Switch image textures to premultiplied alpha

csmartdalton · csmartdalton · blakdragan7 · csmartdalton · commit c459f8b9d727 · 2025-04-05T04:27:24.000Z
The renderer intentionally chose unmultiplied alpha for gradients, in order to not lose color information with transparent stops. But for this very same reason, we need *premultiplied* alpha for image textures. Otherwise, the (transparent) background color can bleed into edges. Switch image textures to premultiplied, while keeping gradients unmultiplied.

Diffs=
a70f0f84dd Switch image textures to premultiplied alpha (#9377)

Co-authored-by: Chris Dalton &lt;99840794+csmartdalton@users.noreply.github.com&gt;
Co-authored-by: blakdragan7 &lt;jcopela4@Gmail.com&gt;
diff --git a/.rive_head b/.rive_head
@@ -1 +1 @@
-9d516a9ece7c618a9ca4c861baefcd963497d2e0
+a70f0f84dda65ddd956b1229b9530aed37f44b18
diff --git a/wasm/src/bindings_webgl2.cpp b/wasm/src/bindings_webgl2.cpp
@@ -124,7 +124,9 @@ EM_JS(void, upload_image, (EMSCRIPTEN_WEBGL_CONTEXT_HANDLE gl, uintptr_t renderI
         return;
     }
     gl = GL.getContext(gl).GLctx;
+    gl.pixelStorei(gl.UNPACK_PREMULTIPLY_ALPHA_WEBGL, true);
     gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, image);
+    gl.pixelStorei(gl.UNPACK_PREMULTIPLY_ALPHA_WEBGL, false);
 });
 
 EM_JS(void, delete_image, (uintptr_t renderImage), {
diff --git a/wasm/submodules/rive-runtime b/wasm/submodules/rive-runtime
@@ -1 +1 @@
-Subproject commit 6e162b26f95b213e8f260ff5543c45d0298c6a74
+Subproject commit da39c5608dc3711d1412744e03a02b95f33f14af

Original file line number	Diff line number	Diff line change
`@@ -1 +1 @@`
`1`		`-9d516a9ece7c618a9ca4c861baefcd963497d2e0`
	`1`	`+a70f0f84dda65ddd956b1229b9530aed37f44b18`
Original file line number	Diff line number	Diff line change
`@@ -124,7 +124,9 @@ EM_JS(void, upload_image, (EMSCRIPTEN_WEBGL_CONTEXT_HANDLE gl, uintptr_t renderI`
`124`	`124`	`return;`
`125`	`125`	`}`
`126`	`126`	`gl = GL.getContext(gl).GLctx;`
	`127`	`+ gl.pixelStorei(gl.UNPACK_PREMULTIPLY_ALPHA_WEBGL, true);`
`127`	`128`	`gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, image);`
	`129`	`+ gl.pixelStorei(gl.UNPACK_PREMULTIPLY_ALPHA_WEBGL, false);`
`128`	`130`	`});`
`129`	`131`
`130`	`132`	`EM_JS(void, delete_image, (uintptr_t renderImage), {`