/*

* jquant1.c

*

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

* Modified 2011 by Guido Vollbeding.

* 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 1-pass color quantization (color mapping) routines.

* These routines provide mapping to a fixed color map using equally spaced

* color values. Optional Floyd-Steinberg or ordered dithering is available.

*/

#define JPEG_INTERNALS

#include "jinclude.h"

#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.

*/

/* Declarations for ordered dithering.

*

* We use a standard 16x16 ordered dither array. The basic concept of ordered

* 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.

*/

#define ODITHER_SIZE 16 /* dimension of dither matrix */

/* NB: if ODITHER_SIZE is not a power of 2, ODITHER_MASK uses will break */

#define ODITHER_CELLS (ODITHER_SIZE*ODITHER_SIZE) /* # cells in matrix */

#define ODITHER_MASK (ODITHER_SIZE-1) /* mask for wrapping around counters */

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] = {

/* Bayer's order-4 dither array. Generated by the code given in

* Stephen Hawley's article "Ordered Dithering" in Graphics Gems I.

* The values in this array must range from 0 to ODITHER_CELLS-1.

*/

{ 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 }

};

/* Declarations for Floyd-Steinberg dithering.

*

* Errors are accumulated into the array fserrors[], at a resolution of

* 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

* 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].

* We provide (#columns + 2) entries per component; the extra entry at each

* end saves us from special-casing the first and last pixels.

*

* 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

typedef INT16 FSERROR; /* 16 bits should be enough */

typedef int LOCFSERROR; /* use 'int' for calculation temps */

#else

typedef INT32 FSERROR; /* may need more than 16 bits */

typedef INT32 LOCFSERROR; /* be sure calculation temps are big enough */

#endif

typedef FSERROR FAR *FSERRPTR; /* pointer to error array (in FAR storage!) */

/* Private subobject */

#define MAX_Q_COMPS 4 /* max components I can handle */

typedef struct {

struct jpeg_color_quantizer pub; /* public fields */

/* Initially allocated colormap is saved here */

JSAMPARRAY sv_colormap; /* The color map as a 2-D pixel array */

int sv_actual; /* number of entries in use */

JSAMPARRAY colorindex; /* Precomputed mapping for speed */

/* colorindex[i][j] = index of color closest to pixel value j in component i,

* premultiplied as described above. Since colormap indexes must fit into

* JSAMPLEs, the entries of this array will too.

*/

boolean is_padded; /* is the colorindex padded for odither? */

int Ncolors[MAX_Q_COMPS]; /* # of values alloced to each component */

/* Variables for ordered dithering */

int row_index; /* cur row's vertical index in dither matrix */

ODITHER_MATRIX_PTR odither[MAX_Q_COMPS]; /* one dither array per component */

/* Variables for Floyd-Steinberg dithering */

FSERRPTR fserrors[MAX_Q_COMPS]; /* accumulated errors */

boolean on_odd_row; /* flag to remember which row we are on */

} my_cquantizer;

typedef my_cquantizer * my_cquantize_ptr;

/*

* 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.

*

* * select_ncolors decides how to divvy up the available colors

* among the components.

* * output_value defines the set of representative values for a component.

* * 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

* different components, though this is not currently done.

*/

LOCAL(int)

select_ncolors (j_decompress_ptr cinfo, int Ncolors[])

/* Determine allocation of desired colors to components, */

/* and fill in Ncolors[] array to indicate choice. */

/* Return value is total number of colors (product of Ncolors[] values). */

{

int nc = cinfo->out_color_components; /* number of color components */

int max_colors = cinfo->desired_number_of_colors;

int total_colors, iroot, i, j;

boolean changed;

long temp;

static const int RGB_order[3] = { RGB_GREEN, RGB_RED, RGB_BLUE };

/* 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++;

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;

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

* exceeding max_colors, though we know not all can be incremented.

* 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.

* (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,

(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 */

FMEMZERO((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 */

FMEMZERO((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++)

FMEMZERO((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 */