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libimagequant is derived from code by Jef Poskanzer and Greg Roelofs
licensed under pngquant's original license (at the end of this file),
and contains extensive changes and additions by Kornel Lesiński
licensed under GPL v3.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
libimagequant © 2009-2016 by Kornel Lesiński.
GNU GENERAL PUBLIC LICENSE
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- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
© 1989, 1991 by Jef Poskanzer.
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/*
© 2011-2015 by Kornel Lesiński.
This file is part of libimagequant.
libimagequant is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
libimagequant is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with libimagequant. If not, see <http://www.gnu.org/licenses/>.
*/
#include "libimagequant.h"
#include "pam.h"
#include "blur.h"
/*
Blurs image horizontally (width 2*size+1) and writes it transposed to dst (called twice gives 2d blur)
*/
static void transposing_1d_blur(unsigned char *restrict src, unsigned char *restrict dst, unsigned int width, unsigned int height, const unsigned int size)
{
assert(size > 0);
for(unsigned int j=0; j < height; j++) {
unsigned char *restrict row = src + j*width;
// accumulate sum for pixels outside line
unsigned int sum;
sum = row[0]*size;
for(unsigned int i=0; i < size; i++) {
sum += row[i];
}
// blur with left side outside line
for(unsigned int i=0; i < size; i++) {
sum -= row[0];
sum += row[i+size];
dst[i*height + j] = sum / (size*2);
}
for(unsigned int i=size; i < width-size; i++) {
sum -= row[i-size];
sum += row[i+size];
dst[i*height + j] = sum / (size*2);
}
// blur with right side outside line
for(unsigned int i=width-size; i < width; i++) {
sum -= row[i-size];
sum += row[width-1];
dst[i*height + j] = sum / (size*2);
}
}
}
/**
* Picks maximum of neighboring pixels (blur + lighten)
*/
LIQ_PRIVATE void liq_max3(unsigned char *src, unsigned char *dst, unsigned int width, unsigned int height)
{
for(unsigned int j=0; j < height; j++) {
const unsigned char *row = src + j*width,
*prevrow = src + (j > 1 ? j-1 : 0)*width,
*nextrow = src + MIN(height-1,j+1)*width;
unsigned char prev,curr=row[0],next=row[0];
for(unsigned int i=0; i < width-1; i++) {
prev=curr;
curr=next;
next=row[i+1];
unsigned char t1 = MAX(prev,next);
unsigned char t2 = MAX(nextrow[i],prevrow[i]);
*dst++ = MAX(curr,MAX(t1,t2));
}
unsigned char t1 = MAX(curr,next);
unsigned char t2 = MAX(nextrow[width-1],prevrow[width-1]);
*dst++ = MAX(t1,t2);
}
}
/**
* Picks minimum of neighboring pixels (blur + darken)
*/
LIQ_PRIVATE void liq_min3(unsigned char *src, unsigned char *dst, unsigned int width, unsigned int height)
{
for(unsigned int j=0; j < height; j++) {
const unsigned char *row = src + j*width,
*prevrow = src + (j > 1 ? j-1 : 0)*width,
*nextrow = src + MIN(height-1,j+1)*width;
unsigned char prev,curr=row[0],next=row[0];
for(unsigned int i=0; i < width-1; i++) {
prev=curr;
curr=next;
next=row[i+1];
unsigned char t1 = MIN(prev,next);
unsigned char t2 = MIN(nextrow[i],prevrow[i]);
*dst++ = MIN(curr,MIN(t1,t2));
}
unsigned char t1 = MIN(curr,next);
unsigned char t2 = MIN(nextrow[width-1],prevrow[width-1]);
*dst++ = MIN(t1,t2);
}
}
/*
Filters src image and saves it to dst, overwriting tmp in the process.
Image must be width*height pixels high. Size controls radius of box blur.
*/
LIQ_PRIVATE void liq_blur(unsigned char *src, unsigned char *tmp, unsigned char *dst, unsigned int width, unsigned int height, unsigned int size)
{
assert(size > 0);
if (width < 2*size+1 || height < 2*size+1) {
return;
}
transposing_1d_blur(src, tmp, width, height, size);
transposing_1d_blur(tmp, dst, height, width, size);
}

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LIQ_PRIVATE void liq_blur(unsigned char *src, unsigned char *tmp, unsigned char *dst, unsigned int width, unsigned int height, unsigned int size);
LIQ_PRIVATE void liq_max3(unsigned char *src, unsigned char *dst, unsigned int width, unsigned int height);
LIQ_PRIVATE void liq_min3(unsigned char *src, unsigned char *dst, unsigned int width, unsigned int height);

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/*
* https://pngquant.org
*/
#ifndef LIBIMAGEQUANT_H
#define LIBIMAGEQUANT_H
#ifdef IMAGEQUANT_EXPORTS
#define LIQ_EXPORT __declspec(dllexport)
#endif
#ifndef LIQ_EXPORT
#define LIQ_EXPORT extern
#endif
#define LIQ_VERSION 20800
#define LIQ_VERSION_STRING "2.8.0"
#ifndef LIQ_PRIVATE
#if defined(__GNUC__) || defined (__llvm__)
#define LIQ_PRIVATE __attribute__((visibility("hidden")))
#define LIQ_NONNULL __attribute__((nonnull))
#define LIQ_USERESULT __attribute__((warn_unused_result))
#else
#define LIQ_PRIVATE
#define LIQ_NONNULL
#define LIQ_USERESULT
#endif
#endif
#ifdef __cplusplus
extern "C" {
#endif
#include <stddef.h>
typedef struct liq_attr liq_attr;
typedef struct liq_image liq_image;
typedef struct liq_result liq_result;
typedef struct liq_histogram liq_histogram;
typedef struct liq_color {
unsigned char r, g, b, a;
} liq_color;
typedef struct liq_palette {
unsigned int count;
liq_color entries[256];
} liq_palette;
typedef enum liq_error {
LIQ_OK = 0,
LIQ_QUALITY_TOO_LOW = 99,
LIQ_VALUE_OUT_OF_RANGE = 100,
LIQ_OUT_OF_MEMORY,
LIQ_ABORTED,
LIQ_BITMAP_NOT_AVAILABLE,
LIQ_BUFFER_TOO_SMALL,
LIQ_INVALID_POINTER,
} liq_error;
enum liq_ownership {LIQ_OWN_ROWS=4, LIQ_OWN_PIXELS=8};
LIQ_EXPORT LIQ_USERESULT liq_attr* liq_attr_create(void);
LIQ_EXPORT LIQ_USERESULT liq_attr* liq_attr_create_with_allocator(void* (*malloc)(size_t), void (*free)(void*));
LIQ_EXPORT LIQ_USERESULT liq_attr* liq_attr_copy(liq_attr *orig) LIQ_NONNULL;
LIQ_EXPORT void liq_attr_destroy(liq_attr *attr) LIQ_NONNULL;
LIQ_EXPORT LIQ_USERESULT liq_histogram* liq_histogram_create(liq_attr* attr);
LIQ_EXPORT LIQ_USERESULT liq_error liq_histogram_add_image(liq_histogram *hist, liq_attr *attr, liq_image* image);
LIQ_EXPORT void liq_histogram_destroy(liq_histogram *hist) LIQ_NONNULL;
LIQ_EXPORT liq_error liq_set_max_colors(liq_attr* attr, int colors) LIQ_NONNULL;
LIQ_EXPORT LIQ_USERESULT int liq_get_max_colors(const liq_attr* attr) LIQ_NONNULL;
LIQ_EXPORT liq_error liq_set_speed(liq_attr* attr, int speed) LIQ_NONNULL;
LIQ_EXPORT LIQ_USERESULT int liq_get_speed(const liq_attr* attr) LIQ_NONNULL;
LIQ_EXPORT liq_error liq_set_min_opacity(liq_attr* attr, int min) LIQ_NONNULL;
LIQ_EXPORT LIQ_USERESULT int liq_get_min_opacity(const liq_attr* attr) LIQ_NONNULL;
LIQ_EXPORT liq_error liq_set_min_posterization(liq_attr* attr, int bits) LIQ_NONNULL;
LIQ_EXPORT LIQ_USERESULT int liq_get_min_posterization(const liq_attr* attr) LIQ_NONNULL;
LIQ_EXPORT liq_error liq_set_quality(liq_attr* attr, int minimum, int maximum) LIQ_NONNULL;
LIQ_EXPORT LIQ_USERESULT int liq_get_min_quality(const liq_attr* attr) LIQ_NONNULL;
LIQ_EXPORT LIQ_USERESULT int liq_get_max_quality(const liq_attr* attr) LIQ_NONNULL;
LIQ_EXPORT void liq_set_last_index_transparent(liq_attr* attr, int is_last) LIQ_NONNULL;
typedef void liq_log_callback_function(const liq_attr*, const char *message, void* user_info);
typedef void liq_log_flush_callback_function(const liq_attr*, void* user_info);
LIQ_EXPORT void liq_set_log_callback(liq_attr*, liq_log_callback_function*, void* user_info);
LIQ_EXPORT void liq_set_log_flush_callback(liq_attr*, liq_log_flush_callback_function*, void* user_info);
typedef int liq_progress_callback_function(float progress_percent, void* user_info);
LIQ_EXPORT void liq_attr_set_progress_callback(liq_attr*, liq_progress_callback_function*, void* user_info);
LIQ_EXPORT void liq_result_set_progress_callback(liq_result*, liq_progress_callback_function*, void* user_info);
// The rows and their data are not modified. The type of `rows` is non-const only due to a bug in C's typesystem design.
