imagequant/pam.c

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/* pam.c - pam (portable alpha map) utility library
**
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** © 2009-2017 by Kornel Lesiński.
** © 1989, 1991 by Jef Poskanzer.
** © 1997, 2000, 2002 by Greg Roelofs; based on an idea by Stefan Schneider.
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**
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** See COPYRIGHT file for license.
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*/
#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 ignorebits = acht->ignorebits;
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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;
const unsigned int hash_size = acht->hash_size;
/* Go through the entire image, building a hash table of colors. */
for(unsigned int row = 0; row < rows; ++row) {
for(unsigned int col = 0; col < cols; ++col) {
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unsigned int boost;
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// 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;
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boost = 2000;
if (importance_map) {
importance_map++;
}
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} 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;
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if (importance_map) {
boost = *importance_map++;
} else {
boost = 255;
}
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}
if (!pam_add_to_hash(acht, hash, boost, px, row, rows)) {
return false;
}
}
}
acht->cols = cols;
acht->rows += rows;
return true;
}
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LIQ_PRIVATE bool pam_add_to_hash(struct acolorhash_table *acht, unsigned int hash, unsigned int boost, union rgba_as_int px, unsigned int row, unsigned int rows)
{
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/* 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 = &acht->buckets[hash];
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if (achl->inline1.color.l == px.l && achl->used) {
achl->inline1.perceptual_weight += boost;
return true;
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}
if (achl->used) {
if (achl->used > 1) {
if (achl->inline2.color.l == px.l) {
achl->inline2.perceptual_weight += boost;
return true;
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}
// 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;
return true;
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}
}
// 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++;
++acht->colors;
return true;
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}
if (++acht->colors > acht->maxcolors) {
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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 (acht->freestackp <= 0) {
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// estimate how many colors are going to be + headroom
const size_t mempool_size = ((acht->rows + rows-row) * 2 * acht->colors / (acht->rows + row + 1) + 1024) * sizeof(struct acolorhist_arr_item);
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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 = acht->freestack[--acht->freestackp];
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}
} else {
const unsigned int stacksize = sizeof(acht->freestack)/sizeof(acht->freestack[0]);
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// simply reallocs and copies array to larger capacity
capacity = achl->capacity*2 + 16;
if (acht->freestackp < stacksize-1) {
acht->freestack[acht->freestackp++] = other_items;
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}
const size_t mempool_size = ((acht->rows + rows-row) * 2 * acht->colors / (acht->rows + row + 1) + 32*capacity) * sizeof(struct acolorhist_arr_item);
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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;
++acht->colors;
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}
} else {
achl->inline1.color.l = px.l;
achl->inline1.perceptual_weight = boost;
achl->used = 1;
++acht->colors;
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}
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);
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mempoolptr m = NULL;
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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;
}
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ALWAYS_INLINE static float pam_add_to_hist(const float *gamma_lut, hist_item *achv, unsigned int *j, const struct acolorhist_arr_item *entry, const float max_perceptual_weight)
{
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if (entry->perceptual_weight == 0) {
return 0;
}
const float w = MIN(entry->perceptual_weight/128.f, max_perceptual_weight);
achv[*j].adjusted_weight = achv[*j].perceptual_weight = w;
achv[*j].acolor = rgba_to_f(gamma_lut, entry->color.rgba);
*j += 1;
return w;
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}
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;
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unsigned int j=0;
for(unsigned int i=0; i < acht->hash_size; ++i) {
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const struct acolorhist_arr_head *const achl = &acht->buckets[i];
if (achl->used) {
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total_weight += pam_add_to_hist(gamma_lut, hist->achv, &j, &achl->inline1, max_perceptual_weight);
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if (achl->used > 1) {
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total_weight += pam_add_to_hist(gamma_lut, hist->achv, &j, &achl->inline2, max_perceptual_weight);
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for(unsigned int k=0; k < achl->used-2; k++) {
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total_weight += pam_add_to_hist(gamma_lut, hist->achv, &j, &achl->other_items[k], max_perceptual_weight);
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}
}
}
}
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hist->size = j;
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hist->total_perceptual_weight = total_weight;
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for(unsigned int k=0; k < hist->size; k++) {
hist->achv[k].tmp.likely_colormap_index = 0;
}
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if (!j) {
pam_freeacolorhist(hist);
return NULL;
}
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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);
}
}