/*+
−
 * jquant1.c+
−
 *+
−
 * Copyright (C) 1991-1996, Thomas G. Lane.+
−
 * This file is part of the Independent JPEG Group's software.+
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 * For conditions of distribution and use, see the accompanying README file.+
−
 *+
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 * This file contains 1-pass color quantization (color mapping) routines.+
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 * These routines provide mapping to a fixed color map using equally spaced+
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 * color values.  Optional Floyd-Steinberg or ordered dithering is available.+
−
 */+
−
+
−
#define JPEG_INTERNALS+
−
#include "jinclude.h"+
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#include "jpeglib.h"+
−
+
−
#ifdef QUANT_1PASS_SUPPORTED+
−
+
−
+
−
/*+
−
 * The main purpose of 1-pass quantization is to provide a fast, if not very+
−
 * high quality, colormapped output capability.  A 2-pass quantizer usually+
−
 * gives better visual quality; however, for quantized grayscale output this+
−
 * quantizer is perfectly adequate.  Dithering is highly recommended with this+
−
 * quantizer, though you can turn it off if you really want to.+
−
 *+
−
 * In 1-pass quantization the colormap must be chosen in advance of seeing the+
−
 * image.  We use a map consisting of all combinations of Ncolors[i] color+
−
 * values for the i'th component.  The Ncolors[] values are chosen so that+
−
 * their product, the total number of colors, is no more than that requested.+
−
 * (In most cases, the product will be somewhat less.)+
−
 *+
−
 * Since the colormap is orthogonal, the representative value for each color+
−
 * component can be determined without considering the other components;+
−
 * then these indexes can be combined into a colormap index by a standard+
−
 * N-dimensional-array-subscript calculation.  Most of the arithmetic involved+
−
 * can be precalculated and stored in the lookup table colorindex[].+
−
 * colorindex[i][j] maps pixel value j in component i to the nearest+
−
 * representative value (grid plane) for that component; this index is+
−
 * multiplied by the array stride for component i, so that the+
−
 * index of the colormap entry closest to a given pixel value is just+
−
 *    sum( colorindex[component-number][pixel-component-value] )+
−
 * Aside from being fast, this scheme allows for variable spacing between+
−
 * representative values with no additional lookup cost.+
−
 *+
−
 * If gamma correction has been applied in color conversion, it might be wise+
−
 * to adjust the color grid spacing so that the representative colors are+
−
 * equidistant in linear space.  At this writing, gamma correction is not+
−
 * implemented by jdcolor, so nothing is done here.+
−
 */+
−
+
−
+
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/* Declarations for ordered dithering.+
−
 *+
−
 * We use a standard 16x16 ordered dither array.  The basic concept of ordered+
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 * dithering is described in many references, for instance Dale Schumacher's+
−
 * chapter II.2 of Graphics Gems II (James Arvo, ed. Academic Press, 1991).+
−
 * In place of Schumacher's comparisons against a "threshold" value, we add a+
−
 * "dither" value to the input pixel and then round the result to the nearest+
−
 * output value.  The dither value is equivalent to (0.5 - threshold) times+
−
 * the distance between output values.  For ordered dithering, we assume that+
−
 * the output colors are equally spaced; if not, results will probably be+
−
 * worse, since the dither may be too much or too little at a given point.+
−
 *+
−
 * The normal calculation would be to form pixel value + dither, range-limit+
−
 * this to 0..MAXJSAMPLE, and then index into the colorindex table as usual.+
−
 * We can skip the separate range-limiting step by extending the colorindex+
−
 * table in both directions.+
−
 */+
−
+
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#define ODITHER_SIZE  16	/* dimension of dither matrix */+
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/* NB: if ODITHER_SIZE is not a power of 2, ODITHER_MASK uses will break */+
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#define ODITHER_CELLS (ODITHER_SIZE*ODITHER_SIZE)	/* # cells in matrix */+
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#define ODITHER_MASK  (ODITHER_SIZE-1) /* mask for wrapping around counters */+
−
+
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typedef int ODITHER_MATRIX[ODITHER_SIZE][ODITHER_SIZE];+
−
typedef int (*ODITHER_MATRIX_PTR)[ODITHER_SIZE];+
−
+
−
static const UINT8 base_dither_matrix[ODITHER_SIZE][ODITHER_SIZE] = {+
