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gstreamer/subprojects/gst-plugins-bad/gst/dvbsubenc/libimagequant/libimagequant.c

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/* pngquant.c - quantize the colors in an alphamap down to a specified number
**
** Copyright (C) 1989, 1991 by Jef Poskanzer.
** Copyright (C) 1997, 2000, 2002 by Greg Roelofs; based on an idea by
** Stefan Schneider.
** © 2009-2013 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 <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stdint.h>
#include <limits.h>
#if !(defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199900L) && !(defined(_MSC_VER) && _MSC_VER >= 1800)
#error "This program requires C99, e.g. -std=c99 switch in GCC or it requires MSVC 18.0 or higher."
#error "Ignore torrent of syntax errors that may follow. It's only because compiler is set to use too old C version."
#endif
#ifdef _OPENMP
#include <omp.h>
#else
#define omp_get_max_threads() 1
#define omp_get_thread_num() 0
#endif
#include "libimagequant.h"
#include "pam.h"
#include "mediancut.h"
#include "nearest.h"
#include "blur.h"
#include "viter.h"
#define LIQ_HIGH_MEMORY_LIMIT (1<<26) /* avoid allocating buffers larger than 64MB */
// each structure has a pointer as a unique identifier that allows type checking at run time
static const char *const liq_attr_magic = "liq_attr", *const liq_image_magic =
"liq_image", *const liq_result_magic =
"liq_result", *const liq_remapping_result_magic =
"liq_remapping_result", *const liq_freed_magic = "free";
#define CHECK_STRUCT_TYPE(attr, kind) liq_crash_if_invalid_handle_pointer_given((const liq_attr*)attr, kind ## _magic)
#define CHECK_USER_POINTER(ptr) liq_crash_if_invalid_pointer_given(ptr)
struct liq_attr
{
const char *magic_header;
void *(*malloc) (size_t);
void (*free) (void *);
double target_mse, max_mse, voronoi_iteration_limit;
float min_opaque_val;
unsigned int max_colors, max_histogram_entries;
unsigned int min_posterization_output /* user setting */ ,
min_posterization_input /* speed setting */ ;
unsigned int voronoi_iterations, feedback_loop_trials;
bool last_index_transparent, use_contrast_maps, use_dither_map, fast_palette;
unsigned int speed;
liq_log_callback_function *log_callback;
void *log_callback_user_info;
liq_log_flush_callback_function *log_flush_callback;
void *log_flush_callback_user_info;
};
struct liq_image
{
const char *magic_header;
void *(*malloc) (size_t);
void (*free) (void *);
f_pixel *f_pixels;
rgba_pixel **rows;
double gamma;
unsigned int width, height;
unsigned char *noise, *edges, *dither_map;
rgba_pixel *pixels, *temp_row;
f_pixel *temp_f_row;
liq_image_get_rgba_row_callback *row_callback;
void *row_callback_user_info;
float min_opaque_val;
f_pixel fixed_colors[256];
unsigned short fixed_colors_count;
bool free_pixels, free_rows, free_rows_internal;
};
typedef struct liq_remapping_result
{
const char *magic_header;
void *(*malloc) (size_t);
void (*free) (void *);
unsigned char *pixels;
colormap *palette;
liq_palette int_palette;
double gamma, palette_error;
float dither_level;
bool use_dither_map;
} liq_remapping_result;
struct liq_result
{
const char *magic_header;
void *(*malloc) (size_t);
void (*free) (void *);
liq_remapping_result *remapping;
colormap *palette;
liq_palette int_palette;
float dither_level;
double gamma, palette_error;
int min_posterization_output;
bool use_dither_map, fast_palette;
};
static liq_result *pngquant_quantize (histogram * hist,
const liq_attr * options, const liq_image * img);
static void modify_alpha (liq_image * input_image,
rgba_pixel * const row_pixels);
static void contrast_maps (liq_image * image);
static histogram *get_histogram (liq_image * input_image,
const liq_attr * options);
static const rgba_pixel *liq_image_get_row_rgba (liq_image * input_image,
unsigned int row);
static const f_pixel *liq_image_get_row_f (liq_image * input_image,
unsigned int row);
static void liq_remapping_result_destroy (liq_remapping_result * result);
static void
liq_verbose_printf (const liq_attr * context, const char *fmt, ...)
{
if (context->log_callback) {
va_list va;
int required_space;
char *buf;
va_start (va, fmt);
required_space = vsnprintf (NULL, 0, fmt, va) + 1; // +\0
va_end (va);
buf = g_alloca (required_space);
va_start (va, fmt);
vsnprintf (buf, required_space, fmt, va);
va_end (va);
context->log_callback (context, buf, context->log_callback_user_info);
}
}
inline static void
verbose_print (const liq_attr * attr, const char *msg)
{
if (attr->log_callback) {
attr->log_callback (attr, msg, attr->log_callback_user_info);
}
}
static void
liq_verbose_printf_flush (liq_attr * attr)
{
if (attr->log_flush_callback) {
attr->log_flush_callback (attr, attr->log_flush_callback_user_info);
}
}
#if USE_SSE
inline static bool
is_sse_available (void)
{
#if (defined(__x86_64__) || defined(__amd64))
return true;
#else
int a, b, c, d;
cpuid (1, a, b, c, d);
return d & (1 << 25); // edx bit 25 is set when SSE is present
#endif
}
#endif
/* make it clear in backtrace when user-supplied handle points to invalid memory */
NEVER_INLINE LIQ_EXPORT bool liq_crash_if_invalid_handle_pointer_given (const
liq_attr * user_supplied_pointer, const char *const expected_magic_header);
LIQ_EXPORT bool
liq_crash_if_invalid_handle_pointer_given (const liq_attr *
user_supplied_pointer, const char *const expected_magic_header)
{
if (!user_supplied_pointer) {
return false;
}
if (user_supplied_pointer->magic_header == liq_freed_magic) {
fprintf (stderr, "%s used after being freed", expected_magic_header);
// this is not normal error handling, this is programmer error that should crash the program.
// program cannot safely continue if memory has been used after it's been freed.
// abort() is nasty, but security vulnerability may be worse.
abort ();
}
return user_supplied_pointer->magic_header == expected_magic_header;
}
NEVER_INLINE LIQ_EXPORT bool liq_crash_if_invalid_pointer_given (void *pointer);
LIQ_EXPORT bool
liq_crash_if_invalid_pointer_given (void *pointer)
{
char test_access;
if (!pointer) {
return false;
}
// Force a read from the given (potentially invalid) memory location in order to check early whether this crashes the program or not.
// It doesn't matter what value is read, the code here is just to shut the compiler up about unused read.
