e342766cbf
It's not possible to share them across threads, so in case we decide to use multithreading in the future, it's best to mark them as thread_local right away, even if it's a no-op right now.
217 lines
8.6 KiB
C++
217 lines
8.6 KiB
C++
#include <emscripten/bind.h>
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#include <emscripten/val.h>
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#include <inttypes.h>
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#include <limits.h>
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#include <math.h>
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#include <stdlib.h>
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#include "libimagequant.h"
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using namespace emscripten;
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int version() {
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return (((LIQ_VERSION / 10000) % 100) << 16) | (((LIQ_VERSION / 100) % 100) << 8) |
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(((LIQ_VERSION / 1) % 100) << 0);
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}
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thread_local const val Uint8ClampedArray = val::global("Uint8ClampedArray");
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#define liq_ptr(T) std::unique_ptr<T, std::integral_constant<decltype(&T##_destroy), T##_destroy>>
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using liq_attr_ptr = liq_ptr(liq_attr);
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using liq_image_ptr = liq_ptr(liq_image);
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using liq_result_ptr = liq_ptr(liq_result);
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liq_result_ptr liq_image_quantize(liq_image* image, liq_attr* attr) {
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liq_result* res = nullptr;
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liq_image_quantize(image, attr, &res);
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return liq_result_ptr(res);
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}
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val quantize(std::string rawimage,
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int image_width,
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int image_height,
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int num_colors,
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float dithering) {
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auto image_buffer = (const liq_color*)rawimage.c_str();
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int size = image_width * image_height;
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liq_attr_ptr attr(liq_attr_create());
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liq_image_ptr image(
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liq_image_create_rgba(attr.get(), image_buffer, image_width, image_height, 0));
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liq_set_max_colors(attr.get(), num_colors);
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auto res = liq_image_quantize(image.get(), attr.get());
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liq_set_dithering_level(res.get(), dithering);
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std::vector<uint8_t> image8bit(size);
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std::vector<liq_color> result(size);
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liq_write_remapped_image(res.get(), image.get(), image8bit.data(), image8bit.size());
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auto pal = liq_get_palette(res.get());
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// Turn palletted image back into an RGBA image
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for (int i = 0; i < size; i++) {
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result[i] = pal->entries[image8bit[i]];
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}
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return Uint8ClampedArray.new_(
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typed_memory_view(result.size() * sizeof(liq_color), (const uint8_t*)result.data()));
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}
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const liq_color zx_colors[] = {
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{.r = 0, .g = 0, .b = 0, .a = 255}, // regular black
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{.r = 0, .g = 0, .b = 215, .a = 255}, // regular blue
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{.r = 215, .g = 0, .b = 0, .a = 255}, // regular red
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{.r = 215, .g = 0, .b = 215, .a = 255}, // regular magenta
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{.r = 0, .g = 215, .b = 0, .a = 255}, // regular green
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{.r = 0, .g = 215, .b = 215, .a = 255}, // regular cyan
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{.r = 215, .g = 215, .b = 0, .a = 255}, // regular yellow
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{.r = 215, .g = 215, .b = 215, .a = 255}, // regular white
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{.r = 0, .g = 0, .b = 255, .a = 255}, // bright blue
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{.r = 255, .g = 0, .b = 0, .a = 255}, // bright red
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{.r = 255, .g = 0, .b = 255, .a = 255}, // bright magenta
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{.r = 0, .g = 255, .b = 0, .a = 255}, // bright green
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{.r = 0, .g = 255, .b = 255, .a = 255}, // bright cyan
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{.r = 255, .g = 255, .b = 0, .a = 255}, // bright yellow
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{.r = 255, .g = 255, .b = 255, .a = 255} // bright white
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};
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/**
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* The ZX has one bit per pixel, but can assign two colours to an 8x8 block. The
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* two colours must both be 'regular' or 'bright'. Black exists as both regular
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* and bright.
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*/
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val zx_quantize(std::string rawimage, int image_width, int image_height, float dithering) {
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auto image_buffer = (const liq_color*)rawimage.c_str();
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int size = image_width * image_height;
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liq_color block[8 * 8];
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uint8_t image8bit[8 * 8];
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std::vector<liq_color> result(size);
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// For each 8x8 grid
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for (int block_start_y = 0; block_start_y < image_height; block_start_y += 8) {
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for (int block_start_x = 0; block_start_x < image_width; block_start_x += 8) {
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int color_popularity[15] = {0};
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int block_index = 0;
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int block_width = 8;
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int block_height = 8;
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// If the block hangs off the right/bottom of the image dimensions, make
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// it smaller to fit.
