canvas自由拼图

    

        

            

                
            
        
    
    

        
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#main_canvas是主要的工作区域

.middleware_img是若干,读取从外面选中的若干图片数据，将数据以Base64编码，依次写入的src属性。这些后面将会被当作参数，传给canvas

#canvas_middleware是代理。读取的数据由#canvas_middleware调用toDataURL()方法编码成Base64形式

#puzzle_bg和.middleware_img作用差不多，只不过这里是将背景图片的src传给它。它会将背景图片数据传给canvas

    var img_upload_instance=new img_upload({
        add_btn:"puzzle_add",
        onSelect:onSelect//读取图片回调
    });

define("html5_imgupload",["avalon-min"], function(avalon){
    var html5_img_upload=function(options){
        this.init(options);
    }
    html5_img_upload.prototype = {
        init : function(options) {
            //如果有自定义属性，覆盖默认属性
            avalon.mix(html5_img_upload.prototype,options);
            this.init_events();
        },
        init_events : function() {
            var _this=this;
            avalon.bind($(this.add_btn),"change",function(e) {
                _this.get_files(e);
            });
        },
        file_filter:[],
        ori_images:[],
        add_btn:null,
        upload_btn:null,
        max_upload_num:9,
        onSelect:function(file_filter){},
        _start:0,//已经读取图片数量
        filter:function(files) {
            var arrFiles=[];
            for (var i=0,file;file=files[i];i++){
                if(this._start+i
自定义图片选取回调

    

        
        
        ...
    

    function onSelect(file_filter){
        for(var i=this._start,len=file_filter.length;i200||img.height>200){//等比例缩放
                            var prop=Math.min(200/img.width,200/img.height);
                            img.width=img.width*prop;
                            img.height=img.height*prop;
                        }
                        //设置中转canvas尺寸
                        canvas_middleware.width=img.width;
                        canvas_middleware.height=img.height;
                        ctx.drawImage(img, 0, 0, img.width, img.height);
                        //将读取图片转换成base64,写入.middleware_list的src
                        html5_puzzle.middleware_list.push(canvas_middleware.
                        toDataURL("image/jpeg"));
                        if(!file_filter[i+1]){
                            //图片延迟加载到canvas,因为canvas有个读取过程，但是没有回调
                            var t = window.setTimeout(function() {
                                canvas_puzzle.init();
                                clearTimeout(t);
                            }, 1000);
                        }
                    };
                    img.src = dataURL;
                };
                delete reader;
            })(i);
            reader.readAsDataURL(file_filter[i]);//开始读取图片
        }
        this._start=0;
        img_upload_instance._destroy();
    }
canvas初始化
    var canvas = new canvasElement.Element();
    canvas.init("main_canvas", {
        width : canvas_w,
        height : canvas_h
    });
    Canvas.Element.prototype.init = function(el, oConfig) {
        if (el == "") {
            return;
        }
        this._initElement(el);
        this._initConfig(oConfig);
        this._createCanvasBackground();
        this._createContainer();
        this._initEvents();
        this._initCustomEvents();
    };
    Canvas.Element.prototype._initElement = function(el) {
        this._oElement = document.getElementById(el);
        this._oContextTop = this._oElement.getContext("2d");
    };
    Canvas.Element.prototype._initCustomEvents = function() {//设置自定义事件
        this.onRotateStart = new Canvas.CustomEvent("onRotateStart");
        this.onRotateMove = new Canvas.CustomEvent("onRotateMove");        
        this.onRotateComplete = new Canvas.CustomEvent("onRotateComplete");
        this.onDragStart = new Canvas.CustomEvent("onDragStart");    
        this.onDragMove = new Canvas.CustomEvent("onDragMove");
        this.onDragComplete = new Canvas.CustomEvent("onDragComplete");
    };
    Canvas.Element.prototype._initConfig = function(oConfig) {
        this._oConfig = oConfig;
        this._oElement.width = this._oConfig.width;
        this._oElement.height = this._oConfig.height;
        this._oElement.style.width = this._oConfig.width + "px";
        this._oElement.style.height = this._oConfig.height + "px";
    };
    Canvas.Element.prototype._initEvents = function() {
        var _this=this;
        avalon.bind(this._oElement,"mousedown",function(e){
             _this.onMouseDown(e);
        });
        avalon.bind(this._oElement,"mouseup",function(e){
             _this.onMouseUp(e);
        });
        avalon.bind(this._oElement,"mousemove",function(e){
            _this.onMouseMove(e);
        });
    };
    Canvas.Element.prototype._createContainer = function() {
        var canvasEl = document.createElement("canvas");
        canvasEl.id = this._oElement.id + "-canvas-container";
        ...
        this._oContextContainer = oContainer.getContext("2d"); 
    };
    Canvas.Element.prototype._createCanvasBackground = function() {
        var canvasEl = document.createElement("canvas");
        canvasEl.id = this._oElement.id + "-canvas-background";
        ...
        this._oContextBackground = oBackground.getContext("2d"); 
    };
可以看到初始化过程中多次创建