test_access = *((volatile char *) pointer);
return test_access || true;
}
static void
liq_log_error (const liq_attr * attr, const char *msg)
{
if (!CHECK_STRUCT_TYPE (attr, liq_attr))
return;
liq_verbose_printf (attr, " error: %s", msg);
}
static double
quality_to_mse (long quality)
{
const double extra_low_quality_fudge =
MAX (0, 0.016 / (0.001 + quality) - 0.001);
if (quality == 0) {
return MAX_DIFF;
}
if (quality == 100) {
return 0;
}
// curve fudged to be roughly similar to quality of libjpeg
// except lowest 10 for really low number of colors
return extra_low_quality_fudge + 2.5 / pow (210.0 + quality,
1.2) * (100.1 - quality) / 100.0;
}
static unsigned int
mse_to_quality (double mse)
{
int i;
for (i = 100; i > 0; i--) {
if (mse <= quality_to_mse (i) + 0.000001) { // + epsilon for floating point errors
return i;
}
}
return 0;
}
LIQ_EXPORT liq_error
liq_set_quality (liq_attr * attr, int minimum, int target)
{
if (!CHECK_STRUCT_TYPE (attr, liq_attr))
return LIQ_INVALID_POINTER;
if (target < 0 || target > 100 || target < minimum || minimum < 0)
return LIQ_VALUE_OUT_OF_RANGE;
attr->target_mse = quality_to_mse (target);
attr->max_mse = quality_to_mse (minimum);
return LIQ_OK;
}
LIQ_EXPORT int
liq_get_min_quality (const liq_attr * attr)
{
if (!CHECK_STRUCT_TYPE (attr, liq_attr))
return -1;
return mse_to_quality (attr->max_mse);
}
LIQ_EXPORT int
liq_get_max_quality (const liq_attr * attr)
{
if (!CHECK_STRUCT_TYPE (attr, liq_attr))
return -1;
return mse_to_quality (attr->target_mse);
}
LIQ_EXPORT liq_error
liq_set_max_colors (liq_attr * attr, int colors)
{
if (!CHECK_STRUCT_TYPE (attr, liq_attr))
return LIQ_INVALID_POINTER;
if (colors < 2 || colors > 256)
return LIQ_VALUE_OUT_OF_RANGE;
attr->max_colors = colors;
return LIQ_OK;
}
LIQ_EXPORT int
liq_get_max_colors (const liq_attr * attr)
{
if (!CHECK_STRUCT_TYPE (attr, liq_attr))
return -1;
return attr->max_colors;
}
LIQ_EXPORT liq_error
liq_set_min_posterization (liq_attr * attr, int bits)
{
if (!CHECK_STRUCT_TYPE (attr, liq_attr))
return LIQ_INVALID_POINTER;
if (bits < 0 || bits > 4)
return LIQ_VALUE_OUT_OF_RANGE;
attr->min_posterization_output = bits;
return LIQ_OK;
}
LIQ_EXPORT int
liq_get_min_posterization (const liq_attr * attr)
{
if (!CHECK_STRUCT_TYPE (attr, liq_attr))
return -1;
return attr->min_posterization_output;
}
LIQ_EXPORT liq_error
liq_set_speed (liq_attr * attr, int speed)
{
int iterations;
if (!CHECK_STRUCT_TYPE (attr, liq_attr))
return LIQ_INVALID_POINTER;
if (speed < 1 || speed > 10)
return LIQ_VALUE_OUT_OF_RANGE;
iterations = MAX (8 - speed, 0);
iterations += iterations * iterations / 2;
attr->voronoi_iterations = iterations;
attr->voronoi_iteration_limit = 1.0 / (double) (1 << (23 - speed));
attr->feedback_loop_trials = MAX (56 - 9 * speed, 0);
attr->max_histogram_entries = (1 << 17) + (1 << 18) * (10 - speed);
attr->min_posterization_input = (speed >= 8) ? 1 : 0;
attr->fast_palette = (speed >= 7);
attr->use_dither_map = (speed <= (omp_get_max_threads () > 1 ? 7 : 5)); // parallelized dither map might speed up floyd remapping
attr->use_contrast_maps = (speed <= 7) || attr->use_dither_map;
attr->speed = speed;
return LIQ_OK;
}
LIQ_EXPORT int
liq_get_speed (const liq_attr * attr)
{
if (!CHECK_STRUCT_TYPE (attr, liq_attr))
return -1;
return attr->speed;
}
LIQ_EXPORT liq_error
liq_set_output_gamma (liq_result * res, double gamma)
{
if (!CHECK_STRUCT_TYPE (res, liq_result))
return LIQ_INVALID_POINTER;
if (gamma <= 0 || gamma >= 1.0)
return LIQ_VALUE_OUT_OF_RANGE;
if (res->remapping) {
liq_remapping_result_destroy (res->remapping);
res->remapping = NULL;
}
res->gamma = gamma;
return LIQ_OK;
}
LIQ_EXPORT liq_error
liq_set_min_opacity (liq_attr * attr, int min)
{
if (!CHECK_STRUCT_TYPE (attr, liq_attr))
return LIQ_INVALID_POINTER;
if (min < 0 || min > 255)
return LIQ_VALUE_OUT_OF_RANGE;
attr->min_opaque_val = (double) min / 255.0;
return LIQ_OK;
}
LIQ_EXPORT int
liq_get_min_opacity (const liq_attr * attr)
{
if (!CHECK_STRUCT_TYPE (attr, liq_attr))
return -1;
return MIN (255, 256.0 * attr->min_opaque_val);
}
LIQ_EXPORT void
liq_set_last_index_transparent (liq_attr * attr, int is_last)
{
if (!CHECK_STRUCT_TYPE (attr, liq_attr))
return;
attr->last_index_transparent = ! !is_last;
}
LIQ_EXPORT void
liq_set_log_callback (liq_attr * attr, liq_log_callback_function * callback,
void *user_info)
{
if (!CHECK_STRUCT_TYPE (attr, liq_attr))
return;
liq_verbose_printf_flush (attr);
attr->log_callback = callback;
attr->log_callback_user_info = user_info;
}
LIQ_EXPORT void
liq_set_log_flush_callback (liq_attr * attr,
liq_log_flush_callback_function * callback, void *user_info)
{
if (!CHECK_STRUCT_TYPE (attr, liq_attr))
return;
attr->log_flush_callback = callback;
attr->log_flush_callback_user_info = user_info;
}
LIQ_EXPORT liq_attr *
liq_attr_create (void)
{
return liq_attr_create_with_allocator (NULL, NULL);
}
LIQ_EXPORT void
liq_attr_destroy (liq_attr * attr)
{
if (!CHECK_STRUCT_TYPE (attr, liq_attr)) {
return;
}
liq_verbose_printf_flush (attr);
attr->magic_header = liq_freed_magic;
attr->free (attr);
}
LIQ_EXPORT liq_attr *
liq_attr_copy (liq_attr * orig)
{
liq_attr *attr;
if (!CHECK_STRUCT_TYPE (orig, liq_attr)) {
return NULL;
}
attr = orig->malloc (sizeof (liq_attr));
if (!attr)
return NULL;
*attr = *orig;
return attr;
}
static void *
liq_aligned_malloc (size_t size)
{
unsigned char *ptr = malloc (size + 16);
uintptr_t offset;
if (!ptr) {
return NULL;
}
offset = 16 - ((uintptr_t) ptr & 15); // also reserves 1 byte for ptr[-1]
ptr += offset;
assert (0 == (((uintptr_t) ptr) & 15));
ptr[-1] = offset ^ 0x59; // store how much pointer was shifted to get the original for free()
return ptr;
}
static void
liq_aligned_free (void *inptr)
{
unsigned char *ptr = inptr;
size_t offset = ptr[-1] ^ 0x59;
assert (offset > 0 && offset <= 16);
free (ptr - offset);
}
LIQ_EXPORT liq_attr *
liq_attr_create_with_allocator (void *(*custom_malloc) (size_t),
void (*custom_free) (void *))
{
liq_attr *attr;
#if USE_SSE
if (!is_sse_available ()) {
return NULL;
}
#endif
if (!custom_malloc && !custom_free) {
custom_malloc = liq_aligned_malloc;
custom_free = liq_aligned_free;
} else if (!custom_malloc != !custom_free) {
return NULL; // either specify both or none
}
attr = custom_malloc (sizeof (liq_attr));
if (!attr)
return NULL;
*attr = (liq_attr) {
.magic_header = liq_attr_magic,.malloc = custom_malloc,.free = custom_free,.max_colors = 256,.min_opaque_val = 1, // whether preserve opaque colors for IE (1.0=no, does not affect alpha)
.last_index_transparent = false, // puts transparent color at last index. This is workaround for blu-ray subtitles.