LIQ_EXPORT LIQ_USERESULT liq_image *liq_image_create_rgba_rows(const liq_attr *attr, void *const rows[], int width, int height, double gamma) LIQ_NONNULL;
LIQ_EXPORT LIQ_USERESULT liq_image *liq_image_create_rgba(const liq_attr *attr, const void *bitmap, int width, int height, double gamma) LIQ_NONNULL;
typedef void liq_image_get_rgba_row_callback(liq_color row_out[], int row, int width, void* user_info);
LIQ_EXPORT LIQ_USERESULT liq_image *liq_image_create_custom(const liq_attr *attr, liq_image_get_rgba_row_callback *row_callback, void* user_info, int width, int height, double gamma);
LIQ_EXPORT liq_error liq_image_set_memory_ownership(liq_image *image, int ownership_flags) LIQ_NONNULL;
LIQ_EXPORT liq_error liq_image_add_fixed_color(liq_image *img, liq_color color) LIQ_NONNULL;
LIQ_EXPORT LIQ_USERESULT int liq_image_get_width(const liq_image *img) LIQ_NONNULL;
LIQ_EXPORT LIQ_USERESULT int liq_image_get_height(const liq_image *img) LIQ_NONNULL;
LIQ_EXPORT void liq_image_destroy(liq_image *img) LIQ_NONNULL;
LIQ_EXPORT LIQ_USERESULT liq_error liq_histogram_quantize(liq_histogram *const input_hist, liq_attr *const options, liq_result **result_output) LIQ_NONNULL;
LIQ_EXPORT LIQ_USERESULT liq_error liq_image_quantize(liq_image *const input_image, liq_attr *const options, liq_result **result_output) LIQ_NONNULL;
LIQ_EXPORT liq_error liq_set_dithering_level(liq_result *res, float dither_level) LIQ_NONNULL;
LIQ_EXPORT liq_error liq_set_output_gamma(liq_result* res, double gamma) LIQ_NONNULL;
LIQ_EXPORT LIQ_USERESULT double liq_get_output_gamma(const liq_result *result) LIQ_NONNULL;
LIQ_EXPORT LIQ_USERESULT const liq_palette *liq_get_palette(liq_result *result) LIQ_NONNULL;
LIQ_EXPORT liq_error liq_write_remapped_image(liq_result *result, liq_image *input_image, void *buffer, size_t buffer_size) LIQ_NONNULL;
LIQ_EXPORT liq_error liq_write_remapped_image_rows(liq_result *result, liq_image *input_image, unsigned char **row_pointers) LIQ_NONNULL;
LIQ_EXPORT double liq_get_quantization_error(liq_result *result) LIQ_NONNULL;
LIQ_EXPORT int liq_get_quantization_quality(liq_result *result) LIQ_NONNULL;
LIQ_EXPORT double liq_get_remapping_error(liq_result *result) LIQ_NONNULL;
LIQ_EXPORT int liq_get_remapping_quality(liq_result *result) LIQ_NONNULL;
LIQ_EXPORT void liq_result_destroy(liq_result *) LIQ_NONNULL;
LIQ_EXPORT int liq_version(void);
// Deprecated
LIQ_EXPORT LIQ_USERESULT liq_result *liq_quantize_image(liq_attr *options, liq_image *input_image) LIQ_NONNULL;
#ifdef __cplusplus
}
#endif
#endif

