279 lines
11 KiB
C
279 lines
11 KiB
C
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/* pam.c - pam (portable alpha map) utility library
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**
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** Copyright (C) 1989, 1991 by Jef Poskanzer.
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** Copyright (C) 1997, 2000, 2002 by Greg Roelofs; based on an idea by
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** Stefan Schneider.
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** © 2009-2013 by Kornel Lesinski.
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**
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** Permission to use, copy, modify, and distribute this software and its
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** documentation for any purpose and without fee is hereby granted, provided
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** that the above copyright notice appear in all copies and that both that
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** copyright notice and this permission notice appear in supporting
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** documentation. This software is provided "as is" without express or
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** implied warranty.
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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 maxacolors = acht->maxcolors, 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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struct acolorhist_arr_head *const buckets = acht->buckets;
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unsigned int colors = acht->colors;
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const unsigned int hash_size = acht->hash_size;
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const unsigned int stacksize = sizeof(acht->freestack)/sizeof(acht->freestack[0]);
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struct acolorhist_arr_item **freestack = acht->freestack;
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unsigned int freestackp=acht->freestackp;
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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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float boost=1.0;
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for(unsigned int col = 0; col < cols; ++col) {
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if (importance_map) {
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boost = 0.5f+ (double)*importance_map++/255.f;
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}
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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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} 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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}
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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 = &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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continue;
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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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continue;
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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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goto continue_outer_loop;
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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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++colors;
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continue;
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}
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if (++colors > maxacolors) {
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acht->colors = colors;
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acht->freestackp = freestackp;
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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 (freestackp <= 0) {
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// estimate how many colors are going to be + headroom
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const int mempool_size = ((acht->rows + rows-row) * 2 * 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 = freestack[--freestackp];
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}
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} else {
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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 (freestackp < stacksize-1) {
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freestack[freestackp++] = other_items;
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}
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const int mempool_size = ((acht->rows + rows-row) * 2 * 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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++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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++colors;
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}
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continue_outer_loop:;
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}
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}
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acht->colors = colors;
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acht->cols = cols;
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acht->rows += rows;
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acht->freestackp = freestackp;
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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 unsigned int estimated_colors = MIN(maxcolors, surface/(ignorebits + (surface > 512*512 ? 5 : 4)));
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const unsigned int hash_size = estimated_colors < 66000 ? 6673 : (estimated_colors < 200000 ? 12011 : 24019);
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mempool m = NULL;
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const unsigned int buckets_size = hash_size * sizeof(struct acolorhist_arr_head);
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const unsigned int 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, hash_size * sizeof(struct acolorhist_arr_head));
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return t;
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}
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#define PAM_ADD_TO_HIST(entry) { \
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hist->achv[j].acolor = to_f(gamma_lut, entry.color.rgba); \
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total_weight += hist->achv[j].adjusted_weight = hist->achv[j].perceptual_weight = MIN(entry.perceptual_weight, max_perceptual_weight); \
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++j; \
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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(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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for(unsigned int j=0, 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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PAM_ADD_TO_HIST(achl->inline1);
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if (achl->used > 1) {
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PAM_ADD_TO_HIST(achl->inline2);
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for(unsigned int k=0; k < achl->used-2; k++) {
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PAM_ADD_TO_HIST(achl->other_items[k]);
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}
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}
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}
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}
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hist->total_perceptual_weight = total_weight;
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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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mempool_destroy(acht->mempool);
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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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.subset_palette = NULL,
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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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if (map->subset_palette) {
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dupe->subset_palette = pam_duplicate_colormap(map->subset_palette);
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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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if (c->subset_palette) pam_freecolormap(c->subset_palette);
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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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