.target_mse = 0,.max_mse = MAX_DIFF,};
liq_set_speed (attr, 3);
return attr;
}
LIQ_EXPORT liq_error
liq_image_add_fixed_color (liq_image * img, liq_color color)
{
float gamma_lut[256];
rgba_pixel pix = (rgba_pixel) {
.r = color.r,
.g = color.g,
.b = color.b,
.a = color.a
};
if (!CHECK_STRUCT_TYPE (img, liq_image))
return LIQ_INVALID_POINTER;
if (img->fixed_colors_count > 255)
return LIQ_BUFFER_TOO_SMALL;
to_f_set_gamma (gamma_lut, img->gamma);
img->fixed_colors[img->fixed_colors_count++] = to_f (gamma_lut, pix);
return LIQ_OK;
}
static bool
liq_image_use_low_memory (liq_image * img)
{
img->temp_f_row =
img->malloc (sizeof (img->f_pixels[0]) * img->width *
omp_get_max_threads ());
return img->temp_f_row != NULL;
}
static bool
liq_image_should_use_low_memory (liq_image * img, const bool low_memory_hint)
{
return img->width * img->height > (low_memory_hint ? LIQ_HIGH_MEMORY_LIMIT / 8 : LIQ_HIGH_MEMORY_LIMIT) / sizeof (f_pixel); // Watch out for integer overflow
}
static liq_image *
liq_image_create_internal (liq_attr * attr, rgba_pixel * rows[],
liq_image_get_rgba_row_callback * row_callback,
void *row_callback_user_info, int width, int height, double gamma)
{
liq_image *img;
if (gamma < 0 || gamma > 1.0) {
liq_log_error (attr, "gamma must be >= 0 and <= 1 (try 1/gamma instead)");
return NULL;
}
if (!rows && !row_callback) {
liq_log_error (attr, "missing row data");
return NULL;
}
img = attr->malloc (sizeof (liq_image));
if (!img)
return NULL;
*img = (liq_image) {
.magic_header = liq_image_magic,.malloc = attr->malloc,.free =
attr->free,.width = width,.height = height,.gamma =
gamma ? gamma : 0.45455,.rows = rows,.row_callback =
row_callback,.row_callback_user_info =
row_callback_user_info,.min_opaque_val = attr->min_opaque_val,};
if (!rows || attr->min_opaque_val < 1.f) {
img->temp_row =
attr->malloc (sizeof (img->temp_row[0]) * width *
omp_get_max_threads ());
if (!img->temp_row)
return NULL;
}
// if image is huge or converted pixels are not likely to be reused then don't cache converted pixels
if (liq_image_should_use_low_memory (img, !img->temp_row
&& !attr->use_contrast_maps && !attr->use_dither_map)) {
verbose_print (attr, " conserving memory");
if (!liq_image_use_low_memory (img))
return NULL;
}
if (img->min_opaque_val < 1.f) {
verbose_print (attr,
" Working around IE6 bug by making image less transparent...");
}
return img;
}
LIQ_EXPORT liq_error
liq_image_set_memory_ownership (liq_image * img, int ownership_flags)
{
if (!CHECK_STRUCT_TYPE (img, liq_image))
return LIQ_INVALID_POINTER;
if (!img->rows || !ownership_flags
|| (ownership_flags & ~(LIQ_OWN_ROWS | LIQ_OWN_PIXELS))) {
return LIQ_VALUE_OUT_OF_RANGE;
}
if (ownership_flags & LIQ_OWN_ROWS) {
if (img->free_rows_internal)
return LIQ_VALUE_OUT_OF_RANGE;
img->free_rows = true;
}
if (ownership_flags & LIQ_OWN_PIXELS) {
img->free_pixels = true;
if (!img->pixels) {
// for simplicity of this API there's no explicit bitmap argument,
// so the row with the lowest address is assumed to be at the start of the bitmap
img->pixels = img->rows[0];
for (unsigned int i = 1; i < img->height; i++) {
img->pixels = MIN (img->pixels, img->rows[i]);
}
}
}
return LIQ_OK;
}
static bool
check_image_size (const liq_attr * attr, const int width, const int height)
{
if (!CHECK_STRUCT_TYPE (attr, liq_attr)) {
return false;
}
if (width <= 0 || height <= 0) {
liq_log_error (attr, "width and height must be > 0");
return false;
}
if (width > INT_MAX / height) {
liq_log_error (attr, "image too large");
return false;
}
return true;
}
LIQ_EXPORT liq_image *
liq_image_create_custom (liq_attr * attr,
liq_image_get_rgba_row_callback * row_callback, void *user_info, int width,
int height, double gamma)
{
if (!check_image_size (attr, width, height)) {
return NULL;
}
return liq_image_create_internal (attr, NULL, row_callback, user_info, width,
height, gamma);
}
LIQ_EXPORT liq_image *
liq_image_create_rgba_rows (liq_attr * attr, void *rows[], int width,
int height, double gamma)
{
if (!check_image_size (attr, width, height)) {
return NULL;
}
for (int i = 0; i < height; i++) {
if (!CHECK_USER_POINTER (rows + i) || !CHECK_USER_POINTER (rows[i])) {
liq_log_error (attr, "invalid row pointers");
return NULL;
}
}
return liq_image_create_internal (attr, (rgba_pixel **) rows, NULL, NULL,
width, height, gamma);
}
LIQ_EXPORT liq_image *
liq_image_create_rgba (liq_attr * attr, void *bitmap, int width, int height,
double gamma)
{
rgba_pixel *pixels;
rgba_pixel **rows;
liq_image *image;
if (!check_image_size (attr, width, height)) {
return NULL;
}
if (!CHECK_USER_POINTER (bitmap)) {
liq_log_error (attr, "invalid bitmap pointer");
return NULL;
}
pixels = bitmap;
rows = attr->malloc (sizeof (rows[0]) * height);
if (!rows)
return NULL;
for (int i = 0; i < height; i++) {
rows[i] = pixels + width * i;
}
image =
liq_image_create_internal (attr, rows, NULL, NULL, width, height, gamma);
image->free_rows = true;
image->free_rows_internal = true;
return image;
}
NEVER_INLINE LIQ_EXPORT void
liq_executing_user_callback (liq_image_get_rgba_row_callback * callback,
liq_color * temp_row, int row, int width, void *user_info);
LIQ_EXPORT void
liq_executing_user_callback (liq_image_get_rgba_row_callback * callback,
liq_color * temp_row, int row, int width, void *user_info)
{
assert (callback);
assert (temp_row);
callback (temp_row, row, width, user_info);
}
inline static bool
liq_image_can_use_rows (liq_image * img)
{
const bool iebug = img->min_opaque_val < 1.f;
return (img->rows && !iebug);
}
static const rgba_pixel *
liq_image_get_row_rgba (liq_image * img, unsigned int row)
{
rgba_pixel *temp_row;
if (liq_image_can_use_rows (img)) {
return img->rows[row];
}
assert (img->temp_row);
temp_row = img->temp_row + img->width * omp_get_thread_num ();
if (img->rows) {
memcpy (temp_row, img->rows[row], img->width * sizeof (temp_row[0]));
} else {
liq_executing_user_callback (img->row_callback, (liq_color *) temp_row, row,
img->width, img->row_callback_user_info);
}
if (img->min_opaque_val < 1.f)
modify_alpha (img, temp_row);
return temp_row;
}
static void
convert_row_to_f (liq_image * img, f_pixel * row_f_pixels,
const unsigned int row, const float gamma_lut[])
{
assert (row_f_pixels);
assert (!USE_SSE || 0 == ((uintptr_t) row_f_pixels & 15));
{
const rgba_pixel *const row_pixels = liq_image_get_row_rgba (img, row);
