gpuweb · kainino0x · Jun 4, 2019 · Apr 10, 2019
diff --git a/design/ImageBitmapToTexture.md b/design/ImageBitmapToTexture.md
@@ -0,0 +1,37 @@
+# WebGPU + ImageBitmap
+
+```webidl
+dictionary ImageBitmapCopyView {
+    ImageBitmap imageBitmap;
+    GPUOrigin2D origin;
+};
+
+partial interface GPUCommandEncoder {
+    void copyImageBitmapToTexture(
+        ImageBitmapCopyView source,
+        GPUTextureCopyView destination,
+        // For now, copySize.z must be 1.
+        GPUExtent3D copySize);
+};
+```
+
+`copyImageBitmapToTexture` encodes a copy from a source sub-rectangle of an `ImageBitmap` into a destination sub-resource of a `GPUTexture`.
+When the command buffer is submitted, the `ImageBitmap` must not be detached.
+If it is, a validation error is generated.
+
+## Alternatives Considered
+
+  * Creating a `GPUTexture` directly from an `ImageBitmap`, attempting to avoid copies, is impractical because it requires the GPUTexture's format to match the internal representation of the `ImageBitmap`, which is not exposed to the Web platform.
+    Additionally, `ImageBitmap`s may be GPU- or CPU-backed, and wrapping a CPU-backed `ImageBitmap` is a significant meta-operation that requires an additional copy to be submitted.
+
+## Issues
+
+  * Some of the `ImageBitmap` creation options, such as `"flipY"`, have semantics that have to match the target graphics API where the data is intended to be used.
+    For WebGL, `imageOrientation: "flipY"` is necessary to ensure that the resulting `WebGLTexture` is oriented correctly.
+    For WebGPU, it may be the case that texture origins are defined differently from WebGL, necessitating `imageOrientation: "none"`.
+    These cases will have to be thoroughly tested.
+
+  * The browser may choose an internal representation for an `ImageBitmap` which is not ideal for usage by WebGPU (or, for that matter, [by WebGL](https://crbug.com/831740)).
+    This could result in texture uploads being significantly more expensive than necessary due to per-pixel data swizzling during upload.
+    Providing any hint about the intended usage of the `ImageBitmap` during its construction (for example "for use with WebGL" or "for use with this WebGPU adapter") would require changes to the HTML specification.
+    Attempts to change Chrome's internal representation of `ImageBitmap` have not yet been successful; it's not clear how feasible it would be in other browsers.
diff --git a/spec/index.bs b/spec/index.bs
@@ -30,6 +30,11 @@ dictionary GPUColor {
     required float a;
 };
 
+dictionary GPUOrigin2D {
+    u32 x = 0;
+    u32 y = 0;
+};
+
 dictionary GPUOrigin3D {
     u32 x = 0;
     u32 y = 0;
@@ -691,6 +696,11 @@ dictionary GPUTextureCopyView {
     GPUOrigin3D origin;  // defaults to {x: 0, y: 0, z: 0}
 };
 
+dictionary ImageBitmapCopyView {
+    ImageBitmap imageBitmap;
+    GPUOrigin2D origin;
+};
+
 interface GPUCommandBuffer : GPUObjectBase {
 };
 
@@ -721,6 +731,12 @@ interface GPUCommandEncoder : GPUObjectBase {
         GPUTextureCopyView destination,
         GPUExtent3D copySize);
 
+    void copyImageBitmapToTexture(
+        ImageBitmapCopyView source,
+        GPUTextureCopyView destination,
+        // For now, copySize.z must be 1.
+        GPUExtent3D copySize);
+
     // Debugging assistance
     void pushDebugGroup(DOMString groupLabel);
     void popDebugGroup();