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  /* Bayer's order-4 dither array.  Generated by the code given in+
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   * Stephen Hawley's article "Ordered Dithering" in Graphics Gems I.+
−
   * The values in this array must range from 0 to ODITHER_CELLS-1.+
−
   */+
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  {   0,192, 48,240, 12,204, 60,252,  3,195, 51,243, 15,207, 63,255 },+
−
  { 128, 64,176,112,140, 76,188,124,131, 67,179,115,143, 79,191,127 },+
−
  {  32,224, 16,208, 44,236, 28,220, 35,227, 19,211, 47,239, 31,223 },+
−
  { 160, 96,144, 80,172,108,156, 92,163, 99,147, 83,175,111,159, 95 },+
−
  {   8,200, 56,248,  4,196, 52,244, 11,203, 59,251,  7,199, 55,247 },+
−
  { 136, 72,184,120,132, 68,180,116,139, 75,187,123,135, 71,183,119 },+
−
  {  40,232, 24,216, 36,228, 20,212, 43,235, 27,219, 39,231, 23,215 },+
−
  { 168,104,152, 88,164,100,148, 84,171,107,155, 91,167,103,151, 87 },+
−
  {   2,194, 50,242, 14,206, 62,254,  1,193, 49,241, 13,205, 61,253 },+
−
  { 130, 66,178,114,142, 78,190,126,129, 65,177,113,141, 77,189,125 },+
−
  {  34,226, 18,210, 46,238, 30,222, 33,225, 17,209, 45,237, 29,221 },+
−
  { 162, 98,146, 82,174,110,158, 94,161, 97,145, 81,173,109,157, 93 },+
−
  {  10,202, 58,250,  6,198, 54,246,  9,201, 57,249,  5,197, 53,245 },+
−
  { 138, 74,186,122,134, 70,182,118,137, 73,185,121,133, 69,181,117 },+
−
  {  42,234, 26,218, 38,230, 22,214, 41,233, 25,217, 37,229, 21,213 },+
−
  { 170,106,154, 90,166,102,150, 86,169,105,153, 89,165,101,149, 85 }+
−
};+
−
+
−
+
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/* Declarations for Floyd-Steinberg dithering.+
−
 *+
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 * Errors are accumulated into the array fserrors[], at a resolution of+
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 * 1/16th of a pixel count.  The error at a given pixel is propagated+
−
 * to its not-yet-processed neighbors using the standard F-S fractions,+
−
 *		...	(here)	7/16+
−
 *		3/16	5/16	1/16+
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 * We work left-to-right on even rows, right-to-left on odd rows.+
−
 *+
−
 * We can get away with a single array (holding one row's worth of errors)+
−
 * by using it to store the current row's errors at pixel columns not yet+
−
 * processed, but the next row's errors at columns already processed.  We+
−
 * need only a few extra variables to hold the errors immediately around the+
−
 * current column.  (If we are lucky, those variables are in registers, but+
−
 * even if not, they're probably cheaper to access than array elements are.)+
−
 *+
−
 * The fserrors[] array is indexed [component#][position].+
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 * We provide (#columns + 2) entries per component; the extra entry at each+
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 * end saves us from special-casing the first and last pixels.+
−
 *+
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 * Note: on a wide image, we might not have enough room in a PC's near data+
−
 * segment to hold the error array; so it is allocated with alloc_large.+
−
 */+
−
+
−
#if BITS_IN_JSAMPLE == 8+
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typedef INT16 FSERROR;		/* 16 bits should be enough */+
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typedef int LOCFSERROR;		/* use 'int' for calculation temps */+
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#else+
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typedef INT32 FSERROR;		/* may need more than 16 bits */+
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typedef INT32 LOCFSERROR;	/* be sure calculation temps are big enough */+
−
#endif+
−
+
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typedef FSERROR FAR *FSERRPTR;	/* pointer to error array (in FAR storage!) */+
−
+
−
+
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/* Private subobject */+
−
+
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#define MAX_Q_COMPS 4		/* max components I can handle */+
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+
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typedef struct {+
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  struct jpeg_color_quantizer pub; /* public fields */+
−
+
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  /* Initially allocated colormap is saved here */+
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  JSAMPARRAY sv_colormap;	/* The color map as a 2-D pixel array */+
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  int sv_actual;		/* number of entries in use */+