unsigned int col;
for (col = 0; col < img->width; col++) {
row_f_pixels[col] = to_f (gamma_lut, row_pixels[col]);
}
}
}
static const f_pixel *
liq_image_get_row_f (liq_image * img, unsigned int row)
{
if (!img->f_pixels) {
if (img->temp_f_row) {
float gamma_lut[256];
f_pixel *row_for_thread;
to_f_set_gamma (gamma_lut, img->gamma);
row_for_thread = img->temp_f_row + img->width * omp_get_thread_num ();
convert_row_to_f (img, row_for_thread, row, gamma_lut);
return row_for_thread;
}
assert (omp_get_thread_num () == 0);
if (!liq_image_should_use_low_memory (img, false)) {
img->f_pixels =
img->malloc (sizeof (img->f_pixels[0]) * img->width * img->height);
}
if (!img->f_pixels) {
if (!liq_image_use_low_memory (img))
return NULL;
return liq_image_get_row_f (img, row);
}
{
float gamma_lut[256];
to_f_set_gamma (gamma_lut, img->gamma);
for (unsigned int i = 0; i < img->height; i++) {
convert_row_to_f (img, &img->f_pixels[i * img->width], i, gamma_lut);
}
}
}
return img->f_pixels + img->width * row;
}
LIQ_EXPORT int
liq_image_get_width (const liq_image * input_image)
{
if (!CHECK_STRUCT_TYPE (input_image, liq_image))
return -1;
return input_image->width;
}
LIQ_EXPORT int
liq_image_get_height (const liq_image * input_image)
{
if (!CHECK_STRUCT_TYPE (input_image, liq_image))
return -1;
return input_image->height;
}
typedef void free_func (void *);
static free_func *
get_default_free_func (liq_image * img)
{
// When default allocator is used then user-supplied pointers must be freed with free()
if (img->free_rows_internal || img->free != liq_aligned_free) {
return img->free;
}
return free;
}
static void
liq_image_free_rgba_source (liq_image * input_image)
{
if (input_image->free_pixels && input_image->pixels) {
get_default_free_func (input_image) (input_image->pixels);
input_image->pixels = NULL;
}
if (input_image->free_rows && input_image->rows) {
get_default_free_func (input_image) (input_image->rows);
input_image->rows = NULL;
}
}
LIQ_EXPORT void
liq_image_destroy (liq_image * input_image)
{
if (!CHECK_STRUCT_TYPE (input_image, liq_image))
return;
liq_image_free_rgba_source (input_image);
if (input_image->noise) {
input_image->free (input_image->noise);
}
if (input_image->edges) {
input_image->free (input_image->edges);
}
if (input_image->dither_map) {
input_image->free (input_image->dither_map);
}
if (input_image->f_pixels) {
input_image->free (input_image->f_pixels);
}
if (input_image->temp_row) {
input_image->free (input_image->temp_row);
}
if (input_image->temp_f_row) {
input_image->free (input_image->temp_f_row);
}
input_image->magic_header = liq_freed_magic;
input_image->free (input_image);
}
LIQ_EXPORT liq_result *
liq_quantize_image (liq_attr * attr, liq_image * img)
{
histogram *hist;
liq_result *result;
if (!CHECK_STRUCT_TYPE (attr, liq_attr))
return NULL;
if (!CHECK_STRUCT_TYPE (img, liq_image)) {
liq_log_error (attr, "invalid image pointer");
return NULL;
}
hist = get_histogram (img, attr);
if (!hist) {
return NULL;
}
result = pngquant_quantize (hist, attr, img);
pam_freeacolorhist (hist);
return result;
}
LIQ_EXPORT liq_error
liq_set_dithering_level (liq_result * res, float dither_level)
{
if (!CHECK_STRUCT_TYPE (res, liq_result))
return LIQ_INVALID_POINTER;
if (res->remapping) {
liq_remapping_result_destroy (res->remapping);
res->remapping = NULL;
}
if (res->dither_level < 0 || res->dither_level > 1.0f)
return LIQ_VALUE_OUT_OF_RANGE;
res->dither_level = dither_level;
return LIQ_OK;
}
static liq_remapping_result *
liq_remapping_result_create (liq_result * result)
{
liq_remapping_result *res;
if (!CHECK_STRUCT_TYPE (result, liq_result)) {
return NULL;
}
res = result->malloc (sizeof (liq_remapping_result));
if (!res)
return NULL;
*res = (liq_remapping_result) {
.magic_header = liq_remapping_result_magic,.malloc = result->malloc,.free =
result->free,.dither_level = result->dither_level,.use_dither_map =
result->use_dither_map,.palette_error = result->palette_error,.gamma =
result->gamma,.palette = pam_duplicate_colormap (result->palette),};
return res;
}
LIQ_EXPORT double
liq_get_output_gamma (const liq_result * result)
{
if (!CHECK_STRUCT_TYPE (result, liq_result))
return -1;
return result->gamma;
}
static void
liq_remapping_result_destroy (liq_remapping_result * result)
{
if (!CHECK_STRUCT_TYPE (result, liq_remapping_result))
return;
if (result->palette)
pam_freecolormap (result->palette);
if (result->pixels)
result->free (result->pixels);
result->magic_header = liq_freed_magic;
result->free (result);
}
LIQ_EXPORT void
liq_result_destroy (liq_result * res)
{
if (!CHECK_STRUCT_TYPE (res, liq_result))
return;
memset (&res->int_palette, 0, sizeof (liq_palette));
if (res->remapping) {
memset (&res->remapping->int_palette, 0, sizeof (liq_palette));
liq_remapping_result_destroy (res->remapping);
}
pam_freecolormap (res->palette);
res->magic_header = liq_freed_magic;
res->free (res);
}
LIQ_EXPORT double
liq_get_quantization_error (liq_result * result)
{
if (!CHECK_STRUCT_TYPE (result, liq_result))
return -1;
if (result->palette_error >= 0) {
return result->palette_error * 65536.0 / 6.0;
}
if (result->remapping && result->remapping->palette_error >= 0) {
return result->remapping->palette_error * 65536.0 / 6.0;
}
return result->palette_error;
}
LIQ_EXPORT int
liq_get_quantization_quality (liq_result * result)
{
if (!CHECK_STRUCT_TYPE (result, liq_result))
return -1;
if (result->palette_error >= 0) {
return mse_to_quality (result->palette_error);
}
if (result->remapping && result->remapping->palette_error >= 0) {
return mse_to_quality (result->remapping->palette_error);
}
return result->palette_error;
}
static int
compare_popularity (const void *ch1, const void *ch2)
{
const float v1 = ((const colormap_item *) ch1)->popularity;
const float v2 = ((const colormap_item *) ch2)->popularity;
return v1 > v2 ? -1 : 1;
}
static void
sort_palette_qsort (colormap * map, int start, int nelem)
{
qsort (map->palette + start, nelem, sizeof (map->palette[0]),
compare_popularity);
}
#define SWAP_PALETTE(map, a,b) { \
const colormap_item tmp = (map)->palette[(a)]; \
(map)->palette[(a)] = (map)->palette[(b)]; \
(map)->palette[(b)] = tmp; }
static void
sort_palette (colormap * map, const liq_attr * options)
{
unsigned int i;
unsigned int num_transparent;
