add Canvas.decode static method

src/coders/imageio.cpp

@@ -1,3 +1,4 @@
+#define VC_ENABLE_REFLECTION
 #include "imageio.hpp"
 
 #include <functional>
@@ -7,28 +8,34 @@
 #include "io/io.hpp"
 #include "png.hpp"
 
+using namespace imageio;
+
 using image_reader =
     std::function<std::unique_ptr<ImageData>(const ubyte*, size_t)>;
 using image_writer = std::function<void(const std::string&, const ImageData*)>;
 
-static std::unordered_map<std::string, image_reader> readers {
-    {".png", png::load_image},
+static std::unordered_map<ImageFileFormat, image_reader> readers {
+    {ImageFileFormat::PNG, png::load_image},
 };
 
-static std::unordered_map<std::string, image_writer> writers {
-    {".png", png::write_image},
+static std::unordered_map<ImageFileFormat, image_writer> writers {
+    {ImageFileFormat::PNG, png::write_image},
 };
 
 bool imageio::is_read_supported(const std::string& extension) {
-    return readers.find(extension) != readers.end();
+    return extension == ".png";
 }
 
 bool imageio::is_write_supported(const std::string& extension) {
-    return writers.find(extension) != writers.end();
+    return extension == ".png";
 }
 
 std::unique_ptr<ImageData> imageio::read(const io::path& file) {
-    auto found = readers.find(file.extension());
+    ImageFileFormat format;
+    if (!ImageFileFormatMeta.getItem(file.extension().substr(1), format)) {
+        throw std::runtime_error("unsupported image format");
+    }
+    auto found = readers.find(format);
     if (found == readers.end()) {
         throw std::runtime_error(
             "file format is not supported (read): " + file.string()
@@ -44,8 +51,25 @@ std::unique_ptr<ImageData> imageio::read(const io::path& file) {
     }
 }
 
+std::unique_ptr<ImageData> imageio::decode(
+    ImageFileFormat format, util::span<ubyte> src
+) {
+    auto found = readers.find(format);
+    try {
+        return std::unique_ptr<ImageData>(found->second(src.data(), src.size()));
+    } catch (const std::runtime_error& err) {
+        throw std::runtime_error(
+            "could not to decode image: " + std::string(err.what())
+        );
+    }
+}
+
 void imageio::write(const io::path& file, const ImageData* image) {
-    auto found = writers.find(file.extension());
+    ImageFileFormat format;
+    if (!ImageFileFormatMeta.getItem(file.extension().substr(1), format)) {
+        throw std::runtime_error("unsupported image format");
+    }
+    auto found = writers.find(format);
     if (found == writers.end()) {
         throw std::runtime_error(
             "file format is not supported (write): " + file.string()

src/coders/imageio.hpp

@@ -6,6 +6,8 @@
 #include "io/fwd.hpp"
 #include "util/Buffer.hpp"
 #include "util/EnumMetadata.hpp"
+#include "util/span.hpp"
+#include "typedefs.hpp"
 
 class ImageData;
 
@@ -25,5 +27,6 @@ namespace imageio {
 
     std::unique_ptr<ImageData> read(const io::path& file);
     void write(const io::path& file, const ImageData* image);
+    std::unique_ptr<ImageData> decode(ImageFileFormat format, util::span<ubyte> src);
     util::Buffer<unsigned char> encode(ImageFileFormat format, const ImageData& image);
 }