main_canvas-background-canvas绘制背景图片

main_canvas-container-canvas绘制除当前操作的图片外的其余图片

main_canvas绘制当前操作的图片


从上到下：main_canvas->main_canvas-container-canvas->main_canvas-background-canvas
canvas context:

main_canvas->_oContextTop

main_canvas-container-canvas->_oContextContainer

main_canvas-background-canvas->_oContextBackground


这下就看到canvas自由拼图的原理了，原来是3个canvas上下重叠起来，操作的时候对不同的canvas进行不同目标的绘制。

canvas绘制图片
接着图片选取完成后canvas_puzzle.init()
    var canvas_img=[];
    ...
    var canvas_puzzle= function() {
        return {
            init : function() {
                var img_list=document.querySelectorAll(".middleware_img");
                //第一张作为背景图片
                canvas_img[0]=new canvasImg.Img($("puzzle_bg"), {});
                avalon.each(img_list,function(i,el){
                    canvas_img.push(new canvasImg.Img(el, {}));
                    canvas.addImage(canvas_img[i+1]);
                });
                canvas.setCanvasBackground(canvas_img[0]);
                ...
            }
        };
    }();

canvasImg.Img是canvas对图片的封装.第一个参数是,前面提到的#puzzle_bg和.middleware_img就是作为第一个参数传入canvasImg.Img.第二个参数用来自定义图片的一些属性，比如边框宽度，4个角的大小等，如果定义的话会覆盖默认值。

canvasImg.Img封装图片后的效果

canvas.addImage(canvas_img[i+1])将canvas对除背景图片外的图片的封装绘制到canvas上


    Canvas.Element.prototype.addImage = function(oImg) {
        if(isEmptyObject(this._aImages))
            this._aImages = [];
        this._aImages.push(oImg);
        this.renderAll(false,true);
    };
_aImages是保存canvas图片封装的数组，renderAll()方法很重要，后面会说到。
canvas.setCanvasBackground(canvas_img[0])将背景图片绘制到canvas

    Canvas.Element.prototype.setCanvasBackground = function(oImg) {
        this._backgroundImg = oImg;
        var originalImgSize = oImg.getOriginalSize();
        this._oContextBackground.drawImage(oImg._oElement, 0, 0, originalImgSize.width, 
        originalImgSize.height);
    };
    Canvas.Img.prototype.getOriginalSize = function() {//获得canvas尺寸
        return { width: this._oElement.width, height: this._oElement.height }
    };
canvas事件操作
mousedown
    Canvas.Element.prototype.onMouseDown = function(e) {
        $("canvas_menu").style.display="none";
        var mp = this.findMousePosition(e);//鼠标相对位置
        if (this._currentTransform != null || this._aImages == null) {
            return;
        }
        var oImg = this.findTargetImage(mp, false);//获取目标图片
        //事件触发位置是不是在4个角上
        var action = (!this.findTargetCorner(mp, oImg)) ? "drag" : "rotate";
        if (action == "rotate") {
            this.onRotateMove.fire(e);//触发自定义事件
        } else if (action == "drag") {
            this.onDragMove.fire(e);
        }
        this._prevTransform=this._currentTransform = { 
            target: oImg,
            action: action,
            scalex: oImg.scalex,
            offsetX: mp.ex - oImg.left,
            offsetY: mp.ey - oImg.top,
            ex: mp.ex, ey: mp.ey,
            left: oImg.left, top: oImg.top,
            theta: oImg.theta 
        };
        //设置菜单位置
        $("canvas_menu").style.transform="rotate("+oImg.theta*180/3.14+"deg)";
        $("canvas_menu").style.left=oImg.left+"px";
        $("canvas_menu").style.top=oImg.top+"px";
        this.renderAll(false,false);
    };