/*
** Step 3.5 [GRR]: remap the palette colors so that all entries with
** the maximal alpha value (i.e., fully opaque) are at the end and can
** therefore be omitted from the tRNS chunk.
*/
if (options->last_index_transparent) {
for (i = 0; i < map->colors; i++) {
if (map->palette[i].acolor.a < 1.0 / 256.0) {
const unsigned int old = i, transparent_dest = map->colors - 1;
SWAP_PALETTE (map, transparent_dest, old);
/* colors sorted by popularity make pngs slightly more compressible */
sort_palette_qsort (map, 0, map->colors - 1);
return;
}
}
}
/* move transparent colors to the beginning to shrink trns chunk */
num_transparent = 0;
for (i = 0; i < map->colors; i++) {
if (map->palette[i].acolor.a < 255.0 / 256.0) {
// current transparent color is swapped with earlier opaque one
if (i != num_transparent) {
SWAP_PALETTE (map, num_transparent, i);
i--;
}
num_transparent++;
}
}
liq_verbose_printf (options,
" eliminated opaque tRNS-chunk entries...%d entr%s transparent",
num_transparent, (num_transparent == 1) ? "y" : "ies");
/* colors sorted by popularity make pngs slightly more compressible
* opaque and transparent are sorted separately
*/
sort_palette_qsort (map, 0, num_transparent);
sort_palette_qsort (map, num_transparent, map->colors - num_transparent);
if (map->colors > 16) {
SWAP_PALETTE (map, 7, 1); // slightly improves compression
SWAP_PALETTE (map, 8, 2);
SWAP_PALETTE (map, 9, 3);
}
}
inline static unsigned int
posterize_channel (unsigned int color, unsigned int bits)
{
return (color & ~((1 << bits) - 1)) | (color >> (8 - bits));
}
static void
set_rounded_palette (liq_palette * const dest, colormap * const map,
const double gamma, unsigned int posterize)
{
float gamma_lut[256];
to_f_set_gamma (gamma_lut, gamma);
dest->count = map->colors;
for (unsigned int x = 0; x < map->colors; ++x) {
rgba_pixel px = to_rgb (gamma, map->palette[x].acolor);
px.r = posterize_channel (px.r, posterize);
px.g = posterize_channel (px.g, posterize);
px.b = posterize_channel (px.b, posterize);
px.a = posterize_channel (px.a, posterize);
map->palette[x].acolor = to_f (gamma_lut, px); /* saves rounding error introduced by to_rgb, which makes remapping & dithering more accurate */
if (!px.a) {
px.r = 'L';
px.g = 'i';
px.b = 'q';
}
dest->entries[x] = (liq_color) {
.r = px.r,.g = px.g,.b = px.b,.a = px.a};
}
}
LIQ_EXPORT const liq_palette *
liq_get_palette (liq_result * result)
{
if (!CHECK_STRUCT_TYPE (result, liq_result))
return NULL;
if (result->remapping && result->remapping->int_palette.count) {
return &result->remapping->int_palette;
}
if (!result->int_palette.count) {
set_rounded_palette (&result->int_palette, result->palette, result->gamma,
result->min_posterization_output);
}
return &result->int_palette;
}
#define MAX_THREADS 8
static float
remap_to_palette (liq_image * const input_image,
unsigned char *const *const output_pixels, colormap * const map,
const bool fast)
{
const int rows = input_image->height;
const unsigned int cols = input_image->width;
const float min_opaque_val = input_image->min_opaque_val;
double remapping_error = 0;
if (!liq_image_get_row_f (input_image, 0)) { // trigger lazy conversion
return -1;
}
{
struct nearest_map *const n = nearest_init (map, fast);
const unsigned int max_threads = MIN (MAX_THREADS, omp_get_max_threads ());
viter_state *average_color =
g_alloca (sizeof (viter_state) * (VITER_CACHE_LINE_GAP +
map->colors) * MAX_THREADS);
unsigned int row, col;
viter_init (map, max_threads, average_color);
#pragma omp parallel for if (rows*cols > 3000) \
schedule(static) default(none) shared(average_color) reduction(+:remapping_error)
for (row = 0; row < rows; ++row) {
const f_pixel *const row_pixels = liq_image_get_row_f (input_image, row);
unsigned int last_match = 0;
for (col = 0; col < cols; ++col) {
f_pixel px = row_pixels[col];
float diff;
output_pixels[row][col] = last_match =
nearest_search (n, px, last_match, min_opaque_val, &diff);
remapping_error += diff;
viter_update_color (px, 1.0, map, last_match, omp_get_thread_num (),
average_color);
}
}
viter_finalize (map, max_threads, average_color);
nearest_free (n);
}
return remapping_error / (input_image->width * input_image->height);
}
inline static f_pixel
get_dithered_pixel (const float dither_level, const float max_dither_error,
const f_pixel thiserr, const f_pixel px)
{
/* Use Floyd-Steinberg errors to adjust actual color. */
const float sr = thiserr.r * dither_level,
sg = thiserr.g * dither_level,
sb = thiserr.b * dither_level, sa = thiserr.a * dither_level;
float a;
float ratio = 1.0;
float dither_error;
// allowing some overflow prevents undithered bands caused by clamping of all channels
if (px.r + sr > 1.03)
ratio = MIN (ratio, (1.03 - px.r) / sr);
else if (px.r + sr < 0)
ratio = MIN (ratio, px.r / -sr);
if (px.g + sg > 1.03)
ratio = MIN (ratio, (1.03 - px.g) / sg);
else if (px.g + sg < 0)
ratio = MIN (ratio, px.g / -sg);
if (px.b + sb > 1.03)
ratio = MIN (ratio, (1.03 - px.b) / sb);
else if (px.b + sb < 0)
ratio = MIN (ratio, px.b / -sb);
a = px.a + sa;
if (a > 1.0) {
a = 1.0;
} else if (a < 0) {
a = 0;
}
// If dithering error is crazy high, don't propagate it that much
// This prevents crazy geen pixels popping out of the blue (or red or black! ;)
dither_error = sr * sr + sg * sg + sb * sb + sa * sa;
if (dither_error > max_dither_error) {
ratio *= 0.8;
} else if (dither_error < 2.f / 256.f / 256.f) {
// don't dither areas that don't have noticeable error — makes file smaller
return px;
}
return (f_pixel) {
.r = px.r + sr * ratio,.g = px.g + sg * ratio,.b = px.b + sb * ratio,.a = a,};
}
/**
Uses edge/noise map to apply dithering only to flat areas. Dithering on edges creates jagged lines, and noisy areas are "naturally" dithered.
If output_image_is_remapped is true, only pixels noticeably changed by error diffusion will be written to output image.
*/
static void
remap_to_palette_floyd (liq_image * input_image,
unsigned char *const output_pixels[], const colormap * map,
const float max_dither_error, const bool use_dither_map,
const bool output_image_is_remapped, float base_dithering_level)
{
const unsigned int rows = input_image->height, cols = input_image->width;
const unsigned char *dither_map =
use_dither_map ? (input_image->
dither_map ? input_image->dither_map : input_image->edges) : NULL;
const float min_opaque_val = input_image->min_opaque_val;
const colormap_item *acolormap = map->palette;
struct nearest_map *const n = nearest_init (map, false);
unsigned int col;
/* Initialize Floyd-Steinberg error vectors. */
f_pixel *restrict thiserr, *restrict nexterr;
thiserr = input_image->malloc ((cols + 2) * sizeof (*thiserr) * 2); // +2 saves from checking out of bounds access
nexterr = thiserr + (cols + 2);
srand (12345); /* deterministic dithering is better for comparing results */
if (!thiserr)
return;
for (col = 0; col < cols + 2; ++col) {
const double rand_max = RAND_MAX;
thiserr[col].r = ((double) rand () - rand_max / 2.0) / rand_max / 255.0;
thiserr[col].g = ((double) rand () - rand_max / 2.0) / rand_max / 255.0;
thiserr[col].b = ((double) rand () - rand_max / 2.0) / rand_max / 255.0;
thiserr[col].a = ((double) rand () - rand_max / 2.0) / rand_max / 255.0;
}
// response to this value is non-linear and without it any value < 0.8 would give almost no dithering
base_dithering_level =
1.0 - (1.0 - base_dithering_level) * (1.0 - base_dithering_level) * (1.0 -