−
+
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  JSAMPARRAY colorindex;	/* Precomputed mapping for speed */+
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  /* colorindex[i][j] = index of color closest to pixel value j in component i,+
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   * premultiplied as described above.  Since colormap indexes must fit into+
−
   * JSAMPLEs, the entries of this array will too.+
−
   */+
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  boolean is_padded;		/* is the colorindex padded for odither? */+
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+
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  int Ncolors[MAX_Q_COMPS];	/* # of values alloced to each component */+
−
+
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  /* Variables for ordered dithering */+
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  int row_index;		/* cur row's vertical index in dither matrix */+
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  ODITHER_MATRIX_PTR odither[MAX_Q_COMPS]; /* one dither array per component */+
−
+
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  /* Variables for Floyd-Steinberg dithering */+
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  FSERRPTR fserrors[MAX_Q_COMPS]; /* accumulated errors */+
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  boolean on_odd_row;		/* flag to remember which row we are on */+
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} my_cquantizer;+
−
+
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typedef my_cquantizer * my_cquantize_ptr;+
−
+
−
+
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/*+
−
 * Policy-making subroutines for create_colormap and create_colorindex.+
−
 * These routines determine the colormap to be used.  The rest of the module+
−
 * only assumes that the colormap is orthogonal.+
−
 *+
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 *  * select_ncolors decides how to divvy up the available colors+
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 *    among the components.+
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 *  * output_value defines the set of representative values for a component.+
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 *  * largest_input_value defines the mapping from input values to+
−
 *    representative values for a component.+
−
 * Note that the latter two routines may impose different policies for+
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 * different components, though this is not currently done.+
−
 */+
−
+
−
+
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LOCAL(int)+
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select_ncolors (j_decompress_ptr cinfo, int Ncolors[])+
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/* Determine allocation of desired colors to components, */+
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/* and fill in Ncolors[] array to indicate choice. */+
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/* Return value is total number of colors (product of Ncolors[] values). */+
−
{+
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  int nc = cinfo->out_color_components; /* number of color components */+
−
  int max_colors = cinfo->desired_number_of_colors;+
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  int total_colors, iroot, i, j;+
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  boolean changed;+
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  long temp;+
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  static const int RGB_order[3] = { RGB_GREEN, RGB_RED, RGB_BLUE };+
−
+
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  /* We can allocate at least the nc'th root of max_colors per component. */+
−
  /* Compute floor(nc'th root of max_colors). */+
−
  iroot = 1;+
−
  do {+
−
    iroot++;+
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    temp = iroot;		/* set temp = iroot ** nc */+
−
    for (i = 1; i < nc; i++)+
−
      temp *= iroot;+
−
  } while (temp <= (long) max_colors); /* repeat till iroot exceeds root */+
−
  iroot--;			/* now iroot = floor(root) */+
−
+
−
  /* Must have at least 2 color values per component */+
−
  if (iroot < 2)+
−
    ERREXIT1(cinfo, JERR_QUANT_FEW_COLORS, (int) temp);+
−
+
−
  /* Initialize to iroot color values for each component */+
−
  total_colors = 1;+
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  for (i = 0; i < nc; i++) {+
−
    Ncolors[i] = iroot;+
−
    total_colors *= iroot;+
−
  }+
−
  /* We may be able to increment the count for one or more components without+
