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https://github.com/gbdev/rgbds.git
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Support PNG-format palette spec files (#1764)
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Rangi
GitHub
@@ -9,6 +9,7 @@
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#include <inttypes.h>
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#include <limits.h>
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#include <optional>
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#include <png.h>
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#include <stdint.h>
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#include <stdio.h>
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#include <streambuf>
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@@ -578,6 +579,208 @@ static void parseGBCFile(std::filebuf &file) {
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}
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}
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[[noreturn]]
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static void handlePngError(png_structp, char const *msg) {
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fatal("Error reading palette file: %s", msg);
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}
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static void handlePngWarning(png_structp, char const *msg) {
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warnx("In palette file: %s", msg);
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}
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static void readPngData(png_structp png, png_bytep data, size_t length) {
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std::filebuf *file = reinterpret_cast<std::filebuf *>(png_get_io_ptr(png));
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std::streamsize expectedLen = length;
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std::streamsize nbBytesRead = file->sgetn(reinterpret_cast<char *>(data), expectedLen);
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if (nbBytesRead != expectedLen) {
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fatal(
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"Error reading palette file: file too short (expected at least %zd more bytes after "
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"reading %zu)",
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length - nbBytesRead,
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static_cast<size_t>(file->pubseekoff(0, std::ios_base::cur))
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);
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}
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}
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static bool checkPngSwatch(std::vector<png_byte> const &image, uint32_t base, uint32_t swatchSize) {
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Rgba topLeft(image[base], image[base + 1], image[base + 2], image[base + 3]);
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uint32_t rowFactor = swatchSize * options.nbColorsPerPal;
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for (uint32_t y = 0; y < swatchSize; y++) {
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for (uint32_t x = 0; x < swatchSize; x++) {
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if (x == 0 && y == 0) {
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continue;
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}
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uint32_t offset = base + (y * rowFactor + x) * 4;
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Rgba pixel(image[offset], image[offset + 1], image[offset + 2], image[offset + 3]);
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if (pixel != topLeft) {
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return false;
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}
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}
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}
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return true;
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}
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static void parsePNGFile(std::filebuf &file) {
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std::array<unsigned char, 8> pngHeader;
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if (file.sgetn(reinterpret_cast<char *>(pngHeader.data()), pngHeader.size())
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!= static_cast<std::streamsize>(pngHeader.size()) // Not enough bytes?
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|| png_sig_cmp(pngHeader.data(), 0, pngHeader.size()) != 0) {
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// LCOV_EXCL_START
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error("Palette file does not appear to be a PNG palette file");
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return;
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// LCOV_EXCL_STOP
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}
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png_structp png =
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png_create_read_struct(PNG_LIBPNG_VER_STRING, nullptr, handlePngError, handlePngWarning);
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if (!png) {
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// LCOV_EXCL_START
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error("Failed to create PNG read structure: %s", strerror(errno));
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return;
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// LCOV_EXCL_STOP
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}
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png_infop info = png_create_info_struct(png);
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Defer destroyPng{[&] { png_destroy_read_struct(&png, &info, nullptr); }};
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if (!info) {
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// LCOV_EXCL_START
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error("Failed to create PNG info structure: %s", strerror(errno));
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return;
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// LCOV_EXCL_STOP
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}
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png_set_read_fn(png, &file, readPngData);
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png_set_sig_bytes(png, pngHeader.size());
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// Process all chunks up to but not including the image data
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png_read_info(png, info);
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uint32_t width, height;
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int bitDepth, colorType, interlaceType;
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png_get_IHDR(
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png, info, &width, &height, &bitDepth, &colorType, &interlaceType, nullptr, nullptr
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);
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png_colorp embeddedPal = nullptr;
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int nbColors;
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png_bytep transparencyPal = nullptr;
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int nbTransparentEntries;
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if (png_get_PLTE(png, info, &embeddedPal, &nbColors) != 0) {
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if (png_get_tRNS(png, info, &transparencyPal, &nbTransparentEntries, nullptr)) {
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assume(nbTransparentEntries <= nbColors);
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}
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}
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// Set up transformations to turn everything into RGBA888 for simplicity of handling
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// Convert grayscale to RGB
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switch (colorType & ~PNG_COLOR_MASK_ALPHA) {
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case PNG_COLOR_TYPE_GRAY:
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png_set_gray_to_rgb(png); // This also converts tRNS to alpha
