feat(shader-ast-stdlib): add pre/postmultiplyAlpha() fns

thi-ng · Jan 4, 2023 · 367ebbd · 367ebbd
1 parent f5bbcc8
commit 367ebbd
Showing 1 changed file with 6 additions and 0 deletions.
diff --git a/packages/shader-ast-stdlib/src/color/porter-duff.ts b/packages/shader-ast-stdlib/src/color/porter-duff.ts
@@ -53,6 +53,12 @@ export const porterDuff = (
 		];
 	});
 
+export const premultiplyAlpha = (col: Vec4Sym) =>
+	vec4(mul($xyz(col), $w(col)), $w(col));
+
+export const postmultiplyAlpha = (col: Vec4Sym) =>
+	vec4(div($xyz(col), $w(col)), $w(col));
+
 // coefficient functions
 
 export const ZERO = () => FLOAT0;