Apprendre en jouant avec HTML5 (6) - Introduction détaillée aux Autobots et aux transformations

代码



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--><canvas id="canvas1" width="250" height="300" 

    onmousedown="trans.transform(event);"  

    onmouseup="trans.init(event);" 

    onmousemove="trans.translate(event);" 

    style="background-color:black">

    你的浏览器不支持 &lt;canvas&gt;标签，请使用 Chrome 浏览器 或者 FireFox 浏览器

</canvas><br/>

<input type="radio" name="r" id="r1" checked="checked">移动——在图像上按住鼠标并移动<br />

<input type="radio" name="r" id="r2">基准点缩放——在图像某点处按住鼠标<br />

<input type="radio" name="r"  id="r3">基准点旋转——在图像某点处按住鼠标<br />

<input type="radio" name="r"  id="r4">基准点缩放同时旋转——在图像某点处按住鼠标<br />



<canvas id="canvas3" width="250" height="300" style="background-color:black">

    你的浏览器不支持 &lt;canvas&gt;标签，请使用 Chrome 浏览器 或者 FireFox 浏览器

</canvas><br/>

<input type="button" onclick="move(1);" value="移动裁剪区域">

<input type="button" onclick="move(2);" value="移动蒙版">

<input type="button" onclick="stop();" value="停止移动"><br />



        <div>

            <table>

                <tr>

                    <td><canvas id="tut0" width="125" height="125"></canvas><br/><label id="lab0"></label></td>

                <td><canvas id="tut1" width="125" height="125"></canvas><br/><label id="lab1"></label></td>

                <td><canvas id="tut2" width="125" height="125"></canvas><br/><label id="lab2"></label></td>

                <td><canvas id="tut3" width="125" height="125"></canvas><br/><label id="lab3"></label></td>

                </tr>

                <tr>

                    <td><canvas id="tut4" width="125" height="125"></canvas><br/><label id="lab4"></label></td>

                <td><canvas id="tut5" width="125" height="125"></canvas><br/><label id="lab5"></label></td>

                <td><canvas id="tut6" width="125" height="125"></canvas><br/><label id="lab6"></label></td>

                <td><canvas id="tut7" width="125" height="125"></canvas><br/><label id="lab7"></label></td>

                </tr>

                <tr>

                    <td><canvas id="tut8" width="125" height="125"></canvas><br/><label id="lab8"></label></td>

                <td><canvas id="tut9" width="125" height="125"></canvas><br/><label id="lab9"></label></td>

                <td><canvas id="tut10" width="125" height="125"></canvas><br/><label id="lab10"></label></td>

                <td><canvas id="tut11" width="125" height="125"></canvas><br/><label id="lab11"></label></td>

                </tr>

            </table>

        </div>





<script type="text/javascript">

    //美女图的 Base64 编码

    IMG_SRC=&#39;data:image/gif;base64,/9j/4QDfRXhpZgAASUkqAAgAAAAFABIBAwA......&#39;;//省略四十字节



    //==========================================

    //基准点变形类

    //==========================================

    function Transform(){

        //获取画布对象

        this.ctx = document.getElementById("canvas1").getContext("2d");

        //创建图像对象

        this.img=new Image();

        //指定图像源

        this.img.src=IMG_SRC;

        this.interval = null;

        //鼠标按钮状态

        this.pressed=false;

        this.init();

    }

    

    //初始化图形

    Transform.prototype.init=function(){

        //鼠标按钮状态

        this.pressed=false;

        //停止计时器

        if(this.interval) clearInterval(this.interval);

        //变化值

        this.delta = 0.06;

        //清空

        this.ctx.clearRect(0,0,250,300);

        //重绘

        this.paint();

    }

    

    //绘制图像

    Transform.prototype.paint=function(){

        var that=this;

        var img=this.img

        if(img.complete)

            that.ctx.drawImage(img,0,0);

        else 

            var interval = setInterval(function(){

                if(img.complete){

                    that.ctx.drawImage(img,0,0);

                    clearInterval(interval);

                }

            },300);

    }

    

    //鼠标按钮按下后，开始变形

    Transform.prototype.transform = function(){

        //获取基准点

        this.dx=event.offsetX;

        this.dy=event.offsetY;

        //获取基准点

        this.startx=event.offsetX;

        this.starty=event.offsetY;

        //初始缩放比例

        this.sc=1;

        //初旋转角度

        this.angle=0;

