JS实现马赛克图片效果

整体逻辑:获取oldImg图片的像素信息,以5*5为单位,在5*5单位中取到一个随机像素并赋值给5*5中的所有像素点,加以循环,以实现马赛克效果。


<html>

    <head>
        <meta charset="UTF-8">
        <title>title>
        <style type="text/css">
            * {
                margin: 0;
                padding: 0;
            }

            body {
                background-color: grey;
                text-align: center;
            }

            #myCanvas {
                background-color: rgba(250, 0, 0, 0.3);
            }
        style>
    head>

    <body>
        <canvas id="myCanvas" width="500" height="400">canvas>
    body>
    <script type="text/javascript">
        window.onload = function() {
            var myCanvas = document.getElementById('myCanvas');
            var painting = myCanvas.getContext('2d');
              //生成一个图片节点
            var imgNode = new Image();
            imgNode.src = '1.jpg';
            //调用函数
            drawImg(imgNode);

            function drawImg(imgNode) {
                //图片加载后执行马赛克实现语句:5个一组取到随机像素赋给新图里的五个一组
                imgNode.onload = function() {
                    painting.drawImage(imgNode, 0, 0, 250, 400);

                    var size = 5;
                    //获取老图所有像素点
                    var oldImg = painting.getImageData(0, 0, 250, 400)
                    //创建新图像素对象
                    var newImg = painting.createImageData(250, 400)

                    for(var i = 0; i < oldImg.width; i++) {
                        for(var j = 0; j < oldImg.height; j++) {
                            //从5*5中获取单个像素信息
                            var color = getPxInfo(oldImg, Math.floor(i * size + Math.random() * size), Math.floor(j * size + Math.random() * size))

                            //写入单个像素信息
                            for(var a = 0; a < size; a++) {
                                for(var b = 0; b < size; b++) {
                                    //                            (a,b)
                                    setPxInfo(newImg, i * size + a, j * size + b, color);
                                }
                            }

                        }

                    }
                    painting.putImageData(newImg, 250, 0)
                }
            }

            //读取单个像素信息
            function getPxInfo(imgDate, x, y) {
                var colorArr = [];

                var width = imgDate.width;

                colorArr[0] = imgDate.data[(width * y + x) * 4 + 0]
                colorArr[1] = imgDate.data[(width * y + x) * 4 + 1]
                colorArr[2] = imgDate.data[(width * y + x) * 4 + 2]
                colorArr[3] = imgDate.data[(width * y + x) * 4 + 3]

                return colorArr;

            }

            //写入单个像素信息
            function setPxInfo(imgDate, x, y, colors) {
                //(x,y) 之前有多少个像素点  ==  width*y + x
                var width = imgDate.width;

                imgDate.data[(width * y + x) * 4 + 0] = colors[0];
                imgDate.data[(width * y + x) * 4 + 1] = colors[1];
                imgDate.data[(width * y + x) * 4 + 2] = colors[2];
                imgDate.data[(width * y + x) * 4 + 3] = colors[3];

            }

        }
    script>

html>

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