

    }

  } else if (nc == 4) {

    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++) {

        outptr0[col] = *inptr++;

        outptr1[col] = *inptr++;

        outptr2[col] = *inptr++;

        outptr3[col] = *inptr++;

      }

    }

  } else {

    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];

          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:

  case JCS_EXT_RGB:

  case JCS_EXT_RGBX:

  case JCS_EXT_BGR:

  case JCS_EXT_BGRX:

  case JCS_EXT_XBGR:

  case JCS_EXT_XRGB:

  case JCS_EXT_RGBA:

  case JCS_EXT_BGRA:

  case JCS_EXT_ABGR:

  case JCS_EXT_ARGB:

    if (cinfo->input_components != rgb_pixelsize[cinfo->in_color_space])

      ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);

    break;

  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 ||

             cinfo->in_color_space == JCS_EXT_RGB ||

             cinfo->in_color_space == JCS_EXT_RGBX ||

             cinfo->in_color_space == JCS_EXT_BGR ||

             cinfo->in_color_space == JCS_EXT_BGRX ||

             cinfo->in_color_space == JCS_EXT_XBGR ||

             cinfo->in_color_space == JCS_EXT_XRGB ||

             cinfo->in_color_space == JCS_EXT_RGBA ||

             cinfo->in_color_space == JCS_EXT_BGRA ||

             cinfo->in_color_space == JCS_EXT_ABGR ||

             cinfo->in_color_space == JCS_EXT_ARGB) {

      if (jsimd_can_rgb_gray())

        cconvert->pub.color_convert = jsimd_rgb_gray_convert;

      else {

        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 (rgb_red[cinfo->in_color_space] == 0 &&

        rgb_green[cinfo->in_color_space] == 1 &&

        rgb_blue[cinfo->in_color_space] == 2 &&

        rgb_pixelsize[cinfo->in_color_space] == 3) {

#if defined(__mips__)

      if (jsimd_c_can_null_convert())

        cconvert->pub.color_convert = jsimd_c_null_convert;

      else

#endif

        cconvert->pub.color_convert = null_convert;

    } else if (cinfo->in_color_space == JCS_RGB ||

               cinfo->in_color_space == JCS_EXT_RGB ||

               cinfo->in_color_space == JCS_EXT_RGBX ||

               cinfo->in_color_space == JCS_EXT_BGR ||

               cinfo->in_color_space == JCS_EXT_BGRX ||

               cinfo->in_color_space == JCS_EXT_XBGR ||

               cinfo->in_color_space == JCS_EXT_XRGB ||

               cinfo->in_color_space == JCS_EXT_RGBA ||

               cinfo->in_color_space == JCS_EXT_BGRA ||

               cinfo->in_color_space == JCS_EXT_ABGR ||

               cinfo->in_color_space == JCS_EXT_ARGB)

      cconvert->pub.color_convert = rgb_rgb_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 ||

        cinfo->in_color_space == JCS_EXT_RGB ||

        cinfo->in_color_space == JCS_EXT_RGBX ||

        cinfo->in_color_space == JCS_EXT_BGR ||

        cinfo->in_color_space == JCS_EXT_BGRX ||

        cinfo->in_color_space == JCS_EXT_XBGR ||

        cinfo->in_color_space == JCS_EXT_XRGB ||

        cinfo->in_color_space == JCS_EXT_RGBA ||

        cinfo->in_color_space == JCS_EXT_BGRA ||

        cinfo->in_color_space == JCS_EXT_ABGR ||

        cinfo->in_color_space == JCS_EXT_ARGB) {

      if (jsimd_can_rgb_ycc())

        cconvert->pub.color_convert = jsimd_rgb_ycc_convert;

      else {

        cconvert->pub.start_pass = rgb_ycc_start;

        cconvert->pub.color_convert = rgb_ycc_convert;

      }

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

#if defined(__mips__)

      if (jsimd_c_can_null_convert())

        cconvert->pub.color_convert = jsimd_c_null_convert;

      else

#endif

        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) {

#if defined(__mips__)

      if (jsimd_c_can_null_convert())

        cconvert->pub.color_convert = jsimd_c_null_convert;

      else

#endif

        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) {

#if defined(__mips__)

      if (jsimd_c_can_null_convert())

        cconvert->pub.color_convert = jsimd_c_null_convert;

      else

#endif

        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);

#if defined(__mips__)

    if (jsimd_c_can_null_convert())

      cconvert->pub.color_convert = jsimd_c_null_convert;

    else

#endif

      cconvert->pub.color_convert = null_convert;

    break;

  }

}