this._prevTransform保存当前目标图片状态，替换图片时会用到这个变量

renderAll()方法是整个绘制的核心方法


Canvas.Element.prototype.renderAll=function(allOnTop,allowCorners) {
    var containerCanvas=allOnTop?this._oContextTop:this._oContextContainer;
    this._oContextTop.clearRect(0,0,parseInt(this._oConfig.width),parseInt(this._oConfig.height));
    containerCanvas.clearRect(0,0,parseInt(this._oConfig.width),parseInt(this._oConfig.height));
    if(allOnTop){//所有图片都要在最上面
        var originalImgSize=this._backgroundImg.getOriginalSize();
        //在最上层canvas绘制背景图片
        this._oContextTop.drawImage(this._backgroundImg._oElement, 0, 0,
        originalImgSize.width,originalImgSize.height);
    }
    for(var i=0,l=this._aImages.length-1;i
可以看到，如果allOnTop=false,从_aImages封装图片的数组的第一个元素到倒数第二个元素，会绘制到中间一层container-canvas,而_aImages数组的最后一个元素，即当前操作的图片，会绘制到最上面一层top-canvas，当然如果改变操作对象，_aImages数组也会相应的变化，保证当前操作的图片在_aImages数组的最后一个位置。
如果allOnTop=true,_aImages数组中的所有图片还有背景图片都会被绘制到最上面一层top-canvas.
设置allOnTop参数的目的在于上传时只有所有图片都在一个canvas context上，调用toDataURL()方法，就能获得整个拼图的base64字符串。
第二个参数allowCorners表示绘制时是否添加边框，边角。
前面将选中图片及背景图片绘制到canvas，最后this.renderAll(false,true)让边框，边角可见，是为了让用户知道图片可以进行操作。
    Canvas.Element.prototype.addImage = function(oImg) {
        ...
        this.renderAll(false,true);
    };
另外，无论怎么设置，renderAll()方法最终都会调用drawImageElement()方法进行实际意义上的绘制
Canvas.Element.prototype.drawImageElement = function(context,oImg,allowCorners) {
    if(oImg){
        oImg.cornervisibility=allowCorners;
        var offsetY = oImg.height / 2;
        var offsetX = oImg.width / 2;
        context.save();
        context.translate(oImg.left, oImg.top);
        context.rotate(oImg.theta);
        context.scale(oImg.scalex, oImg.scaley);
        this.drawBorder(context, oImg, offsetX, offsetY);
        var originalImgSize = oImg.getOriginalSize();
        var polaroidHeight =((oImg.height-originalImgSize.height)-(oImg.width-originalImgSize.width))/2;
        context.drawImage(oImg._oElement,-originalImgSize.width/2,(-originalImgSize.height)/2-polaroidHeight, 
        originalImgSize.width,originalImgSize.height);
        if (allowCorners)
            this.drawCorners(context, oImg, offsetX, offsetY);
        context.restore();
    }
};
mousemove
Canvas.Element.prototype.onMouseMove = function(e) {
    var mp = this.findMousePosition(e);
    if(this._aImages == null)
        return;
    if(this._currentTransform==null){
        var targetImg = this.findTargetImage(mp, true);
        this.setCursor(mp, targetImg);
    }
    else {
        if (this._currentTransform.action == "rotate") {
            this.rotateImage(mp);
            this.scaleImage(mp);
            this.onRotateMove.fire(e);
        }        
        else {
            this.translateImage(mp);
            this.onDragMove.fire(e);
        }
        this.renderTop();
    }        
};
里面的renderTop()方法只在最上层canvas绘制当前操作的图片
Canvas.Element.prototype.renderTop = function() {
    this._oContextTop.clearRect(0,0,parseInt(this._oConfig.width), parseInt(this._oConfig.height));
    this.drawImageElement(this._oContextTop, this._aImages[this._aImages.length-1],true);
};
mouseup
    Canvas.Element.prototype.onMouseUp = function(e) {
        if (this._aImages == null) {
            return;
        }
        var target=this._currentTransform.target;
        if (target)
            target.setImageCoords();//重置图片canvas封装
        if(this._currentTransform!= null&&this._currentTransform.action=="rotate") {
            this.onRotateComplete.fire(e);
        } else if (this._currentTransform!=null&&this._currentTransform.action == "drag"){
            this.onDragComplete.fire(e);
        }
        this._currentTransform = null;
        this.renderTop();
        if(this._aImages.length>0)//没有选中的图片
            $("canvas_menu").style.display="block";
    };
替换图片
    

        ...
        更改图片
    
    avalon.bind($("puzzle_update"),"click",function(){
        update_puzzle=true;
        $("puzzle_add_input").click();
    });
可以看到，这里依然使用了点击选中图片，不过设置了update_puzzle=true,表示当前处在替换图片的情况下
    function onSelect(file_filter){
        for(var i=this._start,len=file_filter.length;i
删除图片
    

        删除
        ...
    
    avalon.bind($("puzzle_delete"),"click",function(){
        canvas._aImages.splice(getCurImg(),1);//从_aImages数组中删除
        canvas.renderAll(false,false);//重新绘制
        $("canvas_menu").style.display="none";
        ...
    });
拼图转换成base64字符串
    Canvas.Element.prototype.canvasTo = function(format) {//canvas=>dataurl
        this.renderAll(true,false);//所有图片都绘制到最上层，并且不绘制边框，边角
        if (format == "jpeg" || format == "png") {
            return this._oElement.toDataURL("image/"+format);
        }
    };
上传
        avalon.post("...",{
            imgData:canvas.canvasTo("jpeg").substr(22)
        },function(data){
            ...
        },"json");
后台用Base64解析imgData字符串就可以了
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