Support reading arbitrary image formats via stb_image

libs/gfx/CMakeLists.txt

@@ -1,7 +1,7 @@
 find_file(KHR_PLATFORM_FILE KHR/khrplatform.h)
 
-file(GLOB_RECURSE PSEMEK_GFX_HEADERS RELATIVE "${CMAKE_CURRENT_SOURCE_DIR}" "include/*.hpp")
+file(GLOB_RECURSE PSEMEK_GFX_HEADERS RELATIVE "${CMAKE_CURRENT_SOURCE_DIR}" "include/*.hpp" "include/*.h")
-file(GLOB_RECURSE PSEMEK_GFX_SOURCES RELATIVE "${CMAKE_CURRENT_SOURCE_DIR}" "source/*.cpp")
+file(GLOB_RECURSE PSEMEK_GFX_SOURCES RELATIVE "${CMAKE_CURRENT_SOURCE_DIR}" "source/*.cpp" "source/*.c")
 
 psemek_add_library(psemek-gfx ${PSEMEK_GFX_HEADERS} ${PSEMEK_GFX_SOURCES} "${CMAKE_CURRENT_SOURCE_DIR}/api/${PSEMEK_GL_API}/source/gl.cpp")
 target_include_directories(psemek-gfx PUBLIC "${CMAKE_CURRENT_SOURCE_DIR}/include" "${CMAKE_CURRENT_SOURCE_DIR}/api/${PSEMEK_GL_API}/include")

libs/gfx/include/psemek/gfx/pixmap.hpp

@@ -29,6 +29,13 @@ namespace psemek::gfx
 
 	void write_png(pixmap_rgba const & p, io::ostream && os);
 
+	template <typename Pixel>
+	basic_pixmap<Pixel> read_image(io::istream && is);
+
+	extern template pixmap_monochrome read_image<std::uint8_t>(io::istream && is);
+	extern template pixmap_rgb read_image<color_rgb>(io::istream && is);
+	extern template pixmap_rgba read_image<color_rgba>(io::istream && is);
+
 	template <typename Pixel, std::size_t N>
 	auto to_srgb(util::array<Pixel, N> pm, float g = 1.f / 2.2f)
 	{

libs/gfx/source/detail/stb_image.c

@@ -0,0 +1,7 @@
+#define STB_IMAGE_IMPLEMENTATION
+#define STBI_FAILURE_USERMSG
+
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wunused-but-set-variable"
+#include <psemek/gfx/detail/stb_image.h>
+#pragma GCC diagnostic pop

libs/gfx/source/pixmap.cpp

@@ -0,0 +1,54 @@
+#include <psemek/gfx/pixmap.hpp>
+#include <psemek/gfx/detail/stb_image.h>
+#include <psemek/util/exception.hpp>
+
+namespace psemek::gfx
+{
+
+	template <typename Pixel>
+	basic_pixmap<Pixel> read_image(io::istream && is)
+	{
+		stbi_io_callbacks callbacks;
+
+		callbacks.read = [](void * user, char * data, int size) -> int
+		{
+			return reinterpret_cast<io::istream *>(user)->read(data, size);
+		};
+
+		callbacks.skip = [](void * user, int count)
+		{
+			if (count < 0)
+				throw util::exception("unget is not supported in stb_image skip callback");
+
+			char buffer[1024];
+			while (count > 0)
+			{
+				int read_count = std::min(1024, count);
+				count -= reinterpret_cast<io::istream *>(user)->read(buffer, read_count);
+			}
+		};
+
+		callbacks.eof = [](void * user)
+		{
+			return reinterpret_cast<io::istream *>(user)->finished() ? 1 : 0;
+		};
+
+		int width, height, channels;
+		auto data = stbi_load_from_callbacks(&callbacks, &is, &width, &height, &channels, sizeof(Pixel));
+
+		if (!data)
+			throw util::exception(stbi_failure_reason());
+
+		basic_pixmap<Pixel> result({width, height});
+		std::copy(data, data + width * height * sizeof(Pixel), reinterpret_cast<stbi_uc *>(result.data()));
+
+		stbi_image_free(data);
+
+		return result;
+	}
+
+	template pixmap_monochrome read_image<std::uint8_t>(io::istream && is);
+	template pixmap_rgb read_image<color_rgb>(io::istream && is);
+	template pixmap_rgba read_image<color_rgba>(io::istream && is);
+
+}