<!DOCTYPE html>
<html>
<body>
<img id="scream" src="img_the_scream.jpg" alt="The Scream" width="220" height="277">
<canvas id="myCanvas" width="220" height="277" style="border:1px solid #d3d3d3;">
Your browser does not support the HTML5 canvas tag.</canvas>
<script>
document.getElementById("scream").onload = function() {
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
var img = document.getElementById("scream");
ctx.drawImage(img, 0, 0);
var imgData = ctx.getImageData(0, 0, c.width, c.height);
// invert colors
var i;
for (i = 0; i < imgData.data.length; i += 4) {
imgData.data[i] = 255 - imgData.data[i];
imgData.data[i+1] = 255 - imgData.data[i+1];
imgData.data[i+2] = 255 - imgData.data[i+2];
imgData.data[i+3] = 255;
}
ctx.putImageData(imgData, 0, 0);
};
</script>
</body>
</html>