H5实现图片优化上传

一，HTML部分

<input type="file" accept="images/*">
<input class="url" type="url" placeholder="url">
<div class="container"></div>
<button class="submit">Submit</button>

二，CSS部分

.container{
    width: 300px;
}
.resizer{
    overflow: hidden;
}
.resizer.have-img button.ok{
    display: inline-block;
}
.resizer.have-img .inner {
    display: block;
}
.inner{
    width: 100%;
    position: relative;
    font-size: 0;
    overflow: hidden;
    display: none;
}
img{
    width: 100%;
}

.frames{
    position: absolute;
    top: 0;
    left: 0;
    border: 1px solid black;
    cursor: move;
    outline: rgba(0, 0, 0, 0.6) solid 10000px;
}
button.ok{
    float:right;
    margin-left: 5px;
    display: none;
}
canvas{
    max-width: 100%;
    margin:auto;
    display: block;
}

三，JS部分（重点）

var tmp=$('<div class="resizer">'+
          '<div class="inner">'+
          '<img>'+
          '<div class="frames"></div>'+
          '</div>'+
          //'<button>&#10007;</button>'+
          '<button class="ok">&#10003;</button>'+
          '</div>');
$.imageResizer=function(){
    if(Uint8Array&&HTMLCanvasElement&&atob&&Blob){
        
    }else{
        return false;
    }
    var resizer=tmp.clone();
    
    resizer.image=resizer.find('img')[0];
    resizer.frames=resizer.find('.frames');
    resizer.okButton=resizer.find('button.ok');
    resizer.frames.offset={
        top:0,
        left:0
    };
    
    resizer.okButton.click(function(){
        resizer.clipImage();
    });
    resizer.clipImage=function(){
        var nh=this.image.naturalHeight,
            nw=this.image.naturalWidth,
            size=nw>nh?nh:nw;
        
        size=size>1000?1000:size;
        
        var canvas=$('<canvas width="'+size+'" height="'+size+'"></canvas>')[0],
            ctx=canvas.getContext('2d'),
            scale=nw/this.offset.width,
            x=this.frames.offset.left*scale,
            y=this.frames.offset.top*scale,
            w=this.frames.offset.size*scale,
            h=this.frames.offset.size*scale;
        
        ctx.drawImage(this.image,x,y,w,h,0,0,size,size);
        var src=canvas.toDataURL();
        this.canvas=canvas;
        this.append(canvas);
        this.addClass('uploading');
        this.removeClass('have-img');
        
        src=src.split(',')[1];
        if(!src)return this.doneCallback(null);
        src=window.atob(src);
        
        var ia = new Uint8Array(src.length);
        for (var i = 0; i < src.length; i++) {
            ia[i] = src.charCodeAt(i);
        };
        
        this.doneCallback(new Blob([ia], {type:"image/png"}));
    };
    
    resizer.resize=function(file,done){
        this.reset();
        this.doneCallback=done;
        this.setFrameSize(0);
        this.frames.css({
            top:0,
            left:0
        });
        var reader=new FileReader();
        reader.onload=function(){
            resizer.image.src=reader.result;
            reader=null;
            resizer.addClass('have-img');
            resizer.setFrames();
        };
        reader.readAsDataURL(file);
    };
    
    resizer.reset=function(){
        this.image.src='';
        this.removeClass('have-img');
        this.removeClass('uploading');
        this.find('canvas').detach();
    };
    
    resizer.setFrameSize=function(size){
        this.frames.offset.size=size;
        return this.frames.css({
            width:size+'px',
            height:size+'px'
        });
    };
    
    resizer.getDefaultSize=function(){
        var width=this.find(".inner").width(),
            height=this.find(".inner").height();
        this.offset={
            width:width,
            height:height
        };
        console.log(this.offset)
        return width>height?height:width;
    };
    
    resizer.moveFrames=function(offset){
        var x=offset.x,
            y=offset.y,
            top=this.frames.offset.top,
            left=this.frames.offset.left,
            size=this.frames.offset.size,
            width=this.offset.width,
            height=this.offset.height;
        
        if(x+size+left>width){
            x=width-size;
        }else{
            x=x+left;
        };
        
        if(y+size+top>height){
            y=height-size;
        }else{
            y=y+top;
        };
        x=x<0?0:x;
        y=y<0?0:y;
        this.frames.css({
            top:y+'px',
            left:x+'px'
        });
        
        this.frames.offset.top=y;
        this.frames.offset.left=x;
    };
    (function(){
        var time;
        function setFrames(){
            var size=resizer.getDefaultSize();
            resizer.setFrameSize(size);
        };
        
        window.onresize=function(){
            clearTimeout(time)
            time=setTimeout(function(){
                setFrames();
            },1000);
        };
        
        resizer.setFrames=setFrames;
    })();
    
    (function(){
        var lastPoint=null;
        function getOffset(event){
            event=event.originalEvent;
            var x,y;
            if(event.touches){
                var touch=event.touches[0];
                x=touch.clientX;
                y=touch.clientY;
            }else{
                x=event.clientX;
                y=event.clientY;
            }
            
            if(!lastPoint){
                lastPoint={
                    x:x,
                    y:y
                };
            };
            
            var offset={
                x:x-lastPoint.x,
                y:y-lastPoint.y
            }
            lastPoint={
                x:x,
                y:y
            };
            return offset;
        };
        resizer.frames.on('touchstart mousedown',function(event){
            getOffset(event);
        });
        resizer.frames.on('touchmove mousemove',function(event){
            if(!lastPoint)return;
            var offset=getOffset(event);
            resizer.moveFrames(offset);
        });
        resizer.frames.on('touchend mouseup',function(event){
            lastPoint=null;
        });
    })();
    return resizer;
};
var resizer=$.imageResizer(),
    resizedImage;

if(!resizer){
    resizer=$("<p>Your browser doesn't support these feature:</p><ul><li>canvas</li><li>Blob</li><li>Uint8Array</li><li>FormData</li><li>atob</li></ul>")   
};

$('.container').append(resizer);

$('input').change(function(event){
    var file=this.files[0];
    resizer.resize(file,function(file){
        resizedImage=file;
    });
});

$('button.submit').click(function(){
    var url=$('input.url').val();
    if(!url||!resizedFile)return;
    var fd=new FormData();
    fd.append('file',resizedFile);
    $.ajax({
        type:'POST',
        url:url,
        data:fd
    });
});