From 1ec3c341cc4416a35714ccecfb9e9e6a4bc1d283 Mon Sep 17 00:00:00 2001
From: Nicholas Nethercote <nnethercote@mozilla.com>
Date: Thu, 27 Feb 2014 21:15:38 -0800
Subject: [PATCH] Put mask data to the canvas in small slices.
---
src/display/canvas.js | 50 +++++++++++++++++++++++++------------------
1 file changed, 29 insertions(+), 21 deletions(-)
diff --git a/src/display/canvas.js b/src/display/canvas.js
index 7381aa691..f94483b47 100644
--- a/src/display/canvas.js
+++ b/src/display/canvas.js
@@ -532,31 +532,39 @@ var CanvasGraphics = (function CanvasGraphicsClosure() {
}
function putBinaryImageMask(ctx, imgData) {
- var width = imgData.width, height = imgData.height;
- var tmpImgData = ctx.createImageData(width, height);
- var data = imgData.data;
- var tmpImgDataPixels = tmpImgData.data;
- var dataPos = 0;
+ var height = imgData.height, width = imgData.width;
+ var fullChunkHeight = 16;
+ var fracChunks = height / fullChunkHeight;
+ var fullChunks = Math.floor(fracChunks);
+ var totalChunks = Math.ceil(fracChunks);
+ var partialChunkHeight = height - fullChunks * fullChunkHeight;
- // Expand the mask so it can be used by the canvas. Any required inversion
- // has already been handled.
- var tmpPos = 3; // alpha component offset
- for (var i = 0; i < height; i++) {
- var mask = 0;
- for (var j = 0; j < width; j++) {
- if (!mask) {
- var elem = data[dataPos++];
- mask = 128;
+ var chunkImgData = ctx.createImageData(width, fullChunkHeight);
+ var srcPos = 0;
+ var src = imgData.data;
+ var dest = chunkImgData.data;
+
+ for (var i = 0; i < totalChunks; i++) {
+ var thisChunkHeight =
+ (i < fullChunks) ? fullChunkHeight : partialChunkHeight;
+
+ // Expand the mask so it can be used by the canvas. Any required
+ // inversion has already been handled.
+ var destPos = 3; // alpha component offset
+ for (var j = 0; j < thisChunkHeight; j++) {
+ var mask = 0;
+ for (var k = 0; k < width; k++) {
+ if (!mask) {
+ var elem = src[srcPos++];
+ mask = 128;
+ }
+ dest[destPos] = (elem & mask) ? 0 : 255;
+ destPos += 4;
+ mask >>= 1;
}
- if (!(elem & mask)) {
- tmpImgDataPixels[tmpPos] = 255;
- }
- tmpPos += 4;
- mask >>= 1;
}
+ ctx.putImageData(chunkImgData, 0, i * fullChunkHeight);
}
-
- ctx.putImageData(tmpImgData, 0, 0);
}
function copyCtxState(sourceCtx, destCtx) {