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   * exceeding max_colors, though we know not all can be incremented.+
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   * Sometimes, the first component can be incremented more than once!+
−
   * (Example: for 16 colors, we start at 2*2*2, go to 3*2*2, then 4*2*2.)+
−
   * In RGB colorspace, try to increment G first, then R, then B.+
−
   */+
−
  do {+
−
    changed = FALSE;+
−
    for (i = 0; i < nc; i++) {+
−
      j = (cinfo->out_color_space == JCS_RGB ? RGB_order[i] : i);+
−
      /* calculate new total_colors if Ncolors[j] is incremented */+
−
      temp = total_colors / Ncolors[j];+
−
      temp *= Ncolors[j]+1;	/* done in long arith to avoid oflo */+
−
      if (temp > (long) max_colors)+
−
	break;			/* won't fit, done with this pass */+
−
      Ncolors[j]++;		/* OK, apply the increment */+
−
      total_colors = (int) temp;+
−
      changed = TRUE;+
−
    }+
−
  } while (changed);+
−
+
−
  return total_colors;+
−
}+
−
+
−
+
−
LOCAL(int)+
−
output_value (j_decompress_ptr cinfo, int ci, int j, int maxj)+
−
/* Return j'th output value, where j will range from 0 to maxj */+
−
/* The output values must fall in 0..MAXJSAMPLE in increasing order */+
−
{+
−
  /* We always provide values 0 and MAXJSAMPLE for each component;+
−
   * any additional values are equally spaced between these limits.+
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   * (Forcing the upper and lower values to the limits ensures that+
−
   * dithering can't produce a color outside the selected gamut.)+
−
   */+
−
  return (int) (((INT32) j * MAXJSAMPLE + maxj/2) / maxj);+
−
}+
−
+
−
+
−
LOCAL(int)+
−
largest_input_value (j_decompress_ptr cinfo, int ci, int j, int maxj)+
−
/* Return largest input value that should map to j'th output value */+
−
/* Must have largest(j=0) >= 0, and largest(j=maxj) >= MAXJSAMPLE */+
−
{+
−
  /* Breakpoints are halfway between values returned by output_value */+
−
  return (int) (((INT32) (2*j + 1) * MAXJSAMPLE + maxj) / (2*maxj));+
−
}+
−
+
−
+
−
/*+
−
 * Create the colormap.+
−
 */+
−
+
−
LOCAL(void)+
−
create_colormap (j_decompress_ptr cinfo)+
−
{+
−
  my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;+
−
  JSAMPARRAY colormap;		/* Created colormap */+
−
  int total_colors;		/* Number of distinct output colors */+
−
  int i,j,k, nci, blksize, blkdist, ptr, val;+
−
+
−
  /* Select number of colors for each component */+
−
  total_colors = select_ncolors(cinfo, cquantize->Ncolors);+
−
+
−
  /* Report selected color counts */+
−
  if (cinfo->out_color_components == 3)+
−
    TRACEMS4(cinfo, 1, JTRC_QUANT_3_NCOLORS,+
−
	     total_colors, cquantize->Ncolors[0],+
−
	     cquantize->Ncolors[1], cquantize->Ncolors[2]);+
−
  else+
−
    TRACEMS1(cinfo, 1, JTRC_QUANT_NCOLORS, total_colors);+
−
+
−
  /* Allocate and fill in the colormap. */+
−
  /* The colors are ordered in the map in standard row-major order, */+
−
  /* i.e. rightmost (highest-indexed) color changes most rapidly. */+
−
+
−
  colormap = (*cinfo->mem->alloc_sarray)+
−
    ((j_common_ptr) cinfo, JPOOL_IMAGE,+
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     (JDIMENSION) total_colors, (JDIMENSION) cinfo->out_color_components);+
−
+
−
  /* blksize is number of adjacent repeated entries for a component */+
−
  /* blkdist is distance between groups of identical entries for a component */+
−
  blkdist = total_colors;+
−
+
−
  for (i = 0; i < cinfo->out_color_components; i++) {+
−
    /* fill in colormap entries for i'th color component */+
−
    nci = cquantize->Ncolors[i]; /* # of distinct values for this color */+
−
    blksize = blkdist / nci;+
−
    for (j = 0; j < nci; j++) {+
−
      /* Compute j'th output value (out of nci) for component */+
−
      val = output_value(cinfo, i, j, nci-1);+
−
      /* Fill in all colormap entries that have this value of this component */+
−
      for (ptr = j * blksize; ptr < total_colors; ptr += blkdist) {+
−
	/* fill in blksize entries beginning at ptr */+
−
	for (k = 0; k < blksize; k++)+
−
	  colormap[i][ptr+k] = (JSAMPLE) val;+
−
      }+
−
    }+
−
    blkdist = blksize;		/* blksize of this color is blkdist of next */+
−
  }+
−
+
−
  /* Save the colormap in private storage,+
−
   * where it will survive color quantization mode changes.+
−
   */+
−
  cquantize->sv_colormap = colormap;+
−
  cquantize->sv_actual = total_colors;+
−
}+
−
+
−
+
−
/*+
−
 * Create the color index table.+
−
 */+
−
+
−
LOCAL(void)+
−
create_colorindex (j_decompress_ptr cinfo)+
−
{+
−
  my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;+
−
  JSAMPROW indexptr;+
−
  int i,j,k, nci, blksize, val, pad;+
−
+
−
  /* For ordered dither, we pad the color index tables by MAXJSAMPLE in+
−
