Move readback format mapping to renderer gl

src/renderer_gl/opengl_capabilities.cpp

@@ -123,6 +123,32 @@ OpenGlPixelFormat texture_format_for_channel_count(std::uint32_t channel_count)
     }
 }
 
+OpenGlReadbackFormat rgba8_readback_format() noexcept
+{
+    return OpenGlReadbackFormat {
+        .pixel_format = gl_rgba,
+        .component_type = gl_unsigned_byte,
+        .bytes_per_pixel = 4U,
+    };
+}
+
+OpenGlReadbackFormat rgba32f_readback_format() noexcept
+{
+    return OpenGlReadbackFormat {
+        .pixel_format = gl_rgba,
+        .component_type = gl_float,
+        .bytes_per_pixel = 16U,
+    };
+}
+
+std::uint64_t readback_byte_count(
+    OpenGlReadbackFormat format,
+    std::uint32_t width,
+    std::uint32_t height) noexcept
+{
+    return static_cast<std::uint64_t>(width) * height * format.bytes_per_pixel;
+}
+
 const char* framebuffer_status_name(std::uint32_t status) noexcept
 {
     switch (status) {

src/renderer_gl/opengl_capabilities.h

@@ -32,12 +32,24 @@ struct OpenGlTextureParameter {
     std::uint32_t value = 0;
 };
 
+struct OpenGlReadbackFormat {
+    std::uint32_t pixel_format = 0;
+    std::uint32_t component_type = 0;
+    std::uint32_t bytes_per_pixel = 0;
+};
+
 [[nodiscard]] OpenGlCapabilities detect_opengl_capabilities(
     std::span<const std::string_view> extensions,
     OpenGlRuntime runtime) noexcept;
 
 [[nodiscard]] std::uint32_t texture_upload_type_for_internal_format(std::uint32_t internal_format) noexcept;
 [[nodiscard]] OpenGlPixelFormat texture_format_for_channel_count(std::uint32_t channel_count) noexcept;
+[[nodiscard]] OpenGlReadbackFormat rgba8_readback_format() noexcept;
+[[nodiscard]] OpenGlReadbackFormat rgba32f_readback_format() noexcept;
+[[nodiscard]] std::uint64_t readback_byte_count(
+    OpenGlReadbackFormat format,
+    std::uint32_t width,
+    std::uint32_t height) noexcept;
 [[nodiscard]] const char* framebuffer_status_name(std::uint32_t status) noexcept;
 [[nodiscard]] std::uint32_t framebuffer_color_buffer_mask() noexcept;
 [[nodiscard]] std::uint32_t framebuffer_blit_filter(bool linear) noexcept;