1 files changed, 52 insertions, 0 deletions
diff --git a/src/render_assets.rs b/src/render_assets.rs
new file mode 100644
index 0000000..1615e01
--- /dev/null
+++ b/src/render_assets.rs
@@ -0,0 +1,52 @@
+use bevy::{prelude::*, render::{render_asset::{RenderAsset, RenderAssets, RenderAssetUsages, PrepareAssetError}, render_resource::{Buffer, Extent3d, BufferUsages, BufferDescriptor, TextureFormat}, renderer::RenderDevice}, ecs::system::{lifetimeless::SRes, SystemParamItem}};
+
+pub struct GpuFramebufferExtractSource {
+    pub buffer: Buffer,
+    pub source_handle: Handle<Image>,
+    pub source_size: Extent3d,
+    pub bytes_per_row: u32,
+    pub padded_bytes_per_row: u32,
+    pub format: TextureFormat,
+}
+
+#[derive(Asset, Reflect, Clone, Default)]
+pub struct FramebufferExtractSource(pub Handle<Image>);
+
+impl RenderAsset for FramebufferExtractSource {
+    type PreparedAsset = GpuFramebufferExtractSource;
+    type Param = (SRes<RenderDevice>, SRes<RenderAssets<Image>>);
+
+    fn asset_usage(&self) -> RenderAssetUsages {
+        RenderAssetUsages::default()
+    }
+
+    fn prepare_asset(
+        self,
+        (device, images): &mut SystemParamItem<Self::Param>,
+    ) -> Result<Self::PreparedAsset, PrepareAssetError<Self>> {
+        
+        let Some(gpu_image) = images.get(&self.0) else {
+            warn!("Failed to get GPU image");
+            return Err(PrepareAssetError::RetryNextUpdate(self))
+        };
+
+        let size = gpu_image.texture.size();
+        let format = gpu_image.texture_format;
+        let bytes_per_row = (size.width / format.block_dimensions().0) * format.block_copy_size(None).unwrap();
+        let padded_bytes_per_row = RenderDevice::align_copy_bytes_per_row(bytes_per_row as usize) as u32;
+
+        Ok(GpuFramebufferExtractSource {
+            buffer: device.create_buffer(&BufferDescriptor { 
+                label: Some("framebuffer_extract_buffer"),
+                size: (size.height * padded_bytes_per_row) as u64,
+                usage: BufferUsages::COPY_DST | BufferUsages::MAP_READ,
+                mapped_at_creation: false,
+            }),
+            source_handle: self.0.clone(),
+            source_size: size,
+            bytes_per_row,
+            padded_bytes_per_row,
+            format,
+        })
+    }
+}