287 lines
11 KiB
C
287 lines
11 KiB
C
/* pam.c - pam (portable alpha map) utility library
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**
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** © 2009-2017 by Kornel Lesiński.
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** © 1989, 1991 by Jef Poskanzer.
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** © 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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*/
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#include <stdlib.h>
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#include <string.h>
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#include "libimagequant.h"
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#include "pam.h"
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#include "mempool.h"
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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)
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{
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const unsigned int ignorebits = acht->ignorebits;
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const unsigned int channel_mask = 255U>>ignorebits<<ignorebits;
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const unsigned int channel_hmask = (255U>>ignorebits) ^ 0xFFU;
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const unsigned int posterize_mask = channel_mask << 24 | channel_mask << 16 | channel_mask << 8 | channel_mask;
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const unsigned int posterize_high_mask = channel_hmask << 24 | channel_hmask << 16 | channel_hmask << 8 | channel_hmask;
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const unsigned int hash_size = acht->hash_size;
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/* Go through the entire image, building a hash table of colors. */
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for(unsigned int row = 0; row < rows; ++row) {
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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
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union rgba_as_int px = {pixels[row][col]};
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unsigned int hash;
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if (!px.rgba.a) {
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// "dirty alpha" has different RGBA values that end up being the same fully transparent color
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px.l=0; hash=0;
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boost = 2000;
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if (importance_map) {
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importance_map++;
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}
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} else {
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// mask posterizes all 4 channels in one go
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px.l = (px.l & posterize_mask) | ((px.l & posterize_high_mask) >> (8-ignorebits));
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// fancier hashing algorithms didn't improve much
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hash = px.l % hash_size;
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if (importance_map) {
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boost = *importance_map++;
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} else {
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boost = 255;
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}
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}
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if (!pam_add_to_hash(acht, hash, boost, px, row, rows)) {
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return false;
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}
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}
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}
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acht->cols = cols;
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acht->rows += rows;
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return true;
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}
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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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{
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/* head of the hash function stores first 2 colors inline (achl->used = 1..2),
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to reduce number of allocations of achl->other_items.
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*/
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struct acolorhist_arr_head *achl = &acht->buckets[hash];
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if (achl->inline1.color.l == px.l && achl->used) {
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achl->inline1.perceptual_weight += boost;
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return true;
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}
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if (achl->used) {
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if (achl->used > 1) {
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if (achl->inline2.color.l == px.l) {
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achl->inline2.perceptual_weight += boost;
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return true;
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}
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// other items are stored as an array (which gets reallocated if needed)
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struct acolorhist_arr_item *other_items = achl->other_items;
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unsigned int i = 0;
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for (; i < achl->used-2; i++) {
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if (other_items[i].color.l == px.l) {
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other_items[i].perceptual_weight += boost;
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return true;
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}
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}
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// the array was allocated with spare items
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if (i < achl->capacity) {
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other_items[i] = (struct acolorhist_arr_item){
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.color = px,
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.perceptual_weight = boost,
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};
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achl->used++;
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++acht->colors;
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return true;
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}
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if (++acht->colors > acht->maxcolors) {
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return false;
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}
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struct acolorhist_arr_item *new_items;
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unsigned int capacity;
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if (!other_items) { // there was no array previously, alloc "small" array
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capacity = 8;
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if (acht->freestackp <= 0) {
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// estimate how many colors are going to be + headroom
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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);
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} else {
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// freestack stores previously freed (reallocated) arrays that can be reused
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// (all pesimistically assumed to be capacity = 8)
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new_items = acht->freestack[--acht->freestackp];
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}
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} else {
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const unsigned int stacksize = sizeof(acht->freestack)/sizeof(acht->freestack[0]);
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// simply reallocs and copies array to larger capacity
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capacity = achl->capacity*2 + 16;
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if (acht->freestackp < stacksize-1) {
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acht->freestack[acht->freestackp++] = other_items;
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}
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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);
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if (!new_items) return false;
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memcpy(new_items, other_items, sizeof(other_items[0])*achl->capacity);
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}
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achl->other_items = new_items;
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achl->capacity = capacity;
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new_items[i] = (struct acolorhist_arr_item){
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.color = px,