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/*
** © 2009-2015 by Kornel Lesiński.
**
** This file is part of libimagequant.
**
** libimagequant is free software: you can redistribute it and/or modify
** it under the terms of the GNU General Public License as published by
** the Free Software Foundation, either version 3 of the License, or
** (at your option) any later version.
**
** libimagequant is distributed in the hope that it will be useful,
** but WITHOUT ANY WARRANTY; without even the implied warranty of
** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
** GNU General Public License for more details.
**
** You should have received a copy of the GNU General Public License
** along with libimagequant. If not, see <http://www.gnu.org/licenses/>.
*/
/*
** Copyright (C) 1989, 1991 by Jef Poskanzer.
** Copyright (C) 1997, 2000, 2002 by Greg Roelofs; based on an idea by
** Stefan Schneider.
**
** Permission to use, copy, modify, and distribute this software and its
** documentation for any purpose and without fee is hereby granted, provided
** that the above copyright notice appear in all copies and that both that
** copyright notice and this permission notice appear in supporting
** documentation. This software is provided "as is" without express or
** implied warranty.
*/
#include <stdlib.h>
#include <stddef.h>
#include "libimagequant.h"
#include "pam.h"
#include "mediancut.h"
#define index_of_channel(ch) (offsetof(f_pixel,ch)/sizeof(float))
static f_pixel averagepixels(unsigned int clrs, const hist_item achv[], const f_pixel center);
struct box {
f_pixel color;
f_pixel variance;
double sum, total_error, max_error;
unsigned int ind;
unsigned int colors;
};
ALWAYS_INLINE static double variance_diff(double val, const double good_enough);
inline static double variance_diff(double val, const double good_enough)
{
val *= val;
if (val < good_enough*good_enough) return val*0.25;
return val;
}
/** Weighted per-channel variance of the box. It's used to decide which channel to split by */
static f_pixel box_variance(const hist_item achv[], const struct box *box)
{
f_pixel mean = box->color;
double variancea=0, variancer=0, varianceg=0, varianceb=0;
for(unsigned int i = 0; i < box->colors; ++i) {
f_pixel px = achv[box->ind + i].acolor;
double weight = achv[box->ind + i].adjusted_weight;
variancea += variance_diff(mean.a - px.a, 2.0/256.0)*weight;
variancer += variance_diff(mean.r - px.r, 1.0/256.0)*weight;
varianceg += variance_diff(mean.g - px.g, 1.0/256.0)*weight;
varianceb += variance_diff(mean.b - px.b, 1.0/256.0)*weight;
}
return (f_pixel){
.a = variancea*(4.0/16.0),
.r = variancer*(7.0/16.0),
.g = varianceg*(9.0/16.0),
.b = varianceb*(5.0/16.0),
};
}
static double box_max_error(const hist_item achv[], const struct box *box)
{
f_pixel mean = box->color;
double max_error = 0;
for(unsigned int i = 0; i < box->colors; ++i) {
const double diff = colordifference(mean, achv[box->ind + i].acolor);
if (diff > max_error) {
max_error = diff;
}
}
return max_error;
}
ALWAYS_INLINE static double color_weight(f_pixel median, hist_item h);
static inline void hist_item_swap(hist_item *l, hist_item *r)
{
if (l != r) {
hist_item t = *l;
*l = *r;
*r = t;
}
}
ALWAYS_INLINE static unsigned int qsort_pivot(const hist_item *const base, const unsigned int len);
inline static unsigned int qsort_pivot(const hist_item *const base, const unsigned int len)
{
if (len < 32) {
return len/2;
}
const unsigned int aidx=8, bidx=len/2, cidx=len-1;
const unsigned int a=base[aidx].tmp.sort_value, b=base[bidx].tmp.sort_value, c=base[cidx].tmp.sort_value;
return (a < b) ? ((b < c) ? bidx : ((a < c) ? cidx : aidx ))
: ((b > c) ? bidx : ((a < c) ? aidx : cidx ));
}
ALWAYS_INLINE static unsigned int qsort_partition(hist_item *const base, const unsigned int len);
inline static unsigned int qsort_partition(hist_item *const base, const unsigned int len)
{
unsigned int l = 1, r = len;
if (len >= 8) {
hist_item_swap(&base[0], &base[qsort_pivot(base,len)]);
}
const unsigned int pivot_value = base[0].tmp.sort_value;
while (l < r) {
if (base[l].tmp.sort_value >= pivot_value) {
l++;
} else {
while(l < --r && base[r].tmp.sort_value <= pivot_value) {}
hist_item_swap(&base[l], &base[r]);
}
}
l--;
hist_item_swap(&base[0], &base[l]);
return l;
}
/** quick select algorithm */
static void hist_item_sort_range(hist_item *base, unsigned int len, unsigned int sort_start)
{
for(;;) {
const unsigned int l = qsort_partition(base, len), r = l+1;
if (l > 0 && sort_start < l) {
len = l;
}
else if (r < len && sort_start > r) {
base += r; len -= r; sort_start -= r;
}
else break;
}
}
/** sorts array to make sum of weights lower than halfvar one side, returns edge between <halfvar and >halfvar parts of the set */
static hist_item *hist_item_sort_halfvar(hist_item *base, unsigned int len, double *const lowervar, const double halfvar)
{
do {
const unsigned int l = qsort_partition(base, len), r = l+1;
// check if sum of left side is smaller than half,
// if it is, then it doesn't need to be sorted
unsigned int t = 0; double tmpsum = *lowervar;
while (t <= l && tmpsum < halfvar) tmpsum += base[t++].color_weight;
if (tmpsum < halfvar) {
*lowervar = tmpsum;
} else {
if (l > 0) {
hist_item *res = hist_item_sort_halfvar(base, l, lowervar, halfvar);
if (res) return res;
} else {
// End of left recursion. This will be executed in order from the first element.
*lowervar += base[0].color_weight;
if (*lowervar > halfvar) return &base[0];
}
}
if (len > r) {
base += r; len -= r; // tail-recursive "call"
} else {
*lowervar += base[r].color_weight;
return (*lowervar > halfvar) ? &base[r] : NULL;
}
} while(1);
}
static f_pixel get_median(const struct box *b, hist_item achv[]);
typedef struct {
unsigned int chan; float variance;
} channelvariance;
static int comparevariance(const void *ch1, const void *ch2)
{
return ((const channelvariance*)ch1)->variance > ((const channelvariance*)ch2)->variance ? -1 :
(((const channelvariance*)ch1)->variance < ((const channelvariance*)ch2)->variance ? 1 : 0);
}
/** Finds which channels need to be sorted first and preproceses achv for fast sort */
static double prepare_sort(struct box *b, hist_item achv[])
{
/*
** Sort dimensions by their variance, and then sort colors first by dimension with highest variance
*/
channelvariance channels[4] = {
{index_of_channel(r), b->variance.r},
{index_of_channel(g), b->variance.g},
{index_of_channel(b), b->variance.b},
{index_of_channel(a), b->variance.a},
};
qsort(channels, 4, sizeof(channels[0]), comparevariance);
for(unsigned int i=0; i < b->colors; i++) {
const float *chans = (const float *)&achv[b->ind + i].acolor;
// Only the first channel really matters. When trying median cut many times
// with different histogram weights, I don't want sort randomness to influence outcome.
achv[b->ind + i].tmp.sort_value = ((unsigned int)(chans[channels[0].chan]*65535.0)<<16) |
(unsigned int)((chans[channels[2].chan] + chans[channels[1].chan]/2.0 + chans[channels[3].chan]/4.0)*65535.0);
}
const f_pixel median = get_median(b, achv);
// box will be split to make color_weight of each side even
const unsigned int ind = b->ind, end = ind+b->colors;
double totalvar = 0;
for(unsigned int j=ind; j < end; j++) totalvar += (achv[j].color_weight = color_weight(median, achv[j]));
return totalvar / 2.0;
}
/** finds median in unsorted set by sorting only minimum required */
static f_pixel get_median(const struct box *b, hist_item achv[])
{
const unsigned int median_start = (b->colors-1)/2;
hist_item_sort_range(&(achv[b->ind]), b->colors,
median_start);
if (b->colors&1) return achv[b->ind + median_start].acolor;
// technically the second color is not guaranteed to be sorted correctly
// but most of the time it is good enough to be useful
return averagepixels(2, &achv[b->ind + median_start], (f_pixel){0.5,0.5,0.5,0.5});
}
/*
** Find the best splittable box. -1 if no boxes are splittable.
*/
static int best_splittable_box(struct box* bv, unsigned int boxes, const double max_mse)
{
int bi=-1; double maxsum=0;
for(unsigned int i=0; i < boxes; i++) {
if (bv[i].colors < 2) {
continue;
}
// looks only at max variance, because it's only going to split by it
const double cv = MAX(bv[i].variance.r, MAX(bv[i].variance.g,bv[i].variance.b));
double thissum = bv[i].sum * MAX(bv[i].variance.a, cv);
if (bv[i].max_error > max_mse) {
thissum = thissum* bv[i].max_error/max_mse;
}
if (thissum > maxsum) {
maxsum = thissum;
bi = i;
}
}
return bi;
}
inline static double color_weight(f_pixel median, hist_item h)
{
float diff = colordifference(median, h.acolor);
// if color is "good enough", don't split further
if (diff < 1.f/256.f/256.f) diff /= 2.f;
return sqrt(diff) * (sqrt(1.0+h.adjusted_weight)-1.0);
}
static void set_colormap_from_boxes(colormap *map, struct box* bv, unsigned int boxes, hist_item *achv);
static void adjust_histogram(hist_item *achv, const colormap *map, const struct box* bv, unsigned int boxes);
static double box_error(const struct box *box, const hist_item achv[])
{
f_pixel avg = box->color;
double total_error=0;
for (unsigned int i = 0; i < box->colors; ++i) {
total_error += colordifference(avg, achv[box->ind + i].acolor) * achv[box->ind + i].perceptual_weight;
}
return total_error;
}
static bool total_box_error_below_target(double target_mse, struct box bv[], unsigned int boxes, const histogram *hist)
{
target_mse *= hist->total_perceptual_weight;
double total_error=0;
for(unsigned int i=0; i < boxes; i++) {
// error is (re)calculated lazily
if (bv[i].total_error >= 0) {
total_error += bv[i].total_error;
}
if (total_error > target_mse) return false;
}
for(unsigned int i=0; i < boxes; i++) {
if (bv[i].total_error < 0) {
bv[i].total_error = box_error(&bv[i], hist->achv);
total_error += bv[i].total_error;
}
if (total_error > target_mse) return false;
}
return true;