base_dithering_level);
if (dither_map) {
base_dithering_level *= 1.0 / 255.0; // convert byte to float
}
base_dithering_level *= 15.0 / 16.0; // prevent small errors from accumulating
{
bool fs_direction = true;
unsigned int last_match = 0;
for (unsigned int row = 0; row < rows; ++row) {
unsigned int col = (fs_direction) ? 0 : (cols - 1);
const f_pixel *const row_pixels = liq_image_get_row_f (input_image, row);
memset (nexterr, 0, (cols + 2) * sizeof (*nexterr));
do {
float dither_level = base_dithering_level;
f_pixel spx, xp, err;
unsigned int guessed_match;
if (dither_map) {
dither_level *= dither_map[row * cols + col];
}
spx =
get_dithered_pixel (dither_level, max_dither_error,
thiserr[col + 1], row_pixels[col]);
guessed_match =
output_image_is_remapped ? output_pixels[row][col] : last_match;
output_pixels[row][col] = last_match =
nearest_search (n, spx, guessed_match, min_opaque_val, NULL);
xp = acolormap[last_match].acolor;
err.r = spx.r - xp.r;
err.g = spx.r - xp.g;
err.b = spx.r - xp.b;
err.a = spx.r - xp.a;
// If dithering error is crazy high, don't propagate it that much
// This prevents crazy geen pixels popping out of the blue (or red or black! ;)
if (err.r * err.r + err.g * err.g + err.b * err.b + err.a * err.a >
max_dither_error) {
dither_level *= 0.75;
}
{
const float colorimp =
(3.0f + acolormap[last_match].acolor.a) / 4.0f * dither_level;
err.r *= colorimp;
err.g *= colorimp;
err.b *= colorimp;
err.a *= dither_level;
}
/* Propagate Floyd-Steinberg error terms. */
if (fs_direction) {
thiserr[col + 2].a += err.a * (7.f / 16.f);
thiserr[col + 2].r += err.r * (7.f / 16.f);
thiserr[col + 2].g += err.g * (7.f / 16.f);
thiserr[col + 2].b += err.b * (7.f / 16.f);
nexterr[col + 2].a = err.a * (1.f / 16.f);
nexterr[col + 2].r = err.r * (1.f / 16.f);
nexterr[col + 2].g = err.g * (1.f / 16.f);
nexterr[col + 2].b = err.b * (1.f / 16.f);
nexterr[col + 1].a += err.a * (5.f / 16.f);
nexterr[col + 1].r += err.r * (5.f / 16.f);
nexterr[col + 1].g += err.g * (5.f / 16.f);
nexterr[col + 1].b += err.b * (5.f / 16.f);
nexterr[col].a += err.a * (3.f / 16.f);
nexterr[col].r += err.r * (3.f / 16.f);
nexterr[col].g += err.g * (3.f / 16.f);
nexterr[col].b += err.b * (3.f / 16.f);
} else {
thiserr[col].a += err.a * (7.f / 16.f);
thiserr[col].r += err.r * (7.f / 16.f);
thiserr[col].g += err.g * (7.f / 16.f);
thiserr[col].b += err.b * (7.f / 16.f);
nexterr[col].a = err.a * (1.f / 16.f);
nexterr[col].r = err.r * (1.f / 16.f);
nexterr[col].g = err.g * (1.f / 16.f);
nexterr[col].b = err.b * (1.f / 16.f);
nexterr[col + 1].a += err.a * (5.f / 16.f);
nexterr[col + 1].r += err.r * (5.f / 16.f);
nexterr[col + 1].g += err.g * (5.f / 16.f);
nexterr[col + 1].b += err.b * (5.f / 16.f);
nexterr[col + 2].a += err.a * (3.f / 16.f);
nexterr[col + 2].r += err.r * (3.f / 16.f);
nexterr[col + 2].g += err.g * (3.f / 16.f);
nexterr[col + 2].b += err.b * (3.f / 16.f);
}
// remapping is done in zig-zag
if (fs_direction) {
++col;
if (col >= cols)
break;
} else {
if (col <= 0)
break;
--col;
}
} while (1);
{
f_pixel *const temperr = thiserr;
thiserr = nexterr;
nexterr = temperr;
}
fs_direction = !fs_direction;
}
}
input_image->free (MIN (thiserr, nexterr)); // MIN because pointers were swapped
nearest_free (n);
}
/* fixed colors are always included in the palette, so it would be wasteful to duplicate them in palette from histogram */
static void
remove_fixed_colors_from_histogram (histogram * hist,
const liq_image * input_image, const float target_mse)
{
const float max_difference = MAX (target_mse / 2.0, 2.0 / 256.0 / 256.0);
if (input_image->fixed_colors_count) {
for (int j = 0; j < hist->size; j++) {
for (unsigned int i = 0; i < input_image->fixed_colors_count; i++) {
if (colordifference (hist->achv[j].acolor,
input_image->fixed_colors[i]) < max_difference) {
hist->achv[j] = hist->achv[--hist->size]; // remove color from histogram by overwriting with the last entry
j--;
break; // continue searching histogram
}
}
}
}
}
/* histogram contains information how many times each color is present in the image, weighted by importance_map */
static histogram *
get_histogram (liq_image * input_image, const liq_attr * options)
{
unsigned int ignorebits =
MAX (options->min_posterization_output, options->min_posterization_input);
const unsigned int cols = input_image->width, rows = input_image->height;
if (!input_image->noise && options->use_contrast_maps) {
contrast_maps (input_image);
}
/*
** Step 2: attempt to make a histogram of the colors, unclustered.
** If at first we don't succeed, increase ignorebits to increase color
** coherence and try again.
*/
{
unsigned int maxcolors = options->max_histogram_entries;
struct acolorhash_table *acht;
const bool all_rows_at_once = liq_image_can_use_rows (input_image);
histogram *hist;
do {
acht =
pam_allocacolorhash (maxcolors, rows * cols, ignorebits,
options->malloc, options->free);
if (!acht)
return NULL;
// histogram uses noise contrast map for importance. Color accuracy in noisy areas is not very important.
// noise map does not include edges to avoid ruining anti-aliasing
for (unsigned int row = 0; row < rows; row++) {
bool added_ok;
if (all_rows_at_once) {
added_ok =
pam_computeacolorhash (acht,
(const rgba_pixel * const *) input_image->rows, cols, rows,
input_image->noise);
if (added_ok)
break;
} else {
const rgba_pixel *rows_p[1] =
{ liq_image_get_row_rgba (input_image, row) };
added_ok =
pam_computeacolorhash (acht, rows_p, cols, 1,
input_image->noise ? &input_image->noise[row * cols] : NULL);
}
if (!added_ok) {
ignorebits++;
liq_verbose_printf (options,
" too many colors! Scaling colors to improve clustering... %d",
ignorebits);
pam_freeacolorhash (acht);
acht = NULL;
break;
}
}
} while (!acht);
if (input_image->noise) {
input_image->free (input_image->noise);
input_image->noise = NULL;
}
if (input_image->free_pixels && input_image->f_pixels) {
liq_image_free_rgba_source (input_image); // bow can free the RGBA source if copy has been made in f_pixels
}
hist =
pam_acolorhashtoacolorhist (acht, input_image->gamma, options->malloc,
options->free);
pam_freeacolorhash (acht);
if (hist) {
liq_verbose_printf (options, " made histogram...%d colors found",
hist->size);
remove_fixed_colors_from_histogram (hist, input_image,
options->target_mse);
}
return hist;
}
}
static void
modify_alpha (liq_image * input_image, rgba_pixel * const row_pixels)
{
/* IE6 makes colors with even slightest transparency completely transparent,
thus to improve situation in IE, make colors that are less than ~10% transparent
completely opaque */
const float min_opaque_val = input_image->min_opaque_val;
const float almost_opaque_val = min_opaque_val * 169.f / 256.f;
const unsigned int almost_opaque_val_int =
(min_opaque_val * 169.f / 256.f) * 255.f;
for (unsigned int col = 0; col < input_image->width; col++) {
const rgba_pixel px = row_pixels[col];
/* ie bug: to avoid visible step caused by forced opaqueness, linearily raise opaqueness of almost-opaque colors */
if (px.a >= almost_opaque_val_int) {
float al = px.a / 255.f;
al = almost_opaque_val + (al - almost_opaque_val) * (1.f -
almost_opaque_val) / (min_opaque_val - almost_opaque_val);
al *= 256.f;
row_pixels[col].a = al >= 255.f ? 255 : al;
}
}
}
/**
Builds two maps:
noise - approximation of areas with high-frequency noise, except straight edges. 1=flat, 0=noisy.