   * each direction (input index values can be -MAXJSAMPLE .. 2*MAXJSAMPLE).+
−
   * This is not necessary in the other dithering modes.  However, we+
−
   * flag whether it was done in case user changes dithering mode.+
−
   */+
−
  if (cinfo->dither_mode == JDITHER_ORDERED) {+
−
    pad = MAXJSAMPLE*2;+
−
    cquantize->is_padded = TRUE;+
−
  } else {+
−
    pad = 0;+
−
    cquantize->is_padded = FALSE;+
−
  }+
−
+
−
  cquantize->colorindex = (*cinfo->mem->alloc_sarray)+
−
    ((j_common_ptr) cinfo, JPOOL_IMAGE,+
−
     (JDIMENSION) (MAXJSAMPLE+1 + pad),+
−
     (JDIMENSION) cinfo->out_color_components);+
−
+
−
  /* blksize is number of adjacent repeated entries for a component */+
−
  blksize = cquantize->sv_actual;+
−
+
−
  for (i = 0; i < cinfo->out_color_components; i++) {+
−
    /* fill in colorindex entries for i'th color component */+
−
    nci = cquantize->Ncolors[i]; /* # of distinct values for this color */+
−
    blksize = blksize / nci;+
−
+
−
    /* adjust colorindex pointers to provide padding at negative indexes. */+
−
    if (pad)+
−
      cquantize->colorindex[i] += MAXJSAMPLE;+
−
+
−
    /* in loop, val = index of current output value, */+
−
    /* and k = largest j that maps to current val */+
−
    indexptr = cquantize->colorindex[i];+
−
    val = 0;+
−
    k = largest_input_value(cinfo, i, 0, nci-1);+
−
    for (j = 0; j <= MAXJSAMPLE; j++) {+
−
      while (j > k)		/* advance val if past boundary */+
−
	k = largest_input_value(cinfo, i, ++val, nci-1);+
−
      /* premultiply so that no multiplication needed in main processing */+
−
      indexptr[j] = (JSAMPLE) (val * blksize);+
−
    }+
−
    /* Pad at both ends if necessary */+
−
    if (pad)+
−
      for (j = 1; j <= MAXJSAMPLE; j++) {+
−
	indexptr[-j] = indexptr[0];+
−
	indexptr[MAXJSAMPLE+j] = indexptr[MAXJSAMPLE];+
−
      }+
−
  }+
−
}+
−
+
−
+
−
/*+
−
 * Create an ordered-dither array for a component having ncolors+
−
 * distinct output values.+
−
 */+
−
+
−
LOCAL(ODITHER_MATRIX_PTR)+
−
make_odither_array (j_decompress_ptr cinfo, int ncolors)+
−
{+
−
  ODITHER_MATRIX_PTR odither;+
−
  int j,k;+
−
  INT32 num,den;+
−
+
−
  odither = (ODITHER_MATRIX_PTR)+
−
    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,+
−
				SIZEOF(ODITHER_MATRIX));+
−
  /* The inter-value distance for this color is MAXJSAMPLE/(ncolors-1).+
−
   * Hence the dither value for the matrix cell with fill order f+
−
   * (f=0..N-1) should be (N-1-2*f)/(2*N) * MAXJSAMPLE/(ncolors-1).+
−
   * On 16-bit-int machine, be careful to avoid overflow.+
−
   */+
−
  den = 2 * ODITHER_CELLS * ((INT32) (ncolors - 1));+
−
  for (j = 0; j < ODITHER_SIZE; j++) {+
−
    for (k = 0; k < ODITHER_SIZE; k++) {+
−
      num = ((INT32) (ODITHER_CELLS-1 - 2*((int)base_dither_matrix[j][k])))+
−
	    * MAXJSAMPLE;+
−
      /* Ensure round towards zero despite C's lack of consistency+
−
       * about rounding negative values in integer division...+
−
       */+
−
      odither[j][k] = (int) (num<0 ? -((-num)/den) : num/den);+
−
    }+
−
  }+
−
  return odither;+
−
}+
−
+
−
+
−
/*+
−
 * Create the ordered-dither tables.+
−
 * Components having the same number of representative colors may +
−
 * share a dither table.+
−
 */+
−
+
−
LOCAL(void)+
−
create_odither_tables (j_decompress_ptr cinfo)+
−
{+
−
  my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;+
−
  ODITHER_MATRIX_PTR odither;+
−
  int i, j, nci;+
−
+
−
  for (i = 0; i < cinfo->out_color_components; i++) {+
−
    nci = cquantize->Ncolors[i]; /* # of distinct values for this color */+
−
    odither = NULL;		/* search for matching prior component */+
−
    for (j = 0; j < i; j++) {+
−
      if (nci == cquantize->Ncolors[j]) {+
−
	odither = cquantize->odither[j];+
−
	break;+
−
      }+
−
    }+
−
    if (odither == NULL)	/* need a new table? */+
−
      odither = make_odither_array(cinfo, nci);+
−
    cquantize->odither[i] = odither;+
−
  }+
−
}+
−
+
−
+
−
/*+
−
 * Map some rows of pixels to the output colormapped representation.+
−
 */+
−
+
−
METHODDEF(void)+
−
color_quantize (j_decompress_ptr cinfo, JSAMPARRAY input_buf,+
−
		JSAMPARRAY output_buf, int num_rows)+
−
/* General case, no dithering */+
−
{+
−
  my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;+
−
  JSAMPARRAY colorindex = cquantize->colorindex;+
−
  register int pixcode, ci;+
−
  register JSAMPROW ptrin, ptrout;+
−
  int row;+
−
  JDIMENSION col;+
−
  JDIMENSION width = cinfo->output_width;+
−
  register int nc = cinfo->out_color_components;+
−
+
−
  for (row = 0; row < num_rows; row++) {+
−
    ptrin = input_buf[row];+
−
    ptrout = output_buf[row];+
−
    for (col = width; col > 0; col--) {+
−
      pixcode = 0;+
−
      for (ci = 0; ci < nc; ci++) {+