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.perceptual_weight = boost,
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};
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achl->used++;
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} else {
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// these are elses for first checks whether first and second inline-stored colors are used
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achl->inline2.color.l = px.l;
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achl->inline2.perceptual_weight = boost;
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achl->used = 2;
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++acht->colors;
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}
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} else {
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achl->inline1.color.l = px.l;
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achl->inline1.perceptual_weight = boost;
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achl->used = 1;
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++acht->colors;
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}
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return true;
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}
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LIQ_PRIVATE struct acolorhash_table *pam_allocacolorhash(unsigned int maxcolors, unsigned int surface, unsigned int ignorebits, void* (*malloc)(size_t), void (*free)(void*))
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{
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const size_t estimated_colors = MIN(maxcolors, surface/(ignorebits + (surface > 512*512 ? 6 : 5)));
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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);
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const size_t mempool_size = sizeof(struct acolorhash_table) + buckets_size + estimated_colors * sizeof(struct acolorhist_arr_item);
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struct acolorhash_table *t = mempool_create(&m, sizeof(*t) + buckets_size, mempool_size, malloc, free);
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if (!t) return NULL;
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*t = (struct acolorhash_table){
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.mempool = m,
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.hash_size = hash_size,
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.maxcolors = maxcolors,
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.ignorebits = ignorebits,
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};
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memset(t->buckets, 0, buckets_size);
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return t;
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}
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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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{
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if (entry->perceptual_weight == 0) {
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return 0;
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}
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const float w = MIN(entry->perceptual_weight/128.f, max_perceptual_weight);
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achv[*j].adjusted_weight = achv[*j].perceptual_weight = w;
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achv[*j].acolor = rgba_to_f(gamma_lut, entry->color.rgba);
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*j += 1;
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return w;
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}
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LIQ_PRIVATE histogram *pam_acolorhashtoacolorhist(const struct acolorhash_table *acht, const double gamma, void* (*malloc)(size_t), void (*free)(void*))
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{
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histogram *hist = malloc(sizeof(hist[0]));
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if (!hist || !acht) return NULL;
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*hist = (histogram){
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.achv = malloc(MAX(1,acht->colors) * sizeof(hist->achv[0])),
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.size = acht->colors,
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.free = free,
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.ignorebits = acht->ignorebits,
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};
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if (!hist->achv) return NULL;
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float gamma_lut[256];
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to_f_set_gamma(gamma_lut, gamma);
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/* Limit perceptual weight to 1/10th of the image surface area to prevent
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a single color from dominating all others. */
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float max_perceptual_weight = 0.1f * acht->cols * acht->rows;
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double total_weight = 0;
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unsigned int j=0;
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for(unsigned int i=0; i < acht->hash_size; ++i) {
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const struct acolorhist_arr_head *const achl = &acht->buckets[i];
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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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}
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}
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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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if (!j) {
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pam_freeacolorhist(hist);
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return NULL;
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}
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return hist;
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}
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LIQ_PRIVATE void pam_freeacolorhash(struct acolorhash_table *acht)
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{
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if (acht) {
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mempool_destroy(acht->mempool);
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}
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}
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LIQ_PRIVATE void pam_freeacolorhist(histogram *hist)
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{
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hist->free(hist->achv);
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hist->free(hist);
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}
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LIQ_PRIVATE colormap *pam_colormap(unsigned int colors, void* (*malloc)(size_t), void (*free)(void*))
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{
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assert(colors > 0 && colors < 65536);
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colormap *map;
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const size_t colors_size = colors * sizeof(map->palette[0]);
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map = malloc(sizeof(colormap) + colors_size);
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if (!map) return NULL;
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*map = (colormap){
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.malloc = malloc,
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.free = free,
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.colors = colors,
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};
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memset(map->palette, 0, colors_size);
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return map;
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}
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LIQ_PRIVATE colormap *pam_duplicate_colormap(colormap *map)
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{
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colormap *dupe = pam_colormap(map->colors, map->malloc, map->free);
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for(unsigned int i=0; i < map->colors; i++) {
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dupe->palette[i] = map->palette[i];
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}
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return dupe;
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}
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LIQ_PRIVATE void pam_freecolormap(colormap *c)
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{
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c->free(c);
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}
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LIQ_PRIVATE void to_f_set_gamma(float gamma_lut[], const double gamma)
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{
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for(int i=0; i < 256; i++) {
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gamma_lut[i] = pow((double)i/255.0, internal_gamma/gamma);
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}
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}
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