Add assets PNG metadata tests

src/assets/image_metadata.cpp

@@ -0,0 +1,146 @@
+#include "assets/image_metadata.h"
+
+#include <cstddef>
+
+namespace pp::assets {
+
+namespace {
+
+constexpr std::byte png_signature[] {
+    std::byte { 0x89 },
+    std::byte { 0x50 },
+    std::byte { 0x4e },
+    std::byte { 0x47 },
+    std::byte { 0x0d },
+    std::byte { 0x0a },
+    std::byte { 0x1a },
+    std::byte { 0x0a },
+};
+
+[[nodiscard]] bool has_png_signature(std::span<const std::byte> bytes) noexcept
+{
+    if (bytes.size() < 8U) {
+        return false;
+    }
+
+    for (std::size_t i = 0; i < 8U; ++i) {
+        if (bytes[i] != png_signature[i]) {
+            return false;
+        }
+    }
+
+    return true;
+}
+
+[[nodiscard]] std::uint32_t read_u32_be(std::span<const std::byte> bytes, std::size_t offset) noexcept
+{
+    return (static_cast<std::uint32_t>(std::to_integer<std::uint8_t>(bytes[offset])) << 24U)
+        | (static_cast<std::uint32_t>(std::to_integer<std::uint8_t>(bytes[offset + 1U])) << 16U)
+        | (static_cast<std::uint32_t>(std::to_integer<std::uint8_t>(bytes[offset + 2U])) << 8U)
+        | static_cast<std::uint32_t>(std::to_integer<std::uint8_t>(bytes[offset + 3U]));
+}
+
+[[nodiscard]] pp::foundation::Result<ImageColorType> parse_png_color_type(std::byte value) noexcept
+{
+    switch (std::to_integer<std::uint8_t>(value)) {
+    case 0:
+        return pp::foundation::Result<ImageColorType>::success(ImageColorType::grayscale);
+    case 2:
+        return pp::foundation::Result<ImageColorType>::success(ImageColorType::rgb);
+    case 3:
+        return pp::foundation::Result<ImageColorType>::success(ImageColorType::indexed);
+    case 4:
+        return pp::foundation::Result<ImageColorType>::success(ImageColorType::grayscale_alpha);
+    case 6:
+        return pp::foundation::Result<ImageColorType>::success(ImageColorType::rgba);
+    default:
+        return pp::foundation::Result<ImageColorType>::failure(
+            pp::foundation::Status::invalid_argument("PNG color type is unsupported"));
+    }
+}
+
+[[nodiscard]] std::uint8_t component_count(ImageColorType color_type) noexcept
+{
+    switch (color_type) {
+    case ImageColorType::grayscale:
+    case ImageColorType::indexed:
+        return 1;
+    case ImageColorType::grayscale_alpha:
+        return 2;
+    case ImageColorType::rgb:
+        return 3;
+    case ImageColorType::rgba:
+        return 4;
+    }
+
+    return 0;
+}
+
+}
+
+pp::foundation::Result<ImageMetadata> parse_png_metadata(std::span<const std::byte> bytes) noexcept
+{
+    constexpr std::size_t png_ihdr_end = 33;
+    if (bytes.size() < png_ihdr_end) {
+        return pp::foundation::Result<ImageMetadata>::failure(
+            pp::foundation::Status::out_of_range("PNG metadata is truncated"));
+    }
+
+    if (!has_png_signature(bytes)) {
+        return pp::foundation::Result<ImageMetadata>::failure(
+            pp::foundation::Status::invalid_argument("PNG signature is invalid"));
+    }
+
+    const auto ihdr_length = read_u32_be(bytes, 8);
+    if (ihdr_length != 13U || bytes[12] != std::byte { 'I' } || bytes[13] != std::byte { 'H' }
+        || bytes[14] != std::byte { 'D' } || bytes[15] != std::byte { 'R' }) {
+        return pp::foundation::Result<ImageMetadata>::failure(
+            pp::foundation::Status::invalid_argument("PNG IHDR chunk is invalid"));
+    }
+
+    const auto width = read_u32_be(bytes, 16);
+    const auto height = read_u32_be(bytes, 20);
+    if (width == 0 || height == 0 || width > max_image_dimension || height > max_image_dimension) {
+        return pp::foundation::Result<ImageMetadata>::failure(
+            pp::foundation::Status::out_of_range("PNG dimensions are outside the configured range"));
+    }
+
+    const auto bit_depth = std::to_integer<std::uint8_t>(bytes[24]);
+    if (bit_depth == 0U) {
+        return pp::foundation::Result<ImageMetadata>::failure(
+            pp::foundation::Status::invalid_argument("PNG bit depth is invalid"));
+    }
+
+    const auto color_type = parse_png_color_type(bytes[25]);
+    if (!color_type) {
+        return pp::foundation::Result<ImageMetadata>::failure(color_type.status());
+    }
+
+    return pp::foundation::Result<ImageMetadata>::success(ImageMetadata {
+        .width = width,
+        .height = height,
+        .bit_depth = bit_depth,
+        .components = component_count(color_type.value()),
+        .color_type = color_type.value(),
+    });
+}
+
+const char* image_color_type_name(ImageColorType color_type) noexcept
+{
+    switch (color_type) {
+    case ImageColorType::grayscale:
+        return "grayscale";
+    case ImageColorType::rgb:
+        return "rgb";
+    case ImageColorType::indexed:
+        return "indexed";
+    case ImageColorType::grayscale_alpha:
+        return "grayscale_alpha";
+    case ImageColorType::rgba:
+        return "rgba";
+    }
+
+    return "unknown";
+}
+
+}