// 源码出自：潇湘夜雨
<!DOCTYPE>
<html>
<head>
<meta charset="utf-8"/>
</head>
<body>
<img src="" id='stuPic' style="display:none">
<input type="file" id="loadFile">
<canvas id="canvas" width="600" height="600"></canvas>
<script src="http://code.jquery.com/jquery-latest.js"></script>
<script>
var canvas = document.getElementById('canvas');
var context = canvas.getContext('2d');
function grey(image){
var imagedata = context.getImageData(0,0,image.width,image.height);
var imagedata1 = context.createImageData(image.width,image.height);
var pix = imagedata.data;
for (var i = 0, n = pix.length; i < n; i += 4) {
var grayscale = pix[i] * .3 + pix[i+1] * .59 + pix[i+2] * .11;
pix[i] = grayscale; // red
pix[i+1] = grayscale; // green
pix[i+2] = grayscale; // blue
// alpha
}
context.putImageData(imagedata, 0, 0);
}
$("#loadFile").change(function(){
var file = $(this)[0].files[0];
var fReader = new FileReader();
fReader.readAsDataURL(file);
fReader.onload = function (e){
$("#stuPic").attr("src", this.result).load(function(){
context.drawImage(this,0,0);
var s = context.getImageData(100,50,350,150);
grey(this);
context.putImageData(s,100,50);
});
};
});
</script>
</body>
</html>