/* 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 #include #include #include #include #include #include #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 #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; va_start(va, fmt); int required_space = vsnprintf(NULL, 0, fmt, va)+1; // +\0 va_end(va); char buf[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() { #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) { 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. char 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) { 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 const double extra_low_quality_fudge = MAX(0,0.016/(0.001+quality) - 0.001); 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) { for(int 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) { if (!CHECK_STRUCT_TYPE(attr, liq_attr)) return LIQ_INVALID_POINTER; if (speed < 1 || speed > 10) return LIQ_VALUE_OUT_OF_RANGE; int 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() { 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) { if (!CHECK_STRUCT_TYPE(orig, liq_attr)) { return NULL; } liq_attr *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); if (!ptr) { return NULL; } uintptr_t 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*)) { #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 } liq_attr *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) { if (!CHECK_STRUCT_TYPE(img, liq_image)) return LIQ_INVALID_POINTER; if (img->fixed_colors_count > 255) return LIQ_BUFFER_TOO_SMALL; float gamma_lut[256]; to_f_set_gamma(gamma_lut, img->gamma); img->fixed_colors[img->fixed_colors_count++] = to_f(gamma_lut, (rgba_pixel){ .r = color.r, .g = color.g, .b = color.b, .a = color.a, }); 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) { 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; } liq_image *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) { if (!check_image_size(attr, width, height)) { return NULL; } if (!CHECK_USER_POINTER(bitmap)) { liq_log_error(attr, "invalid bitmap pointer"); return NULL; } rgba_pixel *pixels = bitmap; rgba_pixel **rows = attr->malloc(sizeof(rows[0])*height); if (!rows) return NULL; for(int i=0; i < height; i++) { rows[i] = pixels + width * i; } liq_image *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) { if (liq_image_can_use_rows(img)) { return img->rows[row]; } assert(img->temp_row); rgba_pixel *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); for(unsigned int 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]; to_f_set_gamma(gamma_lut, img->gamma); f_pixel *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*); 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) { 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; } histogram *hist = get_histogram(img, attr); if (!hist) { return NULL; } liq_result *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) { if (!CHECK_STRUCT_TYPE(result, liq_result)) { return NULL; } liq_remapping_result *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) { /* ** 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(unsigned int 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 */ unsigned int num_transparent=0; for(unsigned int 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<> (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; } 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 = omp_get_max_threads(); viter_state average_color[(VITER_CACHE_LINE_GAP+map->colors) * max_threads]; 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(int 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(unsigned int 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 ratio = 1.0; // 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); float 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! ;) const float 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); /* 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 (unsigned int 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) { memset(nexterr, 0, (cols + 2) * sizeof(*nexterr)); unsigned int col = (fs_direction) ? 0 : (cols - 1); const f_pixel *const row_pixels = liq_image_get_row_f(input_image, row); do { float dither_level = base_dithering_level; if (dither_map) { dither_level *= dither_map[row*cols + col]; } const f_pixel spx = get_dithered_pixel(dither_level, max_dither_error, thiserr[col + 1], row_pixels[col]); const unsigned int 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); const f_pixel xp = acolormap[last_match].acolor; f_pixel err = { .r = (spx.r - xp.r), .g = (spx.g - xp.g), .b = (spx.b - xp.b), .a = (spx.a - 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); 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 } histogram *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; if (cols < 4 || rows < 4 || (3*cols*rows) > LIQ_HIGH_MEMORY_LIMIT) { return; } unsigned char *restrict noise = image->malloc(cols*rows); unsigned char *restrict edges = image->malloc(cols*rows); unsigned char *restrict tmp = image->malloc(cols*rows); if (!noise || !edges || !tmp) { return; } const f_pixel *curr_row, *prev_row, *next_row; curr_row = prev_row = next_row = liq_image_get_row_f(image, 0); for (int j=0; j < rows; j++) { prev_row = curr_row; curr_row = next_row; next_row = liq_image_get_row_f(image, MIN(rows-1,j+1)); f_pixel prev, curr = curr_row[0], next=curr; for (int 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*)) { if (!fixed_colors_count) return palette; colormap *newpal = pam_colormap(MIN(max_colors, (palette ? palette->colors : 0) + fixed_colors_count), malloc, free); unsigned int i=0; if (palette && fixed_colors_count < max_colors) { unsigned int palette_max = MIN(palette->colors, max_colors - fixed_colors_count); for(; i < palette_max; i++) { newpal->palette[i] = palette->palette[i]; } } for(int 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<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; 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; double 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; // 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 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 const double iteration_limit = options->voronoi_iteration_limit; unsigned int iterations = options->voronoi_iterations; 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) { // 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"); double previous_palette_error = MAX_DIFF; for(unsigned int 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); liq_result *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) { 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; } const size_t required_size = input_image->width * input_image->height; if (buffer_size < required_size) { return LIQ_BUFFER_TOO_SMALL; } unsigned char *rows[input_image->height]; unsigned char *buffer_bytes = buffer; for(unsigned int 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) { if (!CHECK_STRUCT_TYPE(quant, liq_result)) return LIQ_INVALID_POINTER; if (!CHECK_STRUCT_TYPE(input_image, liq_image)) return LIQ_INVALID_POINTER; for(unsigned int 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); } liq_remapping_result *const 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. */ float 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() { return LIQ_VERSION; }