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break;
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case PNG_COLOR_TYPE_PALETTE:
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png_set_palette_to_rgb(png);
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break;
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}
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if (png_get_valid(png, info, PNG_INFO_tRNS)) {
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// If we read a tRNS chunk, convert it to alpha
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png_set_tRNS_to_alpha(png);
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} else if (!(colorType & PNG_COLOR_MASK_ALPHA)) {
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// Otherwise, if we lack an alpha channel, default to full opacity
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png_set_add_alpha(png, 0xFFFF, PNG_FILLER_AFTER);
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}
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// Scale 16bpp back to 8 (we don't need all of that precision anyway)
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if (bitDepth == 16) {
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png_set_scale_16(png);
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} else if (bitDepth < 8) {
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png_set_packing(png);
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}
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if (interlaceType != PNG_INTERLACE_NONE) {
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png_set_interlace_handling(png);
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}
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// Update `info` with the transformations
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png_read_update_info(png, info);
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// These shouldn't have changed
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assume(png_get_image_width(png, info) == width);
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assume(png_get_image_height(png, info) == height);
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// These should have changed, however
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assume(png_get_color_type(png, info) == PNG_COLOR_TYPE_RGBA);
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assume(png_get_bit_depth(png, info) == 8);
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// Now that metadata has been read, we can process the image data
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std::vector<png_byte> image(width * height * 4);
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std::vector<png_bytep> rowPtrs(height);
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for (uint32_t y = 0; y < height; ++y) {
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rowPtrs[y] = image.data() + y * width * 4;
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}
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png_read_image(png, rowPtrs.data());
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// The image width must evenly divide into a color swatch for each color per palette
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if (width % options.nbColorsPerPal != 0) {
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error(
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"PNG palette file is %" PRIu32 "x%" PRIu32 ", which is not a multiple of %" PRIu8
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" color swatches wide",
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width,
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height,
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options.nbColorsPerPal
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);
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return;
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}
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// Infer the color swatch size (width and height) from the image width
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uint32_t swatchSize = width / options.nbColorsPerPal;
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// The image height must evenly divide into a color swatch for each palette
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if (height % swatchSize != 0) {
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error(
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"PNG palette file is %" PRIu32 "x%" PRIu32 ", which is not a multiple of %" PRIu32
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" pixels high",
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width,
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height,
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swatchSize
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);
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return;
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}
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// More palettes than the maximum are a warning, not an error
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uint32_t nbPals = height / swatchSize;
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if (nbPals > options.nbPalettes) {
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warnx(
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"PNG palette file contains %" PRIu32 " palette rows, but there can only be %" PRIu16
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"; ignoring extra",
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nbPals,
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options.nbPalettes
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);
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nbPals = options.nbPalettes;
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}
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options.palSpec.clear();
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// Get each color from the top-left pixel of each swatch
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uint32_t colorFactor = swatchSize * 4;
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uint32_t palFactor = swatchSize * options.nbColorsPerPal;
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for (uint32_t palIdx = 0; palIdx < nbPals; ++palIdx) {
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options.palSpec.emplace_back();
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for (uint32_t colorIdx = 0; colorIdx < options.nbColorsPerPal; ++colorIdx) {
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std::optional<Rgba> &color = options.palSpec.back()[colorIdx];
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uint32_t offset = (palIdx * palFactor + colorIdx) * colorFactor;
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color = Rgba(image[offset], image[offset + 1], image[offset + 2], image[offset + 3]);
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// Check that each swatch is completely one color
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if (!checkPngSwatch(image, offset, swatchSize)) {
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error("PNG palette file uses multiple colors in one color swatch");
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return;
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}
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}
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}
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}
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void parseExternalPalSpec(char const *arg) {
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// `fmt:path`, parse the file according to the given format
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@@ -596,6 +799,7 @@ void parseExternalPalSpec(char const *arg) {
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std::tuple{"ACT", &parseACTFile, std::ios::binary},
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std::tuple{"ACO", &parseACOFile, std::ios::binary},
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std::tuple{"GBC", &parseGBCFile, std::ios::binary},
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std::tuple{"PNG", &parsePNGFile, std::ios::binary},
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};
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auto iter = std::find_if(RANGE(parsers), [&arg, &ptr](auto const &parser) {
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