}
/*
** Here is the fun part, the median-cut colormap generator. This is based
** on Paul Heckbert's paper, "Color Image Quantization for Frame Buffer
** Display," SIGGRAPH 1982 Proceedings, page 297.
*/
LIQ_PRIVATE colormap *mediancut(histogram *hist, unsigned int newcolors, const double target_mse, const double max_mse, void* (*malloc)(size_t), void (*free)(void*))
{
hist_item *achv = hist->achv;
struct box bv[newcolors];
/*
** Set up the initial box.
*/
bv[0].ind = 0;
bv[0].colors = hist->size;
bv[0].color = averagepixels(bv[0].colors, &achv[bv[0].ind], (f_pixel){0.5,0.5,0.5,0.5});
bv[0].variance = box_variance(achv, &bv[0]);
bv[0].max_error = box_max_error(achv, &bv[0]);
bv[0].sum = 0;
bv[0].total_error = -1;
for(unsigned int i=0; i < bv[0].colors; i++) bv[0].sum += achv[i].adjusted_weight;
unsigned int boxes = 1;
/*
** Main loop: split boxes until we have enough.
*/
while (boxes < newcolors) {
// first splits boxes that exceed quality limit (to have colors for things like odd green pixel),
// later raises the limit to allow large smooth areas/gradients get colors.
const double current_max_mse = max_mse + (boxes/(double)newcolors)*16.0*max_mse;
const int bi = best_splittable_box(bv, boxes, current_max_mse);
if (bi < 0)
break; /* ran out of colors! */
unsigned int indx = bv[bi].ind;
unsigned int clrs = bv[bi].colors;
/*
Classic implementation tries to get even number of colors or pixels in each subdivision.
Here, instead of popularity I use (sqrt(popularity)*variance) metric.
Each subdivision balances number of pixels (popular colors) and low variance -
boxes can be large if they have similar colors. Later boxes with high variance
will be more likely to be split.
Median used as expected value gives much better results than mean.
*/
const double halfvar = prepare_sort(&bv[bi], achv);
double lowervar=0;
// hist_item_sort_halfvar sorts and sums lowervar at the same time
// returns item to break at …minus one, which does smell like an off-by-one error.
hist_item *break_p = hist_item_sort_halfvar(&achv[indx], clrs, &lowervar, halfvar);
unsigned int break_at = MIN(clrs-1, break_p - &achv[indx] + 1);
/*
** Split the box.
*/
double sm = bv[bi].sum;
double lowersum = 0;
for(unsigned int i=0; i < break_at; i++) lowersum += achv[indx + i].adjusted_weight;
const f_pixel previous_center = bv[bi].color;
bv[bi].colors = break_at;
bv[bi].sum = lowersum;
bv[bi].color = averagepixels(bv[bi].colors, &achv[bv[bi].ind], previous_center);
bv[bi].total_error = -1;
bv[bi].variance = box_variance(achv, &bv[bi]);
bv[bi].max_error = box_max_error(achv, &bv[bi]);
bv[boxes].ind = indx + break_at;
bv[boxes].colors = clrs - break_at;
bv[boxes].sum = sm - lowersum;
bv[boxes].color = averagepixels(bv[boxes].colors, &achv[bv[boxes].ind], previous_center);
bv[boxes].total_error = -1;
bv[boxes].variance = box_variance(achv, &bv[boxes]);
bv[boxes].max_error = box_max_error(achv, &bv[boxes]);
++boxes;
if (total_box_error_below_target(target_mse, bv, boxes, hist)) {
break;
}
}
colormap *map = pam_colormap(boxes, malloc, free);
set_colormap_from_boxes(map, bv, boxes, achv);
adjust_histogram(achv, map, bv, boxes);
return map;
}
static void set_colormap_from_boxes(colormap *map, struct box* bv, unsigned int boxes, hist_item *achv)
{
/*
** Ok, we've got enough boxes. Now choose a representative color for
** each box. There are a number of possible ways to make this choice.
** One would be to choose the center of the box; this ignores any structure
** within the boxes. Another method would be to average all the colors in
** the box - this is the method specified in Heckbert's paper.
*/
for(unsigned int bi = 0; bi < boxes; ++bi) {
map->palette[bi].acolor = bv[bi].color;
/* store total color popularity (perceptual_weight is approximation of it) */
map->palette[bi].popularity = 0;
for(unsigned int i=bv[bi].ind; i < bv[bi].ind+bv[bi].colors; i++) {
map->palette[bi].popularity += achv[i].perceptual_weight;
}
}
}
/* increase histogram popularity by difference from the final color (this is used as part of feedback loop) */
static void adjust_histogram(hist_item *achv, const colormap *map, const struct box* bv, unsigned int boxes)
{
for(unsigned int bi = 0; bi < boxes; ++bi) {
for(unsigned int i=bv[bi].ind; i < bv[bi].ind+bv[bi].colors; i++) {
achv[i].adjusted_weight *= sqrt(1.0 +colordifference(map->palette[bi].acolor, achv[i].acolor)/2.0);
achv[i].tmp.likely_colormap_index = bi;
}
}
}
static f_pixel averagepixels(unsigned int clrs, const hist_item achv[], f_pixel center)
{
double r = 0, g = 0, b = 0, a = 0, sum = 0;
for(unsigned int i = 0; i < clrs; i++) {
const f_pixel px = achv[i].acolor;
const double weight = achv[i].adjusted_weight;
sum += weight;
r += px.r * weight;
g += px.g * weight;
b += px.b * weight;
a += px.a * weight;
}
if (sum) {
a /= sum;
r /= sum;
g /= sum;
b /= sum;
}
assert(!isnan(r) && !isnan(g) && !isnan(b) && !isnan(a));
return (f_pixel){.r=r, .g=g, .b=b, .a=a};
}

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LIQ_PRIVATE colormap *mediancut(histogram *hist, unsigned int newcolors, const double target_mse, const double max_mse, void* (*malloc)(size_t), void (*free)(void*));

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/*
© 2011-2016 by Kornel Lesiński.
This file is part of libimagequant.
libimagequant is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
libimagequant is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with libimagequant. If not, see <http://www.gnu.org/licenses/>.
*/
#include "libimagequant.h"
#include "mempool.h"
#include <stdlib.h>
#include <stdint.h>
#include <assert.h>
#define ALIGN_MASK 15UL
#define MEMPOOL_RESERVED ((sizeof(struct mempool)+ALIGN_MASK) & ~ALIGN_MASK)
struct mempool {
unsigned int used, size;
void* (*malloc)(size_t);
void (*free)(void*);
struct mempool *next;
};
LIQ_PRIVATE void* mempool_create(mempool *mptr, const unsigned int size, unsigned int max_size, void* (*malloc)(size_t), void (*free)(void*))
{
if (*mptr && ((*mptr)->used+size) <= (*mptr)->size) {
unsigned int prevused = (*mptr)->used;
(*mptr)->used += (size+15UL) & ~0xFUL;
return ((char*)(*mptr)) + prevused;
}
mempool old = *mptr;
if (!max_size) max_size = (1<<17);
max_size = size+ALIGN_MASK > max_size ? size+ALIGN_MASK : max_size;
*mptr = malloc(MEMPOOL_RESERVED + max_size);
if (!*mptr) return NULL;
**mptr = (struct mempool){
.malloc = malloc,
.free = free,
.size = MEMPOOL_RESERVED + max_size,
.used = sizeof(struct mempool),
.next = old,
};
uintptr_t mptr_used_start = (uintptr_t)(*mptr) + (*mptr)->used;
(*mptr)->used += (ALIGN_MASK + 1 - (mptr_used_start & ALIGN_MASK)) & ALIGN_MASK; // reserve bytes required to make subsequent allocations aligned
assert(!(((uintptr_t)(*mptr) + (*mptr)->used) & ALIGN_MASK));
return mempool_alloc(mptr, size, size);
}
LIQ_PRIVATE void* mempool_alloc(mempool *mptr, const unsigned int size, const unsigned int max_size)
{
if (((*mptr)->used+size) <= (*mptr)->size) {
unsigned int prevused = (*mptr)->used;
(*mptr)->used += (size + ALIGN_MASK) & ~ALIGN_MASK;
return ((char*)(*mptr)) + prevused;
}
return mempool_create(mptr, size, max_size, (*mptr)->malloc, (*mptr)->free);
}
LIQ_PRIVATE void mempool_destroy(mempool m)
{
while (m) {
mempool next = m->next;
m->free(m);
m = next;
}
}

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#ifndef MEMPOOL_H
#define MEMPOOL_H
#include <stddef.h>
struct mempool;
typedef struct mempool *mempool;
LIQ_PRIVATE void* mempool_create(mempool *mptr, const unsigned int size, unsigned int capacity, void* (*malloc)(size_t), void (*free)(void*));
LIQ_PRIVATE void* mempool_alloc(mempool *mptr, const unsigned int size, const unsigned int capacity);
LIQ_PRIVATE void mempool_destroy(mempool m);
#endif

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/*
© 2011-2015 by Kornel Lesiński.
