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createImageData.html
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<!DOCTYPE html>
<html lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<meta name="viewport" content="initial-scale=1.0, maximum-scale=1.0, user-scalable=0">
<link rel="stylesheet" href="main.css">
</head>
<body>
<canvas id="canvas"></canvas>
<script>
var ca = document.getElementsByTagName('canvas')[0],
ctx = ca.getContext('2d');
ca.width = document.body.clientWidth;
ca.height = document.body.clientHeight;
var imageData = ctx.createImageData(200, 200),
pixels = imageData.data;
for (var i = 0, len = (imageData.width * imageData.height); i < len; i++) {
pixels[i * 4] = Math.floor(Math.random() * 255);
pixels[i * 4 + 1] = Math.floor(Math.random() * 255);
pixels[i * 4 + 2] = Math.floor(Math.random() * 255);
pixels[i * 4 + 3] = Math.floor(Math.random() * 255);
}
ctx.putImageData(imageData, 0, 0);
var imageData2 = ctx.createImageData(500, 500),
pixels2 = imageData2.data;
var numTileRows = 10,
numTileCols = 10;
var tileWidth = imageData2.width / numTileRows,
tileHeight = imageData2.height / numTileCols;
for (var r = 0; r < numTileRows; r++) {
for (var c = 0; c < numTileCols; c++) {
var red = Math.floor(Math.random() * 255),
green = Math.floor(Math.random() * 255),
blue = Math.floor(Math.random() * 255);
var avg = (red + green + blue) / 3;
for (var tr = 0; tr < tileHeight; tr++) {
for (var tc = 0; tc < tileWidth; tc++) {
var trueX = (c * tileWidth) + tc,
trueY = (r * tileHeight) + tr;
var pos = (trueY * (imageData2.width * 4) + (trueX * 4));
// pixels2[pos] = red;
// pixels2[pos + 1] = green;
// pixels2[pos + 2] = blue;
pixels2[pos + 3] = '255';
pixels2[pos] = avg;
pixels2[pos + 1] = avg;
pixels2[pos + 2] = avg;
}
}
}
}
ctx.putImageData(imageData2, 0, 250);
</script>
</body>
</html>