−
	pixcode += GETJSAMPLE(colorindex[ci][GETJSAMPLE(*ptrin++)]);+
−
      }+
−
      *ptrout++ = (JSAMPLE) pixcode;+
−
    }+
−
  }+
−
}+
−
+
−
+
−
METHODDEF(void)+
−
color_quantize3 (j_decompress_ptr cinfo, JSAMPARRAY input_buf,+
−
		 JSAMPARRAY output_buf, int num_rows)+
−
/* Fast path for out_color_components==3, no dithering */+
−
{+
−
  my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;+
−
  register int pixcode;+
−
  register JSAMPROW ptrin, ptrout;+
−
  JSAMPROW colorindex0 = cquantize->colorindex[0];+
−
  JSAMPROW colorindex1 = cquantize->colorindex[1];+
−
  JSAMPROW colorindex2 = cquantize->colorindex[2];+
−
  int row;+
−
  JDIMENSION col;+
−
  JDIMENSION width = cinfo->output_width;+
−
+
−
  for (row = 0; row < num_rows; row++) {+
−
    ptrin = input_buf[row];+
−
    ptrout = output_buf[row];+
−
    for (col = width; col > 0; col--) {+
−
      pixcode  = GETJSAMPLE(colorindex0[GETJSAMPLE(*ptrin++)]);+
−
      pixcode += GETJSAMPLE(colorindex1[GETJSAMPLE(*ptrin++)]);+
−
      pixcode += GETJSAMPLE(colorindex2[GETJSAMPLE(*ptrin++)]);+
−
      *ptrout++ = (JSAMPLE) pixcode;+
−
    }+
−
  }+
−
}+
−
+
−
+
−
METHODDEF(void)+
−
quantize_ord_dither (j_decompress_ptr cinfo, JSAMPARRAY input_buf,+
−
		     JSAMPARRAY output_buf, int num_rows)+
−
/* General case, with ordered dithering */+
−
{+
−
  my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;+
−
  register JSAMPROW input_ptr;+
−
  register JSAMPROW output_ptr;+
−
  JSAMPROW colorindex_ci;+
−
  int * dither;			/* points to active row of dither matrix */+
−
  int row_index, col_index;	/* current indexes into dither matrix */+
−
  int nc = cinfo->out_color_components;+
−
  int ci;+
−
  int row;+
−
  JDIMENSION col;+
−
  JDIMENSION width = cinfo->output_width;+
−
+
−
  for (row = 0; row < num_rows; row++) {+
−
    /* Initialize output values to 0 so can process components separately */+
−
    jzero_far((void FAR *) output_buf[row],+
−
	      (size_t) (width * SIZEOF(JSAMPLE)));+
−
    row_index = cquantize->row_index;+
−
    for (ci = 0; ci < nc; ci++) {+
−
      input_ptr = input_buf[row] + ci;+
−
      output_ptr = output_buf[row];+
−
      colorindex_ci = cquantize->colorindex[ci];+
−
      dither = cquantize->odither[ci][row_index];+
−
      col_index = 0;+
−
+
−
      for (col = width; col > 0; col--) {+
−
	/* Form pixel value + dither, range-limit to 0..MAXJSAMPLE,+
−
	 * select output value, accumulate into output code for this pixel.+
−
	 * Range-limiting need not be done explicitly, as we have extended+
−
	 * the colorindex table to produce the right answers for out-of-range+
−
	 * inputs.  The maximum dither is +- MAXJSAMPLE; this sets the+
−
	 * required amount of padding.+
−
	 */+
−
	*output_ptr += colorindex_ci[GETJSAMPLE(*input_ptr)+dither[col_index]];+
−
	input_ptr += nc;+
−
	output_ptr++;+
−
	col_index = (col_index + 1) & ODITHER_MASK;+
−
      }+
−
    }+
−
    /* Advance row index for next row */+
−
    row_index = (row_index + 1) & ODITHER_MASK;+
−
    cquantize->row_index = row_index;+
−
  }+
−
}+
−
+
−
+
−
METHODDEF(void)+
−
quantize3_ord_dither (j_decompress_ptr cinfo, JSAMPARRAY input_buf,+
−
		      JSAMPARRAY output_buf, int num_rows)+
−
/* Fast path for out_color_components==3, with ordered dithering */+
−
{+
−
  my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;+
−
  register int pixcode;+
−
  register JSAMPROW input_ptr;+
−
  register JSAMPROW output_ptr;+
−
  JSAMPROW colorindex0 = cquantize->colorindex[0];+
−
  JSAMPROW colorindex1 = cquantize->colorindex[1];+
−
  JSAMPROW colorindex2 = cquantize->colorindex[2];+
−
  int * dither0;		/* points to active row of dither matrix */+
−
  int * dither1;+
−
  int * dither2;+
−
  int row_index, col_index;	/* current indexes into dither matrix */+
−
  int row;+
−
  JDIMENSION col;+
−
  JDIMENSION width = cinfo->output_width;+
−
+
−
  for (row = 0; row < num_rows; row++) {+
−
    row_index = cquantize->row_index;+
−
    input_ptr = input_buf[row];+
−
    output_ptr = output_buf[row];+
−
    dither0 = cquantize->odither[0][row_index];+
−
    dither1 = cquantize->odither[1][row_index];+
−
    dither2 = cquantize->odither[2][row_index];+
−
    col_index = 0;+
−
+
−
    for (col = width; col > 0; col--) {+
−
      pixcode  = GETJSAMPLE(colorindex0[GETJSAMPLE(*input_ptr++) ++
−
					dither0[col_index]]);+
−
      pixcode += GETJSAMPLE(colorindex1[GETJSAMPLE(*input_ptr++) ++
−
					dither1[col_index]]);+
−
      pixcode += GETJSAMPLE(colorindex2[GETJSAMPLE(*input_ptr++) ++
−
					dither2[col_index]]);+
−
      *output_ptr++ = (JSAMPLE) pixcode;+
−
      col_index = (col_index + 1) & ODITHER_MASK;+
−
    }+
−
    row_index = (row_index + 1) & ODITHER_MASK;+
−