This file is part of libimagequant.
libimagequant is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
libimagequant is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with libimagequant. If not, see <http://www.gnu.org/licenses/>.
*/
#include "libimagequant.h"
#include "pam.h"
#include "nearest.h"
#include "mempool.h"
#include <stdlib.h>
typedef struct vp_sort_tmp {
float distance_squared;
unsigned int idx;
} vp_sort_tmp;
typedef struct vp_search_tmp {
float distance;
unsigned int idx;
int exclude;
} vp_search_tmp;
typedef struct vp_node {
struct vp_node *near, *far;
f_pixel vantage_point;
float radius;
unsigned int idx;
} vp_node;
struct nearest_map {
vp_node *root;
const colormap_item *palette;
float nearest_other_color_dist[256];
mempool mempool;
};
static void vp_search_node(const vp_node *node, const f_pixel *const needle, vp_search_tmp *const best_candidate);
static int vp_compare_distance(const void *ap, const void *bp) {
float a = ((const vp_sort_tmp*)ap)->distance_squared;
float b = ((const vp_sort_tmp*)bp)->distance_squared;
return a > b ? 1 : -1;
}
static void vp_sort_indexes_by_distance(const f_pixel vantage_point, vp_sort_tmp *indexes, int num_indexes, const colormap_item items[]) {
for(int i=0; i < num_indexes; i++) {
indexes[i].distance_squared = colordifference(vantage_point, items[indexes[i].idx].acolor);
}
qsort(indexes, num_indexes, sizeof(indexes[0]), vp_compare_distance);
}
/*
* Usually it should pick farthest point, but picking most popular point seems to make search quicker anyway
*/
static int vp_find_best_vantage_point_index(vp_sort_tmp *indexes, int num_indexes, const colormap_item items[]) {
int best = 0;
float best_popularity = items[indexes[0].idx].popularity;
for(int i = 1; i < num_indexes; i++) {
if (items[indexes[i].idx].popularity > best_popularity) {
best_popularity = items[indexes[i].idx].popularity;
best = i;
}
}
return best;
}
static vp_node *vp_create_node(mempool *m, vp_sort_tmp *indexes, int num_indexes, const colormap_item items[]) {
if (num_indexes <= 0) {
return NULL;
}
vp_node *node = mempool_alloc(m, sizeof(node[0]), 0);
if (num_indexes == 1) {
*node = (vp_node){
.vantage_point = items[indexes[0].idx].acolor,
.idx = indexes[0].idx,
.radius = MAX_DIFF,
};
return node;
}
const int ref = vp_find_best_vantage_point_index(indexes, num_indexes, items);
const int ref_idx = indexes[ref].idx;
// Removes the `ref_idx` item from remaining items, because it's included in the current node
num_indexes -= 1;
indexes[ref] = indexes[num_indexes];
vp_sort_indexes_by_distance(items[ref_idx].acolor, indexes, num_indexes, items);
// Remaining items are split by the median distance
const int half_idx = num_indexes/2;
*node = (vp_node){
.vantage_point = items[ref_idx].acolor,
.idx = ref_idx,
.radius = sqrtf(indexes[half_idx].distance_squared),
};
node->near = vp_create_node(m, indexes, half_idx, items);
node->far = vp_create_node(m, &indexes[half_idx], num_indexes - half_idx, items);
return node;
}
LIQ_PRIVATE struct nearest_map *nearest_init(const colormap *map, const bool fast) {
mempool m = NULL;
struct nearest_map *handle = mempool_create(&m, sizeof(handle[0]), sizeof(handle[0]) + sizeof(vp_node)*map->colors+16, map->malloc, map->free);
vp_sort_tmp indexes[map->colors];
for(unsigned int i=0; i < map->colors; i++) {
indexes[i].idx = i;
}
vp_node *root = vp_create_node(&m, indexes, map->colors, map->palette);
*handle = (struct nearest_map){
.root = root,
.palette = map->palette,
.mempool = m,
};
for(unsigned int i=0; i < map->colors; i++) {
vp_search_tmp best = {
.distance = MAX_DIFF,
.exclude = i,
};
vp_search_node(root, &map->palette[i].acolor, &best);
handle->nearest_other_color_dist[i] = best.distance * best.distance / 4.0; // half of squared distance
}
return handle;
}
static void vp_search_node(const vp_node *node, const f_pixel *const needle, vp_search_tmp *const best_candidate) {
do {
const float distance = sqrtf(colordifference(node->vantage_point, *needle));
if (distance < best_candidate->distance && best_candidate->exclude != node->idx) {
best_candidate->distance = distance;
best_candidate->idx = node->idx;
}
// Recurse towards most likely candidate first to narrow best candidate's distance as soon as possible
if (distance < node->radius) {
if (node->near) {
vp_search_node(node->near, needle, best_candidate);
}
// The best node (final answer) may be just ouside the radius, but not farther than
// the best distance we know so far. The vp_search_node above should have narrowed
// best_candidate->distance, so this path is rarely taken.
if (node->far && distance >= node->radius - best_candidate->distance) {
node = node->far; // Fast tail recursion
} else {
break;
}
} else {
if (node->far) {
vp_search_node(node->far, needle, best_candidate);
}
if (node->near && distance <= node->radius + best_candidate->distance) {
node = node->near; // Fast tail recursion
} else {
break;
}
}
} while(true);
}
LIQ_PRIVATE unsigned int nearest_search(const struct nearest_map *handle, const f_pixel *px, const int likely_colormap_index, float *diff) {
const float guess_diff = colordifference(handle->palette[likely_colormap_index].acolor, *px);
if (guess_diff < handle->nearest_other_color_dist[likely_colormap_index]) {
if (diff) *diff = guess_diff;
return likely_colormap_index;
}
vp_search_tmp best_candidate = {
.distance = sqrtf(guess_diff),
.idx = likely_colormap_index,
.exclude = -1,
};
vp_search_node(handle->root, px, &best_candidate);
if (diff) {
*diff = best_candidate.distance * best_candidate.distance;
}
return best_candidate.idx;
}
LIQ_PRIVATE void nearest_free(struct nearest_map *centroids)
{
mempool_destroy(centroids->mempool);
}

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//
// nearest.h
// pngquant
//
struct nearest_map;
LIQ_PRIVATE struct nearest_map *nearest_init(const colormap *palette, const bool fast);
LIQ_PRIVATE unsigned int nearest_search(const struct nearest_map *map, const f_pixel *px, const int palette_index_guess, float *diff);
LIQ_PRIVATE void nearest_free(struct nearest_map *map);

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/* pam.c - pam (portable alpha map) utility library