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if (block_start_y + block_height > image_height) {
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block_height = image_height - block_start_y;
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}
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if (block_start_x + block_width > image_width) {
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block_width = image_width - block_start_x;
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}
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// For each pixel in that block:
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for (int y = block_start_y; y < block_start_y + block_height; y++) {
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for (int x = block_start_x; x < block_start_x + block_width; x++) {
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int pixel_start = (y * image_width) + x;
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int smallest_distance = INT_MAX;
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int winning_index = -1;
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// Copy pixel data for quantizing later
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block[block_index++] = image_buffer[pixel_start];
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// Which zx color is this pixel closest to?
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for (int color_index = 0; color_index < 15; color_index++) {
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liq_color color = zx_colors[color_index];
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liq_color pixel = image_buffer[pixel_start];
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// Using Euclidean distance. LibQuant has better methods, but it
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// requires conversion to LAB, so I don't think it's worth it.
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int distance =
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pow(color.r - pixel.r, 2) + pow(color.g - pixel.g, 2) + pow(color.b - pixel.b, 2);
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if (distance < smallest_distance) {
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winning_index = color_index;
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smallest_distance = distance;
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}
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}
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color_popularity[winning_index]++;
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}
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}
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// Get the three most popular colours for the block.
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int first_color_index = 0;
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int second_color_index = 0;
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int third_color_index = 0;
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int highest_popularity = -1;
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int second_highest_popularity = -1;
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int third_highest_popularity = -1;
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for (int color_index = 0; color_index < 15; color_index++) {
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if (color_popularity[color_index] > highest_popularity) {
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// Store this as the most popular pixel, and demote the current
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// values:
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third_color_index = second_color_index;
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third_highest_popularity = second_highest_popularity;
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second_color_index = first_color_index;
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second_highest_popularity = highest_popularity;
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first_color_index = color_index;
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highest_popularity = color_popularity[color_index];
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} else if (color_popularity[color_index] > second_highest_popularity) {
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third_color_index = second_color_index;
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third_highest_popularity = second_highest_popularity;
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second_color_index = color_index;
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second_highest_popularity = color_popularity[color_index];
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} else if (color_popularity[color_index] > third_highest_popularity) {
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third_color_index = color_index;
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third_highest_popularity = color_popularity[color_index];
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}
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}
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// ZX images can't mix bright and regular colours, except black which
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// appears in both. Resolve any conflict:
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while (1) {
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// If either colour is black, there's no conflict to resolve.
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if (first_color_index != 0 && second_color_index != 0) {
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if (first_color_index >= 8 && second_color_index < 8) {
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// Make the second color bright
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second_color_index = second_color_index + 7;
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} else if (first_color_index < 8 && second_color_index >= 8) {
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// Make the second color regular
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second_color_index = second_color_index - 7;
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}
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}
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// If, during conflict resolving, we now have two of the same colour
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// (because we initially selected the bright & regular version of the
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// same colour), retry again with the third most popular colour.
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if (first_color_index == second_color_index) {
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second_color_index = third_color_index;
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} else
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break;
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}
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// Quantize
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liq_attr_ptr attr(liq_attr_create());
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liq_image_ptr image(liq_image_create_rgba(attr.get(), block, block_width, block_height, 0));
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liq_set_max_colors(attr.get(), 2);
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liq_image_add_fixed_color(image.get(), zx_colors[first_color_index]);
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liq_image_add_fixed_color(image.get(), zx_colors[second_color_index]);
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auto res = liq_image_quantize(image.get(), attr.get());
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liq_set_dithering_level(res.get(), dithering);
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liq_write_remapped_image(res.get(), image.get(), image8bit, size);
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auto pal = liq_get_palette(res.get());
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// Turn palletted image back into an RGBA image, and write it into the
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// full size result image.
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for (int y = 0; y < block_height; y++) {
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for (int x = 0; x < block_width; x++) {
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int image8BitPos = y * block_width + x;
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int resultStartPos = ((block_start_y + y) * image_width) + (block_start_x + x);
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result[resultStartPos] = pal->entries[image8bit[image8BitPos]];
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}
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}
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}
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}
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return Uint8ClampedArray.new_(
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typed_memory_view(result.size() * sizeof(liq_color), (const uint8_t*)result.data()));
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}
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EMSCRIPTEN_BINDINGS(my_module) {
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function("quantize", &quantize);
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function("zx_quantize", &zx_quantize);
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function("version", &version);
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}
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