        

        var that=this;

        if(document.getElementById("r1").checked)

            //鼠标按钮状态

            this.pressed=true;

        else if(document.getElementById("r2").checked)

            this.interval = setInterval(function(){that.scale()},50);

        else if((document.getElementById("r3").checked))

            this.interval = setInterval(function(){that.rotate()},50);

        else 

            this.interval = setInterval(function(){that.scaleAndRotate()},50);

    }

    

    //移动

    Transform.prototype.translate = function(){

        this.ddx=event.offsetX-this.startx;

        this.ddy=event.offsetY-this.starty;

        if(this.pressed){

            //清空

            this.ctx.clearRect(0,0,250,300);

            //保存状态

            this.ctx.save();

            //平移

            this.ctx.translate(this.ddx,this.ddy);

            //重绘

            this.paint();

            //绘制基准点

            this.ctx.fillStyle="red";

            this.ctx.fillRect(this.dx-5,this.dy-5,10,10);

            //恢复状态

            this.ctx.restore();

        }

    }



    //缩放变形

    Transform.prototype.scale = function(){

        //清空

        this.ctx.clearRect(0,0,250,300);

        //改变缩放比例

        this.sc=this.sc - this.delta;

        if(this.sc<0.2 || this.sc>2) 

            this.delta = -this.delta;

        //保存状态

        this.ctx.save();

        //以 (dx,dy) 为基准点进行 (sx,sy)比例缩放：transform(sx, 0, 0, sy, dx(1-sx), dy(1-sy))

        this.ctx.transform(this.sc, 0, 0, this.sc, this.dx*(1-this.sc), this.dy*(1-this.sc))

        //用新的变形矩阵重绘

        this.paint();

        //绘制基准点

        this.ctx.fillStyle="red";

        this.ctx.fillRect(this.dx-5,this.dy-5,10,10);

        //恢复状态

        this.ctx.restore();

    }

    

    //旋转变形

    Transform.prototype.rotate = function(){

        //清空

        this.ctx.clearRect(0,0,250,300);

        //改变缩放比例

        var PI = Math.PI;

        this.angle=this.angle + PI/60;

        //保存状态

        this.ctx.save();

        //以 (dx,dy) 为基准点旋转角度 A：transform(cosA, sinA, -sinA, cosA, dx(1-cosA) + dysinA, dy(1-cosA) - dxsinA)

        this.ctx.transform(Math.cos(this.angle), Math.sin(this.angle), 

                -Math.sin(this.angle), Math.cos(this.angle), 

                this.dx*(1-Math.cos(this.angle)) + this.dy*Math.sin(this.angle), 

                this.dy*(1-Math.cos(this.angle)) - this.dx*Math.sin(this.angle))

        //用新的变形矩阵重绘

        this.paint();

        //绘制基准点

        this.ctx.fillStyle="red";

        this.ctx.fillRect(this.dx-5,this.dy-5,10,10);

        //恢复状态

        this.ctx.restore();

    }

    

    //即缩放又旋转变形,没有使用变形矩阵

    Transform.prototype.scaleAndRotate = function(){

        //清空

        this.ctx.clearRect(0,0,250,300);

        //改变缩放比例

        this.sc=this.sc - this.delta;

        if(this.sc<0.2 || this.sc>2) 

            this.delta = -this.delta;

        var PI = Math.PI;

        this.angle=this.angle + PI/60;

        //保存状态

        this.ctx.save();

        //先移动原点到基点

        this.ctx.translate(this.dx,this.dy);

        this.ctx.scale(this.sc,this.sc);

        this.ctx.rotate(this.angle);

        this.ctx.translate(-this.dx,-this.dy);

        //用新的变形矩阵重绘

        this.paint();

        //绘制基准点

        this.ctx.fillStyle="red";

        this.ctx.fillRect(this.dx-5,this.dy-5,10,10);

        //恢复状态

        this.ctx.restore();

    }

    

    var trans = new Transform();

    

    //==========================================

    function Clip(){

        var canvas = document.getElementById("canvas3");

        this.ctx = canvas.getContext("2d");

        this.img=new Image();

        this.img.src=IMG_SRC;

        //移动方向

        this.delta=[3,3];

        //起始点

        this.pos_x = 225;

        this.pos_y = 120;

        //半径

        this.radius = 40;

        //画布的长和宽

        this.w = parseInt(canvas.getAttribute("width"));

        this.h = parseInt(canvas.getAttribute("height"));