**
** Copyright (C) 1989, 1991 by Jef Poskanzer.
** Copyright (C) 1997, 2000, 2002 by Greg Roelofs; based on an idea by
** Stefan Schneider.
** © 2009-2016 by Kornel Lesinski.
**
** Permission to use, copy, modify, and distribute this software and its
** documentation for any purpose and without fee is hereby granted, provided
** that the above copyright notice appear in all copies and that both that
** copyright notice and this permission notice appear in supporting
** documentation. This software is provided "as is" without express or
** implied warranty.
*/
#include <stdlib.h>
#include <string.h>
#include "libimagequant.h"
#include "pam.h"
#include "mempool.h"
LIQ_PRIVATE bool pam_computeacolorhash(struct acolorhash_table *acht, const rgba_pixel *const pixels[], unsigned int cols, unsigned int rows, const unsigned char *importance_map)
{
const unsigned int maxacolors = acht->maxcolors, ignorebits = acht->ignorebits;
const unsigned int channel_mask = 255U>>ignorebits<<ignorebits;
const unsigned int channel_hmask = (255U>>ignorebits) ^ 0xFFU;
const unsigned int posterize_mask = channel_mask << 24 | channel_mask << 16 | channel_mask << 8 | channel_mask;
const unsigned int posterize_high_mask = channel_hmask << 24 | channel_hmask << 16 | channel_hmask << 8 | channel_hmask;
struct acolorhist_arr_head *const buckets = acht->buckets;
unsigned int colors = acht->colors;
const unsigned int hash_size = acht->hash_size;
const unsigned int stacksize = sizeof(acht->freestack)/sizeof(acht->freestack[0]);
struct acolorhist_arr_item **freestack = acht->freestack;
unsigned int freestackp=acht->freestackp;
/* Go through the entire image, building a hash table of colors. */
for(unsigned int row = 0; row < rows; ++row) {
float boost=1.0;
for(unsigned int col = 0; col < cols; ++col) {
if (importance_map) {
boost = 0.5f+ (double)*importance_map++/255.f;
}
// RGBA color is casted to long for easier hasing/comparisons
union rgba_as_int px = {pixels[row][col]};
unsigned int hash;
if (!px.rgba.a) {
// "dirty alpha" has different RGBA values that end up being the same fully transparent color
px.l=0; hash=0;
boost = 10;
} else {
// mask posterizes all 4 channels in one go
px.l = (px.l & posterize_mask) | ((px.l & posterize_high_mask) >> (8-ignorebits));
// fancier hashing algorithms didn't improve much
hash = px.l % hash_size;
}
/* head of the hash function stores first 2 colors inline (achl->used = 1..2),
to reduce number of allocations of achl->other_items.
*/
struct acolorhist_arr_head *achl = &buckets[hash];
if (achl->inline1.color.l == px.l && achl->used) {
achl->inline1.perceptual_weight += boost;
continue;
}
if (achl->used) {
if (achl->used > 1) {
if (achl->inline2.color.l == px.l) {
achl->inline2.perceptual_weight += boost;
continue;
}
// other items are stored as an array (which gets reallocated if needed)
struct acolorhist_arr_item *other_items = achl->other_items;
unsigned int i = 0;
for (; i < achl->used-2; i++) {
if (other_items[i].color.l == px.l) {
other_items[i].perceptual_weight += boost;
goto continue_outer_loop;
}
}
// the array was allocated with spare items
if (i < achl->capacity) {
other_items[i] = (struct acolorhist_arr_item){
.color = px,
.perceptual_weight = boost,
};
achl->used++;
++colors;
continue;
}
if (++colors > maxacolors) {
acht->colors = colors;
acht->freestackp = freestackp;
return false;
}
struct acolorhist_arr_item *new_items;
unsigned int capacity;
if (!other_items) { // there was no array previously, alloc "small" array
capacity = 8;
if (freestackp <= 0) {
// estimate how many colors are going to be + headroom
const size_t mempool_size = ((acht->rows + rows-row) * 2 * colors / (acht->rows + row + 1) + 1024) * sizeof(struct acolorhist_arr_item);
new_items = mempool_alloc(&acht->mempool, sizeof(struct acolorhist_arr_item)*capacity, mempool_size);
} else {
// freestack stores previously freed (reallocated) arrays that can be reused
// (all pesimistically assumed to be capacity = 8)
new_items = freestack[--freestackp];
}
} else {
// simply reallocs and copies array to larger capacity
capacity = achl->capacity*2 + 16;
if (freestackp < stacksize-1) {
freestack[freestackp++] = other_items;
}
const size_t mempool_size = ((acht->rows + rows-row) * 2 * colors / (acht->rows + row + 1) + 32*capacity) * sizeof(struct acolorhist_arr_item);
new_items = mempool_alloc(&acht->mempool, sizeof(struct acolorhist_arr_item)*capacity, mempool_size);
if (!new_items) return false;
memcpy(new_items, other_items, sizeof(other_items[0])*achl->capacity);
}
achl->other_items = new_items;
achl->capacity = capacity;
new_items[i] = (struct acolorhist_arr_item){
.color = px,
.perceptual_weight = boost,
};
achl->used++;
} else {
// these are elses for first checks whether first and second inline-stored colors are used
achl->inline2.color.l = px.l;
achl->inline2.perceptual_weight = boost;
achl->used = 2;
++colors;
}
} else {
achl->inline1.color.l = px.l;
achl->inline1.perceptual_weight = boost;
achl->used = 1;
++colors;
}
continue_outer_loop:;
}
}
acht->colors = colors;
acht->cols = cols;
acht->rows += rows;
acht->freestackp = freestackp;
return true;
}
LIQ_PRIVATE struct acolorhash_table *pam_allocacolorhash(unsigned int maxcolors, unsigned int surface, unsigned int ignorebits, void* (*malloc)(size_t), void (*free)(void*))
{
const size_t estimated_colors = MIN(maxcolors, surface/(ignorebits + (surface > 512*512 ? 6 : 5)));
const size_t hash_size = estimated_colors < 66000 ? 6673 : (estimated_colors < 200000 ? 12011 : 24019);
mempool m = NULL;
const size_t buckets_size = hash_size * sizeof(struct acolorhist_arr_head);
const size_t mempool_size = sizeof(struct acolorhash_table) + buckets_size + estimated_colors * sizeof(struct acolorhist_arr_item);
struct acolorhash_table *t = mempool_create(&m, sizeof(*t) + buckets_size, mempool_size, malloc, free);
if (!t) return NULL;
*t = (struct acolorhash_table){
.mempool = m,
.hash_size = hash_size,
.maxcolors = maxcolors,
.ignorebits = ignorebits,
};
memset(t->buckets, 0, buckets_size);
return t;
}
#define PAM_ADD_TO_HIST(entry) { \
hist->achv[j].acolor = to_f(gamma_lut, entry.color.rgba); \
total_weight += hist->achv[j].adjusted_weight = hist->achv[j].perceptual_weight = MIN(entry.perceptual_weight, max_perceptual_weight); \
++j; \
}
LIQ_PRIVATE histogram *pam_acolorhashtoacolorhist(const struct acolorhash_table *acht, const double gamma, void* (*malloc)(size_t), void (*free)(void*))
{
histogram *hist = malloc(sizeof(hist[0]));
if (!hist || !acht) return NULL;
*hist = (histogram){
.achv = malloc(MAX(1,acht->colors) * sizeof(hist->achv[0])),
.size = acht->colors,
.free = free,
.ignorebits = acht->ignorebits,
};
if (!hist->achv) return NULL;
float gamma_lut[256];
to_f_set_gamma(gamma_lut, gamma);
/* Limit perceptual weight to 1/10th of the image surface area to prevent
a single color from dominating all others. */
float max_perceptual_weight = 0.1f * acht->cols * acht->rows;
double total_weight = 0;
for(unsigned int j=0, i=0; i < acht->hash_size; ++i) {
const struct acolorhist_arr_head *const achl = &acht->buckets[i];
if (achl->used) {
PAM_ADD_TO_HIST(achl->inline1);
if (achl->used > 1) {
PAM_ADD_TO_HIST(achl->inline2);
for(unsigned int k=0; k < achl->used-2; k++) {
PAM_ADD_TO_HIST(achl->other_items[k]);
}
}
}
}
hist->total_perceptual_weight = total_weight;
return hist;
}
LIQ_PRIVATE void pam_freeacolorhash(struct acolorhash_table *acht)
{
if (acht) {
mempool_destroy(acht->mempool);
}
}
LIQ_PRIVATE void pam_freeacolorhist(histogram *hist)
{
hist->free(hist->achv);
hist->free(hist);
}
LIQ_PRIVATE colormap *pam_colormap(unsigned int colors, void* (*malloc)(size_t), void (*free)(void*))
{
assert(colors > 0 && colors < 65536);
colormap *map;
const size_t colors_size = colors * sizeof(map->palette[0]);
map = malloc(sizeof(colormap) + colors_size);
if (!map) return NULL;
*map = (colormap){
.malloc = malloc,
.free = free,
.colors = colors,
};
memset(map->palette, 0, colors_size);
return map;
}
LIQ_PRIVATE colormap *pam_duplicate_colormap(colormap *map)
{
colormap *dupe = pam_colormap(map->colors, map->malloc, map->free);
for(unsigned int i=0; i < map->colors; i++) {
dupe->palette[i] = map->palette[i];
}
return dupe;
}
LIQ_PRIVATE void pam_freecolormap(colormap *c)
{
c->free(c);
}
LIQ_PRIVATE void to_f_set_gamma(float gamma_lut[], const double gamma)
{
for(int i=0; i < 256; i++) {
gamma_lut[i] = pow((double)i/255.0, internal_gamma/gamma);
}
}

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/* pam.h - pam (portable alpha map) utility library