    cquantize->row_index = row_index;+
−
  }+
−
}+
−
+
−
+
−
METHODDEF(void)+
−
quantize_fs_dither (j_decompress_ptr cinfo, JSAMPARRAY input_buf,+
−
		    JSAMPARRAY output_buf, int num_rows)+
−
/* General case, with Floyd-Steinberg dithering */+
−
{+
−
  my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;+
−
  register LOCFSERROR cur;	/* current error or pixel value */+
−
  LOCFSERROR belowerr;		/* error for pixel below cur */+
−
  LOCFSERROR bpreverr;		/* error for below/prev col */+
−
  LOCFSERROR bnexterr;		/* error for below/next col */+
−
  LOCFSERROR delta;+
−
  register FSERRPTR errorptr;	/* => fserrors[] at column before current */+
−
  register JSAMPROW input_ptr;+
−
  register JSAMPROW output_ptr;+
−
  JSAMPROW colorindex_ci;+
−
  JSAMPROW colormap_ci;+
−
  int pixcode;+
−
  int nc = cinfo->out_color_components;+
−
  int dir;			/* 1 for left-to-right, -1 for right-to-left */+
−
  int dirnc;			/* dir * nc */+
−
  int ci;+
−
  int row;+
−
  JDIMENSION col;+
−
  JDIMENSION width = cinfo->output_width;+
−
  JSAMPLE *range_limit = cinfo->sample_range_limit;+
−
  SHIFT_TEMPS+
−
+
−
  for (row = 0; row < num_rows; row++) {+
−
    /* Initialize output values to 0 so can process components separately */+
−
    jzero_far((void FAR *) output_buf[row],+
−
	      (size_t) (width * SIZEOF(JSAMPLE)));+
−
    for (ci = 0; ci < nc; ci++) {+
−
      input_ptr = input_buf[row] + ci;+
−
      output_ptr = output_buf[row];+
−
      if (cquantize->on_odd_row) {+
−
	/* work right to left in this row */+
−
	input_ptr += (width-1) * nc; /* so point to rightmost pixel */+
−
	output_ptr += width-1;+
−
	dir = -1;+
−
	dirnc = -nc;+
−
	errorptr = cquantize->fserrors[ci] + (width+1); /* => entry after last column */+
−
      } else {+
−
	/* work left to right in this row */+
−
	dir = 1;+
−
	dirnc = nc;+
−
	errorptr = cquantize->fserrors[ci]; /* => entry before first column */+
−
      }+
−
      colorindex_ci = cquantize->colorindex[ci];+
−
      colormap_ci = cquantize->sv_colormap[ci];+
−
      /* Preset error values: no error propagated to first pixel from left */+
−
      cur = 0;+
−
      /* and no error propagated to row below yet */+
−
      belowerr = bpreverr = 0;+
−
+
−
      for (col = width; col > 0; col--) {+
−
	/* cur holds the error propagated from the previous pixel on the+
−
	 * current line.  Add the error propagated from the previous line+
−
	 * to form the complete error correction term for this pixel, and+
−
	 * round the error term (which is expressed * 16) to an integer.+
−
	 * RIGHT_SHIFT rounds towards minus infinity, so adding 8 is correct+
−
	 * for either sign of the error value.+
−
	 * Note: errorptr points to *previous* column's array entry.+
−
	 */+
−
	cur = RIGHT_SHIFT(cur + errorptr[dir] + 8, 4);+
−
	/* Form pixel value + error, and range-limit to 0..MAXJSAMPLE.+
−
	 * The maximum error is +- MAXJSAMPLE; this sets the required size+
−
	 * of the range_limit array.+
−
	 */+
−
	cur += GETJSAMPLE(*input_ptr);+
−
	cur = GETJSAMPLE(range_limit[cur]);+
−
	/* Select output value, accumulate into output code for this pixel */+
−
	pixcode = GETJSAMPLE(colorindex_ci[cur]);+
−
	*output_ptr += (JSAMPLE) pixcode;+
−
	/* Compute actual representation error at this pixel */+
−
	/* Note: we can do this even though we don't have the final */+
−
	/* pixel code, because the colormap is orthogonal. */+
−
	cur -= GETJSAMPLE(colormap_ci[pixcode]);+
−
	/* Compute error fractions to be propagated to adjacent pixels.+
−
	 * Add these into the running sums, and simultaneously shift the+
−
	 * next-line error sums left by 1 column.+
−
	 */+
−
	bnexterr = cur;+
−
	delta = cur * 2;+
−
	cur += delta;		/* form error * 3 */+
−
	errorptr[0] = (FSERROR) (bpreverr + cur);+
−
	cur += delta;		/* form error * 5 */+
−
	bpreverr = belowerr + cur;+
−
	belowerr = bnexterr;+
−
	cur += delta;		/* form error * 7 */+
−
	/* At this point cur contains the 7/16 error value to be propagated+
−
	 * to the next pixel on the current line, and all the errors for the+
−
	 * next line have been shifted over. We are therefore ready to move on.+
−
	 */+
−
	input_ptr += dirnc;	/* advance input ptr to next column */+
−
	output_ptr += dir;	/* advance output ptr to next column */+
−
	errorptr += dir;	/* advance errorptr to current column */+
−
      }+
−
      /* Post-loop cleanup: we must unload the final error value into the+
−
       * final fserrors[] entry.  Note we need not unload belowerr because+
−
       * it is for the dummy column before or after the actual array.+
−
       */+
−
      errorptr[0] = (FSERROR) bpreverr; /* unload prev err into array */+
−
    }+
−
    cquantize->on_odd_row = (cquantize->on_odd_row ? FALSE : TRUE);+
−
  }+