edges - noise map including all edges
*/
static void
contrast_maps (liq_image * image)
{
const int cols = image->width, rows = image->height;
unsigned char *restrict noise, *restrict edges, *restrict tmp;
const f_pixel *curr_row, *prev_row, *next_row;
int i, j;
if (cols < 4 || rows < 4 || (3 * cols * rows) > LIQ_HIGH_MEMORY_LIMIT) {
return;
}
noise = image->malloc (cols * rows);
edges = image->malloc (cols * rows);
tmp = image->malloc (cols * rows);
if (!noise || !edges || !tmp) {
return;
}
curr_row = prev_row = next_row = liq_image_get_row_f (image, 0);
for (j = 0; j < rows; j++) {
f_pixel prev, curr, next;
prev_row = curr_row;
curr_row = next_row;
next_row = liq_image_get_row_f (image, MIN (rows - 1, j + 1));
curr = curr_row[0];
next = curr;
for (i = 0; i < cols; i++) {
prev = curr;
curr = next;
next = curr_row[MIN (cols - 1, i + 1)];
// contrast is difference between pixels neighbouring horizontally and vertically
{
const float a = fabsf (prev.a + next.a - curr.a * 2.f),
r = fabsf (prev.r + next.r - curr.r * 2.f),
g = fabsf (prev.g + next.g - curr.g * 2.f),
b = fabsf (prev.b + next.b - curr.b * 2.f);
const f_pixel prevl = prev_row[i];
const f_pixel nextl = next_row[i];
const float a1 = fabsf (prevl.a + nextl.a - curr.a * 2.f),
r1 = fabsf (prevl.r + nextl.r - curr.r * 2.f),
g1 = fabsf (prevl.g + nextl.g - curr.g * 2.f),
b1 = fabsf (prevl.b + nextl.b - curr.b * 2.f);
const float horiz = MAX (MAX (a, r), MAX (g, b));
const float vert = MAX (MAX (a1, r1), MAX (g1, b1));
const float edge = MAX (horiz, vert);
float z = edge - fabsf (horiz - vert) * .5f;
z = 1.f - MAX (z, MIN (horiz, vert));
z *= z; // noise is amplified
z *= z;
z *= 256.f;
noise[j * cols + i] = z < 256 ? z : 255;
z = (1.f - edge) * 256.f;
edges[j * cols + i] = z < 256 ? z : 255;
}
}
}
// noise areas are shrunk and then expanded to remove thin edges from the map
liq_max3 (noise, tmp, cols, rows);
liq_max3 (tmp, noise, cols, rows);
liq_blur (noise, tmp, noise, cols, rows, 3);
liq_max3 (noise, tmp, cols, rows);
liq_min3 (tmp, noise, cols, rows);
liq_min3 (noise, tmp, cols, rows);
liq_min3 (tmp, noise, cols, rows);
liq_min3 (edges, tmp, cols, rows);
liq_max3 (tmp, edges, cols, rows);
for (int i = 0; i < cols * rows; i++)
edges[i] = MIN (noise[i], edges[i]);
image->free (tmp);
image->noise = noise;
image->edges = edges;
}
/**
* Builds map of neighbor pixels mapped to the same palette entry
*
* For efficiency/simplicity it mainly looks for same consecutive pixels horizontally
* and peeks 1 pixel above/below. Full 2d algorithm doesn't improve it significantly.
* Correct flood fill doesn't have visually good properties.
*/
static void
update_dither_map (unsigned char *const *const row_pointers,
liq_image * input_image)
{
const unsigned int width = input_image->width;
const unsigned int height = input_image->height;
unsigned char *const edges = input_image->edges;
for (unsigned int row = 0; row < height; row++) {
unsigned char lastpixel = row_pointers[row][0];
unsigned int lastcol = 0;
for (unsigned int col = 1; col < width; col++) {
const unsigned char px = row_pointers[row][col];
if (px != lastpixel || col == width - 1) {
float neighbor_count = 2.5f + col - lastcol;
unsigned int i = lastcol;
while (i < col) {
if (row > 0) {
unsigned char pixelabove = row_pointers[row - 1][i];
if (pixelabove == lastpixel)
neighbor_count += 1.f;
}
if (row < height - 1) {
unsigned char pixelbelow = row_pointers[row + 1][i];
if (pixelbelow == lastpixel)
neighbor_count += 1.f;
}
i++;
}
while (lastcol <= col) {
float e = edges[row * width + lastcol] / 255.f;
e *= 1.f - 2.5f / neighbor_count;
edges[row * width + lastcol++] = e * 255.f;
}
lastpixel = px;
}
}
}
input_image->dither_map = input_image->edges;
input_image->edges = NULL;
}
static colormap *
add_fixed_colors_to_palette (colormap * palette, const int max_colors,
const f_pixel fixed_colors[], const int fixed_colors_count,
void *(*malloc) (size_t), void (*free) (void *))
{
colormap *newpal;
unsigned int i, palette_max;
int j;
if (!fixed_colors_count)
return palette;
newpal =
pam_colormap (MIN (max_colors,
(palette ? palette->colors : 0) + fixed_colors_count), malloc, free);
i = 0;
if (palette && fixed_colors_count < max_colors) {
palette_max = MIN (palette->colors, max_colors - fixed_colors_count);
for (; i < palette_max; i++) {
newpal->palette[i] = palette->palette[i];
}
}
for (j = 0; j < MIN (max_colors, fixed_colors_count); j++) {
newpal->palette[i++] = (colormap_item) {
.acolor = fixed_colors[j],.fixed = true,};
}
if (palette)
pam_freecolormap (palette);
return newpal;
}
static void
adjust_histogram_callback (hist_item * item, float diff)
{
item->adjusted_weight =
(item->perceptual_weight + item->adjusted_weight) * (sqrtf (1.f + diff));
}
/**
Repeats mediancut with different histogram weights to find palette with minimum error.
feedback_loop_trials controls how long the search will take. < 0 skips the iteration.
*/
static colormap *
find_best_palette (histogram * hist, const liq_attr * options,
const double max_mse, const f_pixel fixed_colors[],
const unsigned int fixed_colors_count, double *palette_error_p)
{
unsigned int max_colors = options->max_colors;
// if output is posterized it doesn't make sense to aim for perfrect colors, so increase target_mse
// at this point actual gamma is not set, so very conservative posterization estimate is used
const double target_mse = MIN (max_mse, MAX (options->target_mse,
pow ((1 << options->min_posterization_output) / 1024.0, 2)));
int feedback_loop_trials = options->feedback_loop_trials;
colormap *acolormap = NULL;
double least_error = MAX_DIFF;
double target_mse_overshoot = feedback_loop_trials > 0 ? 1.05 : 1.0;
const double percent =
(double) (feedback_loop_trials > 0 ? feedback_loop_trials : 1) / 100.0;
do {
colormap *newmap;
double total_error;
if (hist->size && fixed_colors_count < max_colors) {
newmap =
mediancut (hist, options->min_opaque_val,
max_colors - fixed_colors_count, target_mse * target_mse_overshoot,
MAX (MAX (90.0 / 65536.0, target_mse), least_error) * 1.2,
options->malloc, options->free);
} else {
feedback_loop_trials = 0;
newmap = NULL;
}
newmap =
add_fixed_colors_to_palette (newmap, max_colors, fixed_colors,
fixed_colors_count, options->malloc, options->free);
if (!newmap) {
return NULL;
}
if (feedback_loop_trials <= 0) {
return newmap;
}
// after palette has been created, total error (MSE) is calculated to keep the best palette
// at the same time Voronoi iteration is done to improve the palette
// and histogram weights are adjusted based on remapping error to give more weight to poorly matched colors
{
const bool first_run_of_target_mse = !acolormap && target_mse > 0;
total_error =
viter_do_iteration (hist, newmap, options->min_opaque_val,
first_run_of_target_mse ? NULL : adjust_histogram_callback, !acolormap
|| options->fast_palette);
}
// goal is to increase quality or to reduce number of colors used if quality is good enough
if (!acolormap || total_error < least_error || (total_error <= target_mse
&& newmap->colors < max_colors)) {
if (acolormap)
pam_freecolormap (acolormap);
acolormap = newmap;
if (total_error < target_mse && total_error > 0) {
// voronoi iteration improves quality above what mediancut aims for
// this compensates for it, making mediancut aim for worse
target_mse_overshoot =
MIN (target_mse_overshoot * 1.25, target_mse / total_error);
}
least_error = total_error;
// if number of colors could be reduced, try to keep it that way
