html5 上传头像的裁剪

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：

<!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：

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();

    }

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html5 上传头像的裁剪

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