**
** Colormap routines.
**
** Copyright (C) 1989, 1991 by Jef Poskanzer.
** Copyright (C) 1997 by Greg Roelofs.
**
** Permission to use, copy, modify, and distribute this software and its
** documentation for any purpose and without fee is hereby granted, provided
** that the above copyright notice appear in all copies and that both that
** copyright notice and this permission notice appear in supporting
** documentation. This software is provided "as is" without express or
** implied warranty.
*/
#ifndef PAM_H
#define PAM_H
#include <math.h>
#include <assert.h>
#include <stdlib.h>
#include <stdbool.h>
#ifndef MAX
# define MAX(a,b) ((a) > (b)? (a) : (b))
# define MIN(a,b) ((a) < (b)? (a) : (b))
#endif
#define MAX_DIFF 1e20
#ifndef USE_SSE
# if defined(__SSE__) && (defined(__amd64__) || defined(__X86_64__) || defined(_WIN64) || defined(WIN32) || defined(__WIN32__))
# define USE_SSE 1
# else
# define USE_SSE 0
# endif
#endif
#if USE_SSE
# include <xmmintrin.h>
# ifdef _MSC_VER
# include <intrin.h>
# define SSE_ALIGN
# else
# define SSE_ALIGN __attribute__ ((aligned (16)))
# if defined(__i386__) && defined(__PIC__)
# define cpuid(func,ax,bx,cx,dx)\
__asm__ __volatile__ ( \
"push %%ebx\n" \
"cpuid\n" \
"mov %%ebx, %1\n" \
"pop %%ebx\n" \
: "=a" (ax), "=r" (bx), "=c" (cx), "=d" (dx) \
: "a" (func));
# else
# define cpuid(func,ax,bx,cx,dx)\
__asm__ __volatile__ ("cpuid":\
"=a" (ax), "=b" (bx), "=c" (cx), "=d" (dx) : "a" (func));
# endif
#endif
#else
# define SSE_ALIGN
#endif
#if defined(__GNUC__) || defined (__llvm__)
#define ALWAYS_INLINE __attribute__((always_inline)) inline
#define NEVER_INLINE __attribute__ ((noinline))
#elif defined(_MSC_VER)
#define inline __inline
#define restrict __restrict
#define ALWAYS_INLINE __forceinline
#define NEVER_INLINE __declspec(noinline)
#else
#define ALWAYS_INLINE inline
#define NEVER_INLINE
#endif
/* from pam.h */
typedef struct {
unsigned char r, g, b, a;
} rgba_pixel;
typedef struct {
float a, r, g, b;
} SSE_ALIGN f_pixel;
static const double internal_gamma = 0.5499;
LIQ_PRIVATE void to_f_set_gamma(float gamma_lut[], const double gamma);
/**
Converts 8-bit color to internal gamma and premultiplied alpha.
(premultiplied color space is much better for blending of semitransparent colors)
*/
ALWAYS_INLINE static f_pixel to_f(const float gamma_lut[], const rgba_pixel px);
inline static f_pixel to_f(const float gamma_lut[], const rgba_pixel px)
{
float a = px.a/255.f;
return (f_pixel) {
.a = a,
.r = gamma_lut[px.r]*a,
.g = gamma_lut[px.g]*a,
.b = gamma_lut[px.b]*a,
};
}
inline static rgba_pixel to_rgb(const float gamma, const f_pixel px)
{
if (px.a < 1.f/256.f) {
return (rgba_pixel){0,0,0,0};
}
float r = px.r / px.a,
g = px.g / px.a,
b = px.b / px.a,
a = px.a;
r = powf(r, gamma/internal_gamma);
g = powf(g, gamma/internal_gamma);
b = powf(b, gamma/internal_gamma);
// 256, because numbers are in range 1..255.9999… rounded down
r *= 256.f;
g *= 256.f;
b *= 256.f;
a *= 256.f;
return (rgba_pixel){
.r = r>=255.f ? 255 : r,
.g = g>=255.f ? 255 : g,
.b = b>=255.f ? 255 : b,
.a = a>=255.f ? 255 : a,
};
}
ALWAYS_INLINE static double colordifference_ch(const double x, const double y, const double alphas);
inline static double colordifference_ch(const double x, const double y, const double alphas)
{
// maximum of channel blended on white, and blended on black
// premultiplied alpha and backgrounds 0/1 shorten the formula
const double black = x-y, white = black+alphas;
return MAX(black*black, white*white);
}
ALWAYS_INLINE static float colordifference_stdc(const f_pixel px, const f_pixel py);
inline static float colordifference_stdc(const f_pixel px, const f_pixel py)
{
// px_b.rgb = px.rgb + 0*(1-px.a) // blend px on black
// px_b.a = px.a + 1*(1-px.a)
// px_w.rgb = px.rgb + 1*(1-px.a) // blend px on white
// px_w.a = px.a + 1*(1-px.a)
// px_b.rgb = px.rgb // difference same as in opaque RGB
// px_b.a = 1
// px_w.rgb = px.rgb - px.a // difference simplifies to formula below
// px_w.a = 1
// (px.rgb - px.a) - (py.rgb - py.a)
// (px.rgb - py.rgb) + (py.a - px.a)
const double alphas = py.a-px.a;
return colordifference_ch(px.r, py.r, alphas) +
colordifference_ch(px.g, py.g, alphas) +
colordifference_ch(px.b, py.b, alphas);
}
ALWAYS_INLINE static float colordifference(f_pixel px, f_pixel py);
inline static float colordifference(f_pixel px, f_pixel py)
{
#if USE_SSE
const __m128 vpx = _mm_load_ps((const float*)&px);
const __m128 vpy = _mm_load_ps((const float*)&py);
// y.a - x.a
__m128 alphas = _mm_sub_ss(vpy, vpx);
alphas = _mm_shuffle_ps(alphas,alphas,0); // copy first to all four
__m128 onblack = _mm_sub_ps(vpx, vpy); // x - y
__m128 onwhite = _mm_add_ps(onblack, alphas); // x - y + (y.a - x.a)
onblack = _mm_mul_ps(onblack, onblack);
onwhite = _mm_mul_ps(onwhite, onwhite);
const __m128 max = _mm_max_ps(onwhite, onblack);
// add rgb, not a
const __m128 maxhl = _mm_movehl_ps(max, max);
const __m128 tmp = _mm_add_ps(max, maxhl);
const __m128 sum = _mm_add_ss(maxhl, _mm_shuffle_ps(tmp, tmp, 1));
const float res = _mm_cvtss_f32(sum);
assert(fabs(res - colordifference_stdc(px,py)) < 0.001);
return res;
#else
return colordifference_stdc(px,py);
#endif
}
/* from pamcmap.h */
union rgba_as_int {
rgba_pixel rgba;
unsigned int l;
};
typedef struct {
f_pixel acolor;
float adjusted_weight, // perceptual weight changed to tweak how mediancut selects colors
perceptual_weight; // number of pixels weighted by importance of different areas of the picture
float color_weight; // these two change every time histogram subset is sorted
union {
unsigned int sort_value;
unsigned char likely_colormap_index;
} tmp;
} hist_item;
typedef struct {
hist_item *achv;
void (*free)(void*);
double total_perceptual_weight;
unsigned int size;
