Using HTML5's globalCompositeOperation "xor" with shape and text elements in Chrome
I have run into an issue when attempting to globalCompositeOperation to mask/blend shapes and text (shapes mask/blended with other shapes works just fine) in Chrome (more specifically I am using Chrome 12.0.7). Can anyone suggest where I might have gone astray here or suggest a workaround within the canvas element?
Here is an image showing what I'm开发者_运维知识库 seeing: http://i.stack.imgur.com/wRunv.jpg
Here is the code that will reproduce these results:
<!DOCTYPE HTML>
<html>
<body>
<canvas id="testCanvas" width="500" height="500"></canvas>
<script type="text/javascript">
// setup canvas
var tcanvas = document.getElementById("testCanvas");
var tcontext = tcanvas.getContext("2d");
// draw square
tcontext.fillStyle = "#FF3366";
tcontext.fillRect(15,15,70,70);
// set composite property
tcontext.globalCompositeOperation = "xor";
// draw text
tcontext.fillStyle="#0099FF";
tcontext.font = "35px sans-serif";
tcontext.fillText("test", 22, 25);
</script>
</body>
</html>
seems like the XOR globalCompositeOperation problem is a chrome bug that happens only with fillText.
Other drawing methods seem to work, see here: http://jsfiddle.net/Y5wvb/
You should report this bug to the Chromium project: http://code.google.com/p/chromium/issues/list
When you do, post the url of the posted issue here to we can vote it up :)
I found out that if you change the order of drawing, e.g. draw the text before filling the rectangle, the XOR works just fine. see here: http://jsfiddle.net/Y5wvb/1/
加载中,请稍侯......
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