    }

    

    Clip.prototype.draw1=function(){

        //碰撞检测

        if (this.pos_x < this.radius) {

            this.delta[0] = Math.random() % 4 + 5;

        } else if (this.pos_x > this.w - this.radius) {

            this.delta[0] = -(Math.random() % 4 + 5);

        }

        if (this.pos_y < this.radius) {

            this.delta[1] = Math.random() % 4 + 5;

        } else if (this.pos_y > this.h - this.radius) {

            this.delta[1] = -(Math.random() % 4 + 5);

        }

        this.pos_x += this.delta[0];

        this.pos_y += this.delta[1];



        this.ctx.clearRect(0, 0, this.w, this.h);

        //保存状态

        this.ctx.save()

        //移动变形

        this.ctx.translate(this.pos_x,this.pos_y);

        //设置裁剪区域

        this.ctx.beginPath();

        this.ctx.arc(0 ,0,this.radius,0,Math.PI*2,true);

        this.ctx.clip();         

        // 将图片画到画布上

        this.ctx.drawImage(this.img, -this.pos_x, -this.pos_y,this.w, this.h);

        //恢复状态

        this.ctx.restore();

    }

    

    Clip.prototype.draw2=function(){

        //碰撞检测

        if (this.pos_x < this.radius) {

            this.delta[0] = Math.random() % 4 + 5;

        } else if (this.pos_x > this.w - this.radius) {

            this.delta[0] = -(Math.random() % 4 + 5);

        }

        if (this.pos_y < this.radius) {

            this.delta[1] = Math.random() % 4 + 5;

        } else if (this.pos_y > this.h - this.radius) {

            this.delta[1] = -(Math.random() % 4 + 5);

        }

        this.pos_x += this.delta[0];

        this.pos_y += this.delta[1];



        this.ctx.clearRect(0, 0, this.w, this.h);

        //绘制灰色的半透明蒙版

        this.ctx.fillStyle="rgba(125,125,125,0.9)"

        this.ctx.fillRect(0, 0, this.w, this.h);

        //保存状态

        this.ctx.save()

        //移动坐标

        this.ctx.translate(this.pos_x,this.pos_y);

        //裁剪透明的圆形区域

        this.ctx.globalCompositeOperation = "xor";   

        this.ctx.fillStyle="white"

        this.ctx.beginPath();

        this.ctx.arc(0 ,0,this.radius,0,Math.PI*2,true);

        this.ctx.fill();       

        // 将图片画到蒙版的下面，即只露出透明区域

        this.ctx.globalCompositeOperation = "destination-over";   

        this.ctx.drawImage(this.img, -this.pos_x, -this.pos_y,this.w, this.h);

        //恢复状态

        this.ctx.restore();

    }



    var cl=new Clip();

    cl.interval=null;

    

    function move(id){      

        if(cl.interval)

            clearInterval(cl.interval)

        if(id==1){

            cl.ctx.clearRect(0, 0, 450, 300);    

            cl.interval=setInterval(function(){cl.draw1()},20);

        }

        else{

            cl.ctx.clearRect(0, 0, 450, 300);    

            cl.interval=setInterval(function(){cl.draw2()},20);

        }

    }



    function stop(){

        clearInterval(cl.interval)

    }

    

    var compositeTypes = [

        &#39;source-over&#39;,&#39;source-in&#39;,&#39;source-out&#39;,&#39;source-atop&#39;,

        &#39;destination-over&#39;,&#39;destination-in&#39;,&#39;destination-out&#39;,&#39;destination-atop&#39;,

        &#39;lighter&#39;,&#39;darker&#39;,&#39;copy&#39;,&#39;xor&#39;

    ];

    function drawComp(){

        for (i=0;i<compositeTypes.length;i++){

            var label = document.createTextNode(compositeTypes[i]);

            document.getElementById(&#39;lab&#39;+i).appendChild(label);

            var ctx = document.getElementById(&#39;tut&#39;+i).getContext(&#39;2d&#39;);



            // draw rectangle

            ctx.fillStyle = "#09f";

            ctx.fillRect(15,15,70,70);



            // set composite property

            ctx.globalCompositeOperation = compositeTypes[i];



            // draw circle

            ctx.fillStyle = "#f30";

            ctx.beginPath();

            ctx.arc(75,75,35,0,Math.PI*2,true);

            ctx.fill();

        }

    }

    drawComp();

</script>