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  • Canvas绘画之旅

    定义在浏览器的画布
             1：不建议直接设置宽高，因为这是画布的大小，还有分辨率的大小（实际尺寸和分辨率）

    2：可以再js里面设置大小
     
    3：当用户的浏览器不支持canvas时显示
     4：不显示内容用js   if-else  语句写

     5：getContext() 方法返回一个用于在画布上绘图的环境。
    语法
    Canvas.getContext(contextID)
    参数
    参数 contextID 指定了您想要在画布上绘制的类型。当前唯一的合法值是 "2d"，它指定了二维绘图，并且导致这个方法返回一个环境对象，该对象导出一个二维绘图 API。
    6：画直线
     moveTO笔尖位置——lineTO从100-700的线_—stroke() 绘制
    以画布左上角为原点 x y轴展开
    //设置线条宽度
            context.lineWidth = 5; 
    //线条样式(大多颜色)
            context.strokeStyle = "#005588";
    想接着画 就在 lineTO后接着写 绘制第二条线条 
    //接着绘制线条，出现第二个
                context.lineTo(100, 700);
                context.lineTo(100, 100); 

    stroke()   绘制线条！！！
     7：//fillStyle 着色 填充
                context.fillStyle = "rgb(2,100,30)"
                //实心绘制
                context.fill()
    8：
     出现都是黑色线条  因为canvasmoveTo+lineTo是绘制状态不是确定
    想分开：
    beginPath(); ------------closePath();
    beginPath方法类似于开启新的路径绘画或清空已有路径
    而closePath并不是用来表示结束 而是功能性的 做图形闭合处理
    -----------------------------------【绘制七巧板】------------------------------

    <canvas id="canvas" width="800" height="600" style="border:1px solid #aaa;display: block; margin: 50px auto;">
                当前浏览器不支持。
            </canvas>
            <script type="text/javascript">
            //数组   七块
                var  tangram = [
                {p:[{x:0,y:0},{x:800,y:0},{x:400,y:400}],color:"#caff67"},
                {p:[{x:0,y:0},{x:400,y:400},{x:0,y:800}],color:"#67becf"},
                {p:[{x:800,y:0},{x:800,y:400},{x:600,y:600},{x:600,y:200}],color:"#ef3d61"},
                {p:[{x:600,y:200},{x:600,y:600},{x:400,y:400}],color:"#f9f51a"},
                {p:[{x:400,y:400},{x:600,y:600},{x:400,y:800},{x:200,y:600}],color:"#a594c0"},
                {p:[{x:200,y:600},{x:400,y:800},{x:0,y:800}],color:"#fa8ecc"},
                {p:[{x:800,y:400},{x:800,y:800},{x:400,y:800}],color:"#f6ca29"}        
                ];
                window.onload = function(){
                    var canvas =document.getElementById("canvas");
                    
                    canvas.width = 800;
                    canvas.height = 800;
                    
                    var context = canvas.getContext("2d");
                    for (var i = 0; i<tangram.length;i++) {
                        //那一块+绘图环境
                        draw(tangram[i],context);                    
                    }
                }
                function draw(piece,cxt){
                    cxt.beginPath();
                    cxt.moveTo(piece.p[0].x,piece.p[0].y);
                    for (var i =1;i<piece.p.lenth;i++) {
                        cxt.lineTo(pece.p[i].x,piece.p[i].y);}
                        cxt.closePath();
                        //填充颜色
                        cxt.fillStyle = piece.color;
                        cxt.fill();
                        //外邊框
                        cxt.strokeStyle = 'black';
                        cxt.lineWidth = 3;
                        cxt.stroke();
                    
                }
            </script>  
    ----------------------------【结束】------------------------------------------------
    10：弧线
    从哪个弧度开始 -----结束-------=-false  顺时针方向绘制
     0的位置在右中间  
     11：绘制多段弧
     
     12：fillStyle填充颜色

     
     -----------------------------------【倒计时】-------------------------------------
    1：点阵式
     （1）：实心圆 （0）：空白
    2：有小边框
     
