Canvas 颜色反转

ImageData中的元素反转颜色 255-data[i,i+1,i+2]

<!DOCTYPE html>

<html lang="en">

<head>

    <meta charset="UTF-8">

    <title>converse color</title>

</head>

<body>

    <canvas id='myCanvas' width='800' height='600'>

        your browser does not support canvas

    </canvas>

    <script type="text/javascript">

    var c = document.getElementById('myCanvas');

    var ctx = c.getContext('2d');

    var img = new Image();

    img.src = 'face.jpg';

    img.onload = function() {

        ctx.drawImage(img, 0, 0);

        var imgData = ctx.getImageData(0, 0, 250, 250);

        var pixels = imgData.data;

        for (var i = 0, n = pixels.length; i < n; i += 4) {

            pixels[i] = 255 - pixels[i];

            pixels[i + 1] = 255 - pixels[i + 1];

            pixels[i + 2] = 255 - pixels[i + 2];

        }

        ctx.putImageData(imgData, 250, 0);

    };

    </script>

</body>

</html>

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Canvas 颜色反转

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