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<!DOCTYPE html>
<body>
</body>
<script>
/*
Compare how the opacity is handled in different blend modes when setting its
value with filters or with properties.
*/
function drawSquares(canvasId, x, y, compositeOperation) {
var canvas = document.getElementById(canvasId);
var ctx = canvas.getContext('2d');
canvas.style.position = 'absolute';
canvas.style.left = `${x}px`;
canvas.style.top = `${y}px`;
ctx.globalCompositeOperation = 'source-over';
ctx.globalAlpha = 1.0;
ctx.fillStyle = 'green';
ctx.fillRect(0, 0, 200, 60);
ctx.fillStyle = 'blue';
ctx.fillRect(0, 0, 50, 50);
ctx.globalAlpha = 0.7;
ctx.fillStyle = 'red';
ctx.fillRect(50, 0, 50, 50);
ctx.globalCompositeOperation = compositeOperation;
ctx.globalAlpha = 0.5;
ctx.fillStyle = 'yellow';
ctx.fillRect(25, 25, 50, 50);
}
// Fomatted in the same matrix as the drawn elements.
var compositeOperations =
['source-over', 'source-in', 'source-out', 'source-atop','destination-over',
'destination-in', 'destination-out', 'destination-atop', 'lighter', 'copy',
'xor', 'multiply', 'screen', 'overlay', 'darken',
'lighten', 'color-dodge', 'color-burn', 'hard-light', 'soft-light',
'difference', 'exclusion', 'hue', 'saturation', 'color',
'luminosity'];
for (var i = 0; i < compositeOperations.length; i++){
var canvas = document.createElement('canvas');
canvas.id = `canvas-${i}`;
document.body.appendChild(canvas);
drawSquares(canvas.id, (i%5)*300, Math.floor(i/5)*300,
compositeOperations[i]);
}
</script>
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