unsigned int ignorebits;
} histogram;
typedef struct {
f_pixel acolor;
float popularity;
bool fixed; // if true it's user-supplied and must not be changed (e.g in voronoi iteration)
} colormap_item;
typedef struct colormap {
unsigned int colors;
void* (*malloc)(size_t);
void (*free)(void*);
colormap_item palette[];
} colormap;
struct acolorhist_arr_item {
union rgba_as_int color;
float perceptual_weight;
};
struct acolorhist_arr_head {
struct acolorhist_arr_item inline1, inline2;
unsigned int used, capacity;
struct acolorhist_arr_item *other_items;
};
struct acolorhash_table {
struct mempool *mempool;
unsigned int ignorebits, maxcolors, colors, cols, rows;
unsigned int hash_size;
unsigned int freestackp;
struct acolorhist_arr_item *freestack[512];
struct acolorhist_arr_head buckets[];
};
LIQ_PRIVATE void pam_freeacolorhash(struct acolorhash_table *acht);
LIQ_PRIVATE struct acolorhash_table *pam_allocacolorhash(unsigned int maxcolors, unsigned int surface, unsigned int ignorebits, void* (*malloc)(size_t), void (*free)(void*));
LIQ_PRIVATE histogram *pam_acolorhashtoacolorhist(const struct acolorhash_table *acht, const double gamma, void* (*malloc)(size_t), void (*free)(void*));
LIQ_PRIVATE bool pam_computeacolorhash(struct acolorhash_table *acht, const rgba_pixel *const pixels[], unsigned int cols, unsigned int rows, const unsigned char *importance_map);
LIQ_PRIVATE void pam_freeacolorhist(histogram *h);
LIQ_PRIVATE colormap *pam_colormap(unsigned int colors, void* (*malloc)(size_t), void (*free)(void*));
LIQ_PRIVATE colormap *pam_duplicate_colormap(colormap *map);
LIQ_PRIVATE void pam_freecolormap(colormap *c);
#endif

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/*
© 2011-2016 by Kornel Lesiński.
This file is part of libimagequant.
libimagequant is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
libimagequant is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with libimagequant. If not, see <http://www.gnu.org/licenses/>.
*/
#include "libimagequant.h"
#include "pam.h"
#include "viter.h"
#include "nearest.h"
#include <stdlib.h>
#include <string.h>
#ifdef _OPENMP
#include <omp.h>
#else
#define omp_get_max_threads() 1
#define omp_get_thread_num() 0
#endif
/*
* Voronoi iteration: new palette color is computed from weighted average of colors that map to that palette entry.
*/
LIQ_PRIVATE void viter_init(const colormap *map, const unsigned int max_threads, viter_state average_color[])
{
memset(average_color, 0, sizeof(average_color[0])*(VITER_CACHE_LINE_GAP+map->colors)*max_threads);
}
LIQ_PRIVATE void viter_update_color(const f_pixel acolor, const float value, const colormap *map, unsigned int match, const unsigned int thread, viter_state average_color[])
{
match += thread * (VITER_CACHE_LINE_GAP+map->colors);
average_color[match].a += acolor.a * value;
average_color[match].r += acolor.r * value;
average_color[match].g += acolor.g * value;
average_color[match].b += acolor.b * value;
average_color[match].total += value;
}
LIQ_PRIVATE void viter_finalize(colormap *map, const unsigned int max_threads, const viter_state average_color[])
{
for (unsigned int i=0; i < map->colors; i++) {
double a=0, r=0, g=0, b=0, total=0;
// Aggregate results from all threads
for(unsigned int t=0; t < max_threads; t++) {
const unsigned int offset = (VITER_CACHE_LINE_GAP+map->colors) * t + i;
a += average_color[offset].a;
r += average_color[offset].r;
g += average_color[offset].g;
b += average_color[offset].b;
total += average_color[offset].total;
}
if (total && !map->palette[i].fixed) {
map->palette[i].acolor = (f_pixel){
.a = a / total,
.r = r / total,
.g = g / total,
.b = b / total,
};
map->palette[i].popularity = total;
}
}
}
LIQ_PRIVATE double viter_do_iteration(histogram *hist, colormap *const map, viter_callback callback, const bool fast_palette)
{
const unsigned int max_threads = omp_get_max_threads();
viter_state average_color[(VITER_CACHE_LINE_GAP+map->colors) * max_threads];
viter_init(map, max_threads, average_color);
struct nearest_map *const n = nearest_init(map, fast_palette);
hist_item *const achv = hist->achv;
const int hist_size = hist->size;
double total_diff=0;
#pragma omp parallel for if (hist_size > 3000) \
schedule(static) default(none) shared(average_color,callback) reduction(+:total_diff)
for(int j=0; j < hist_size; j++) {
float diff;
unsigned int match = nearest_search(n, &achv[j].acolor, achv[j].tmp.likely_colormap_index, &diff);
achv[j].tmp.likely_colormap_index = match;
total_diff += diff * achv[j].perceptual_weight;
viter_update_color(achv[j].acolor, achv[j].perceptual_weight, map, match, omp_get_thread_num(), average_color);
if (callback) callback(&achv[j], diff);
}
nearest_free(n);
viter_finalize(map, max_threads, average_color);
return total_diff / hist->total_perceptual_weight;
}

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#ifndef VITER_H
#define VITER_H
// Spread memory touched by different threads at least 64B apart which I assume is the cache line size. This should avoid memory write contention.
#define VITER_CACHE_LINE_GAP ((64+sizeof(viter_state)-1)/sizeof(viter_state))
typedef struct {
double a, r, g, b, total;
} viter_state;
typedef void (*viter_callback)(hist_item *item, float diff);
LIQ_PRIVATE void viter_init(const colormap *map, const unsigned int max_threads, viter_state state[]);
LIQ_PRIVATE void viter_update_color(const f_pixel acolor, const float value, const colormap *map, unsigned int match, const unsigned int thread, viter_state average_color[]);
LIQ_PRIVATE void viter_finalize(colormap *map, const unsigned int max_threads, const viter_state state[]);
LIQ_PRIVATE double viter_do_iteration(histogram *hist, colormap *const map, viter_callback callback, const bool fast_palette);
#endif