<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>www.jb51.net JS图片马赛克</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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