HTML5 canvas实现移动端上传头像拖拽裁剪效果

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本示例使用HTML5 canvas，简单的编写了上传头像的裁剪效果，移动端支持拖拽后裁剪，虽然样式不好看，但是功能还算全：

下图为裁剪后的效果：

html部分：

XML/HTML Code复制内容到剪贴板

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>上传头像</title>
<meta name="renderer" content="webkit">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
</head>
<body>
<div id="imgCrop" style="width:200px;height:200px;border:1px solid #ccc;overflow:hidden;">
<img src="img/test.jpg" alt="">
</div>
<input type="file" accept="image/*" />
<button id="save">保存</button>
<p>下面为剪切的图片:</p>
<div id="imgShow"></div>
</body>
</html>

JavaScript部分：

JavaScript Code复制内容到剪贴板

var $imgCrop = $("#imgCrop");
var $img = $imgCrop.find("img");
var img = $img[0];
var width = parseInt($imgCrop.css("width"));
var height = parseInt($imgCrop.css("height"));
var startX,startY,scale = 1;
var x = 0,y = 0;
$("input").on("change",function(){
var fr = new FileReader();
var file = this.files[0]
//console.log(file);
if(!/image\/\w+/.test(file.type)){
alert(file.name + "不是图片文件！");
return;
}
console.log(file);
$img.removeAttr("height width");
fr.readAsDataURL(file);
fr.onload = function(){
img.src = fr.result;
var widthInit = img.width;
if(img.width>img.height){
img.height = height;
x = (width - img.width)/2;
y = 0;
}else{
img.width = width;
x = 0;
y = (height - img.height)/2;
}
scale = widthInit/img.width;
move($img, x, y);
};
});
img.addEventListener("touchstart",function(e){
startX = e.targetTouches[0].pageX;
startY = e.targetTouches[0].pageY;
return;
});
img.addEventListener("touchmove",function(e){
e.preventDefault();
e.stopPropagation();
var changeX = e.changedTouches[0].pageX - startX + x;
var changeY = e.changedTouches[0].pageY - startY + y;
move($(this), changeX, changeY);
return;
});
img.addEventListener("touchend",function(e){
var changeX = e.changedTouches[0].pageX - startX + x;
var changeY = e.changedTouches[0].pageY - startY + y;
x = x + e.changedTouches[0].pageX - startX;
y = y + e.changedTouches[0].pageY - startY;
move($(this), changeX, changeY);
return;
});
//确定目标图片的样式
function move(ele, x, y){
ele.css({
'-webkit-transform' : 'translate3d(' + x + 'px, ' + y + 'px, 0)',
'transform' : 'translate3d(' + x + 'px, ' + y + 'px, 0)'
});
}
$("#save").on("click",function(){
var url = imageData($img);
console.log(url);
$("#imgShow").html("<img src="+url+" />");;
});
//裁剪图片
function imageData($img) {
var canvas = document.createElement('canvas');
var ctx = canvas.getContext('2d');
canvas.width = width ;
canvas.height = height;
ctx.drawImage(img, -x*scale, -y*scale, width*scale, height*scale, 0, 0, width, height);
return canvas.toDataURL();
}