−
}+
−
+
−
+
−
/*+
−
 * Allocate workspace for Floyd-Steinberg errors.+
−
 */+
−
+
−
LOCAL(void)+
−
alloc_fs_workspace (j_decompress_ptr cinfo)+
−
{+
−
  my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;+
−
  size_t arraysize;+
−
  int i;+
−
+
−
  arraysize = (size_t) ((cinfo->output_width + 2) * SIZEOF(FSERROR));+
−
  for (i = 0; i < cinfo->out_color_components; i++) {+
−
    cquantize->fserrors[i] = (FSERRPTR)+
−
      (*cinfo->mem->alloc_large)((j_common_ptr) cinfo, JPOOL_IMAGE, arraysize);+
−
  }+
−
}+
−
+
−
+
−
/*+
−
 * Initialize for one-pass color quantization.+
−
 */+
−
+
−
METHODDEF(void)+
−
start_pass_1_quant (j_decompress_ptr cinfo, boolean is_pre_scan)+
−
{+
−
  my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;+
−
  size_t arraysize;+
−
  int i;+
−
+
−
  /* Install my colormap. */+
−
  cinfo->colormap = cquantize->sv_colormap;+
−
  cinfo->actual_number_of_colors = cquantize->sv_actual;+
−
+
−
  /* Initialize for desired dithering mode. */+
−
  switch (cinfo->dither_mode) {+
−
  case JDITHER_NONE:+
−
    if (cinfo->out_color_components == 3)+
−
      cquantize->pub.color_quantize = color_quantize3;+
−
    else+
−
      cquantize->pub.color_quantize = color_quantize;+
−
    break;+
−
  case JDITHER_ORDERED:+
−
    if (cinfo->out_color_components == 3)+
−
      cquantize->pub.color_quantize = quantize3_ord_dither;+
−
    else+
−
      cquantize->pub.color_quantize = quantize_ord_dither;+
−
    cquantize->row_index = 0;	/* initialize state for ordered dither */+
−
    /* If user changed to ordered dither from another mode,+
−
     * we must recreate the color index table with padding.+
−
     * This will cost extra space, but probably isn't very likely.+
−
     */+
−
    if (! cquantize->is_padded)+
−
      create_colorindex(cinfo);+
−
    /* Create ordered-dither tables if we didn't already. */+
−
    if (cquantize->odither[0] == NULL)+
−
      create_odither_tables(cinfo);+
−
    break;+
−
  case JDITHER_FS:+
−
    cquantize->pub.color_quantize = quantize_fs_dither;+
−
    cquantize->on_odd_row = FALSE; /* initialize state for F-S dither */+
−
    /* Allocate Floyd-Steinberg workspace if didn't already. */+
−
    if (cquantize->fserrors[0] == NULL)+
−
      alloc_fs_workspace(cinfo);+
−
    /* Initialize the propagated errors to zero. */+
−
    arraysize = (size_t) ((cinfo->output_width + 2) * SIZEOF(FSERROR));+
−
    for (i = 0; i < cinfo->out_color_components; i++)+
−
      jzero_far((void FAR *) cquantize->fserrors[i], arraysize);+
−
    break;+
−
  default:+
−
    ERREXIT(cinfo, JERR_NOT_COMPILED);+
−
    break;+
−
  }+
−
}+
−
+
−
+
−
/*+
−
 * Finish up at the end of the pass.+
−
 */+
−
+
−
METHODDEF(void)+
−
finish_pass_1_quant (j_decompress_ptr cinfo)+
−
{+
−
  /* no work in 1-pass case */+
−
}+
−
+
−
+
−
/*+
−
 * Switch to a new external colormap between output passes.+
−
 * Shouldn't get to this module!+
−
 */+
−
+
−
METHODDEF(void)+
−
new_color_map_1_quant (j_decompress_ptr cinfo)+
−
{+
−
  ERREXIT(cinfo, JERR_MODE_CHANGE);+
−
}+
−
+
−
+
−
/*+
−
 * Module initialization routine for 1-pass color quantization.+
−
 */+
−
+
−
GLOBAL(void)+
−
jinit_1pass_quantizer (j_decompress_ptr cinfo)+
−
{+
−
  my_cquantize_ptr cquantize;+
−
+
−
  cquantize = (my_cquantize_ptr)+
−
    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,+
−
				SIZEOF(my_cquantizer));+
−
  cinfo->cquantize = (struct jpeg_color_quantizer *) cquantize;+
−
  cquantize->pub.start_pass = start_pass_1_quant;+
−
  cquantize->pub.finish_pass = finish_pass_1_quant;+
−
  cquantize->pub.new_color_map = new_color_map_1_quant;+
−
  cquantize->fserrors[0] = NULL; /* Flag FS workspace not allocated */+
−
  cquantize->odither[0] = NULL;	/* Also flag odither arrays not allocated */+
−
+
−
  /* Make sure my internal arrays won't overflow */+
−
  if (cinfo->out_color_components > MAX_Q_COMPS)+
−
    ERREXIT1(cinfo, JERR_QUANT_COMPONENTS, MAX_Q_COMPS);+
−
  /* Make sure colormap indexes can be represented by JSAMPLEs */+
−
  if (cinfo->desired_number_of_colors > (MAXJSAMPLE+1))+
−
    ERREXIT1(cinfo, JERR_QUANT_MANY_COLORS, MAXJSAMPLE+1);+
−
+
−
  /* Create the colormap and color index table. */+
−
  create_colormap(cinfo);+
−
  create_colorindex(cinfo);+
−
+
−
  /* Allocate Floyd-Steinberg workspace now if requested.+
−
   * We do this now since it is FAR storage and may affect the memory+
−
   * manager's space calculations.  If the user changes to FS dither+
−
   * mode in a later pass, we will allocate the space then, and will+
−
   * possibly overrun the max_memory_to_use setting.+
−
   */+
−
  if (cinfo->dither_mode == JDITHER_FS)+
−
    alloc_fs_workspace(cinfo);+
−
}+
−
+
−
#endif /* QUANT_1PASS_SUPPORTED */+
−