// but allow extra color as a bit of wiggle room in case quality can be improved too
max_colors = MIN (newmap->colors + 1, max_colors);
feedback_loop_trials -= 1; // asymptotic improvement could make it go on forever
} else {
for (unsigned int j = 0; j < hist->size; j++) {
hist->achv[j].adjusted_weight =
(hist->achv[j].perceptual_weight +
hist->achv[j].adjusted_weight) / 2.0;
}
target_mse_overshoot = 1.0;
feedback_loop_trials -= 6;
// if error is really bad, it's unlikely to improve, so end sooner
if (total_error > least_error * 4)
feedback_loop_trials -= 3;
pam_freecolormap (newmap);
}
liq_verbose_printf (options, " selecting colors...%d%%", 100 - MAX (0,
(int) (feedback_loop_trials / percent)));
}
while (feedback_loop_trials > 0);
*palette_error_p = least_error;
return acolormap;
}
static liq_result *
pngquant_quantize (histogram * hist, const liq_attr * options,
const liq_image * img)
{
colormap *acolormap;
double palette_error = -1;
// no point having perfect match with imperfect colors (ignorebits > 0)
const bool fast_palette = options->fast_palette || hist->ignorebits > 0;
const bool few_input_colors =
hist->size + img->fixed_colors_count <= options->max_colors;
liq_result *result;
// If image has few colors to begin with (and no quality degradation is required)
// then it's possible to skip quantization entirely
if (few_input_colors && options->target_mse == 0) {
acolormap = pam_colormap (hist->size, options->malloc, options->free);
for (unsigned int i = 0; i < hist->size; i++) {
acolormap->palette[i].acolor = hist->achv[i].acolor;
acolormap->palette[i].popularity = hist->achv[i].perceptual_weight;
}
acolormap =
add_fixed_colors_to_palette (acolormap, options->max_colors,
img->fixed_colors, img->fixed_colors_count, options->malloc,
options->free);
palette_error = 0;
} else {
const double max_mse = options->max_mse * (few_input_colors ? 0.33 : 1.0); // when degrading image that's already paletted, require much higher improvement, since pal2pal often looks bad and there's little gain
const double iteration_limit = options->voronoi_iteration_limit;
unsigned int iterations = options->voronoi_iterations;
acolormap =
find_best_palette (hist, options, max_mse, img->fixed_colors,
img->fixed_colors_count, &palette_error);
if (!acolormap) {
return NULL;
}
// Voronoi iteration approaches local minimum for the palette
if (!iterations && palette_error < 0 && max_mse < MAX_DIFF)
iterations = 1; // otherwise total error is never calculated and MSE limit won't work
if (iterations) {
double previous_palette_error = MAX_DIFF;
unsigned int i;
// likely_colormap_index (used and set in viter_do_iteration) can't point to index outside colormap
if (acolormap->colors < 256)
for (unsigned int j = 0; j < hist->size; j++) {
if (hist->achv[j].tmp.likely_colormap_index >= acolormap->colors) {
hist->achv[j].tmp.likely_colormap_index = 0; // actual value doesn't matter, as the guess is out of date anyway
}
}
verbose_print (options, " moving colormap towards local minimum");
for (i = 0; i < iterations; i++) {
palette_error =
viter_do_iteration (hist, acolormap, options->min_opaque_val, NULL,
i == 0 || options->fast_palette);
if (fabs (previous_palette_error - palette_error) < iteration_limit) {
break;
}
if (palette_error > max_mse * 1.5) { // probably hopeless
if (palette_error > max_mse * 3.0)
break; // definitely hopeless
i++;
}
previous_palette_error = palette_error;
}
}
if (palette_error > max_mse) {
liq_verbose_printf (options,
" image degradation MSE=%.3f (Q=%d) exceeded limit of %.3f (%d)",
palette_error * 65536.0 / 6.0, mse_to_quality (palette_error),
max_mse * 65536.0 / 6.0, mse_to_quality (max_mse));
pam_freecolormap (acolormap);
return NULL;
}
}
sort_palette (acolormap, options);
result = options->malloc (sizeof (liq_result));
if (!result)
return NULL;
*result = (liq_result) {
.magic_header = liq_result_magic,.malloc = options->malloc,.free =
options->free,.palette = acolormap,.palette_error =
palette_error,.fast_palette = fast_palette,.use_dither_map =
options->use_dither_map,.gamma =
img->gamma,.min_posterization_output =
options->min_posterization_output,};
return result;
}
LIQ_EXPORT liq_error
liq_write_remapped_image (liq_result * result, liq_image * input_image,
void *buffer, size_t buffer_size)
{
size_t required_size;
unsigned char **rows;
unsigned char *buffer_bytes;
unsigned i;
if (!CHECK_STRUCT_TYPE (result, liq_result)) {
return LIQ_INVALID_POINTER;
}
if (!CHECK_STRUCT_TYPE (input_image, liq_image)) {
return LIQ_INVALID_POINTER;
}
if (!CHECK_USER_POINTER (buffer)) {
return LIQ_INVALID_POINTER;
}
required_size = input_image->width * input_image->height;
if (buffer_size < required_size) {
return LIQ_BUFFER_TOO_SMALL;
}
rows = g_alloca (sizeof (unsigned char *) * input_image->height);
buffer_bytes = buffer;
for (i = 0; i < input_image->height; i++) {
rows[i] = &buffer_bytes[input_image->width * i];
}
return liq_write_remapped_image_rows (result, input_image, rows);
}
LIQ_EXPORT liq_error
liq_write_remapped_image_rows (liq_result * quant, liq_image * input_image,
unsigned char **row_pointers)
{
unsigned int i;
liq_remapping_result *result;
float remapping_error;
if (!CHECK_STRUCT_TYPE (quant, liq_result))
return LIQ_INVALID_POINTER;
if (!CHECK_STRUCT_TYPE (input_image, liq_image))
return LIQ_INVALID_POINTER;
for (i = 0; i < input_image->height; i++) {
if (!CHECK_USER_POINTER (row_pointers + i)
|| !CHECK_USER_POINTER (row_pointers[i]))
return LIQ_INVALID_POINTER;
}
if (quant->remapping) {
liq_remapping_result_destroy (quant->remapping);
}
result = quant->remapping = liq_remapping_result_create (quant);
if (!result)
return LIQ_OUT_OF_MEMORY;
if (!input_image->edges && !input_image->dither_map && quant->use_dither_map) {
contrast_maps (input_image);
}
/*
** Step 4: map the colors in the image to their closest match in the
** new colormap, and write 'em out.
*/
remapping_error = result->palette_error;
if (result->dither_level == 0) {
set_rounded_palette (&result->int_palette, result->palette, result->gamma,
quant->min_posterization_output);
remapping_error =
remap_to_palette (input_image, row_pointers, result->palette,
quant->fast_palette);
} else {
const bool generate_dither_map = result->use_dither_map
&& (input_image->edges && !input_image->dither_map);
if (generate_dither_map) {
// If dithering (with dither map) is required, this image is used to find areas that require dithering
remapping_error =
remap_to_palette (input_image, row_pointers, result->palette,
quant->fast_palette);
update_dither_map (row_pointers, input_image);
}
// remapping above was the last chance to do voronoi iteration, hence the final palette is set after remapping
set_rounded_palette (&result->int_palette, result->palette, result->gamma,
quant->min_posterization_output);
remap_to_palette_floyd (input_image, row_pointers, result->palette,
MAX (remapping_error * 2.4, 16.f / 256.f), result->use_dither_map,
generate_dither_map, result->dither_level);
}
// remapping error from dithered image is absurd, so always non-dithered value is used
// palette_error includes some perceptual weighting from histogram which is closer correlated with dssim
// so that should be used when possible.
if (result->palette_error < 0) {
result->palette_error = remapping_error;
}
return LIQ_OK;
}
LIQ_EXPORT int
liq_version (void)
{
return LIQ_VERSION;
}
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