From ab7682178796a37c38aa3149f47d3e8193e08e29 Mon Sep 17 00:00:00 2001
From: Tj Holowaychuk <tj@vision-media.ca>
Date: Mon, 29 Nov 2010 09:40:40 -0800
Subject: [PATCH] pre-multiply putImageData() components

---
 src/CanvasRenderingContext2d.cc | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/src/CanvasRenderingContext2d.cc b/src/CanvasRenderingContext2d.cc
index 5b15bd6..8c68473 100644
--- a/src/CanvasRenderingContext2d.cc
+++ b/src/CanvasRenderingContext2d.cc
@@ -459,12 +459,13 @@ Context2d::PutImageData(const Arguments &args) {
       uint8_t r = srcRows[bx + 0];
       uint8_t g = srcRows[bx + 1];
       uint8_t b = srcRows[bx + 2];
+      float alpha = (float) a / 255;
 
       // ARGB
       *pixel = a << 24
-        | r << 16
-        | g << 8
-        | b;
+        | (int)((float) r * alpha) << 16
+        | (int)((float) g * alpha) << 8
+        | (int)((float) b * alpha);
     }
     srcRows += srcStride;
   }