     
    CenterX=初始的x+第几列j * (包围盒的边长)2*（R+1) +（R+1）
    格子系统
    3：动画
     1：匿名函数（每一帧要做什么）2：时间（毫秒 隔多久执行）
    1：当期画面-数据调整
    4：clearRect（）对图像进行一次刷新
    -----------------------【程序】-----------------
    HTML
    <body style="height:100%">
        <canvas id="canvas" style="height:100%">
            当前浏览器不支持Canvas，请更换浏览器后再试
        </canvas>
        <script src="digit.js"></script>
        <script src="countdown.js"></script>
    </body>
    didit.js
    digit =
        [
            [
                [0,0,1,1,1,0,0],
                [0,1,1,0,1,1,0],
                [1,1,0,0,0,1,1],
                [1,1,0,0,0,1,1],
                [1,1,0,0,0,1,1],
                [1,1,0,0,0,1,1],
                [1,1,0,0,0,1,1],
                [1,1,0,0,0,1,1],
                [0,1,1,0,1,1,0],
                [0,0,1,1,1,0,0]
            ],//0
            [
                [0,0,0,1,1,0,0],
                [0,1,1,1,1,0,0],
                [0,0,0,1,1,0,0],
                [0,0,0,1,1,0,0],
                [0,0,0,1,1,0,0],
                [0,0,0,1,1,0,0],
                [0,0,0,1,1,0,0],
                [0,0,0,1,1,0,0],
                [0,0,0,1,1,0,0],
                [1,1,1,1,1,1,1]
            ],//1
            [
                [0,1,1,1,1,1,0],
                [1,1,0,0,0,1,1],
                [0,0,0,0,0,1,1],
                [0,0,0,0,1,1,0],
                [0,0,0,1,1,0,0],
                [0,0,1,1,0,0,0],
                [0,1,1,0,0,0,0],
                [1,1,0,0,0,0,0],
                [1,1,0,0,0,1,1],
                [1,1,1,1,1,1,1]
            ],//2
            [
                [1,1,1,1,1,1,1],
                [0,0,0,0,0,1,1],
                [0,0,0,0,1,1,0],
                [0,0,0,1,1,0,0],
                [0,0,1,1,1,0,0],
                [0,0,0,0,1,1,0],
                [0,0,0,0,0,1,1],
                [0,0,0,0,0,1,1],
                [1,1,0,0,0,1,1],
                [0,1,1,1,1,1,0]
            ],//3
            [
                [0,0,0,0,1,1,0],
                [0,0,0,1,1,1,0],
                [0,0,1,1,1,1,0],
                [0,1,1,0,1,1,0],
                [1,1,0,0,1,1,0],
                [1,1,1,1,1,1,1],
                [0,0,0,0,1,1,0],
                [0,0,0,0,1,1,0],
                [0,0,0,0,1,1,0],
                [0,0,0,1,1,1,1]
            ],//4
            [
                [1,1,1,1,1,1,1],
                [1,1,0,0,0,0,0],
                [1,1,0,0,0,0,0],
                [1,1,1,1,1,1,0],
                [0,0,0,0,0,1,1],
                [0,0,0,0,0,1,1],
                [0,0,0,0,0,1,1],
                [0,0,0,0,0,1,1],
                [1,1,0,0,0,1,1],
                [0,1,1,1,1,1,0]
            ],//5
            [
                [0,0,0,0,1,1,0],
                [0,0,1,1,0,0,0],
                [0,1,1,0,0,0,0],
                [1,1,0,0,0,0,0],
                [1,1,0,1,1,1,0],
                [1,1,0,0,0,1,1],
                [1,1,0,0,0,1,1],
                [1,1,0,0,0,1,1],
                [1,1,0,0,0,1,1],
                [0,1,1,1,1,1,0]
            ],//6
            [
                [1,1,1,1,1,1,1],
                [1,1,0,0,0,1,1],
                [0,0,0,0,1,1,0],
                [0,0,0,0,1,1,0],
                [0,0,0,1,1,0,0],
                [0,0,0,1,1,0,0],
                [0,0,1,1,0,0,0],
                [0,0,1,1,0,0,0],
                [0,0,1,1,0,0,0],
                [0,0,1,1,0,0,0]
            ],//7
            [
                [0,1,1,1,1,1,0],
                [1,1,0,0,0,1,1],
                [1,1,0,0,0,1,1],
                [1,1,0,0,0,1,1],
                [0,1,1,1,1,1,0],
                [1,1,0,0,0,1,1],
                [1,1,0,0,0,1,1],
                [1,1,0,0,0,1,1],
                [1,1,0,0,0,1,1],
                [0,1,1,1,1,1,0]
            ],//8
            [
                [0,1,1,1,1,1,0],
                [1,1,0,0,0,1,1],
                [1,1,0,0,0,1,1],
                [1,1,0,0,0,1,1],
                [0,1,1,1,0,1,1],
                [0,0,0,0,0,1,1],
                [0,0,0,0,0,1,1],
                [0,0,0,0,1,1,0],
                [0,0,0,1,1,0,0],
                [0,1,1,0,0,0,0]
            ],//9
            [
                [0,0,0,0],
                [0,0,0,0],
                [0,1,1,0],
                [0,1,1,0],
                [0,0,0,0],
                [0,0,0,0],
                [0,1,1,0],
                [0,1,1,0],
                [0,0,0,0],
                [0,0,0,0]
            ]//:
        ];  
    countdown.js
    var WINDOW_WIDTH = 1024;
    var WINDOW_HEIGHT = 768;
    var RADIUS = 8;
    var MARGIN_TOP = 60;
    var MARGIN_LEFT = 30;
    const endTime = new Date(2016,9,27,18,47,52);
    var curShowTimeSeconds = 0
    var balls = [];
    const colors = ["#33B5E5","#0099CC","#AA66CC","#9933CC","#99CC00","#669900","#FFBB33","#FF8800","#FF4444","#CC0000"]
    window.onload = function(){
        // WINDOW_WIDTH = document.body.clientWidth
        // WINDOW_HEIGHT = document.body.clientHeight
        // MARGIN_LEFT = Math.round(WINDOW_WIDTH /10);
        // RADIUS = Math.round(WINDOW_WIDTH * 4 / 5 / 108)-1
        // MARGIN_TOP = Math.round(WINDOW_HEIGHT /5);
        var canvas = document.getElementById('canvas');
        var context = canvas.getContext("2d");
        canvas.width = WINDOW_WIDTH;
        canvas.height = WINDOW_HEIGHT;
        curShowTimeSeconds = getCurrentShowTimeSeconds()
        setInterval(
            function(){
                render( context );
                update();
            }
            ,
            50
        );
    }
    function getCurrentShowTimeSeconds() {
        var curTime = new Date();
        var ret = endTime.getTime() - curTime.getTime();
        ret = Math.round( ret/1000 )
        return ret >= 0 ? ret : 0;
    }
    function update(){
        var nextShowTimeSeconds = getCurrentShowTimeSeconds();
        var nextHours = parseInt( nextShowTimeSeconds / 3600);
        var nextMinutes = parseInt( (nextShowTimeSeconds - nextHours * 3600)/60 )
        var nextSeconds = nextShowTimeSeconds % 60
        var curHours = parseInt( curShowTimeSeconds / 3600);
        var curMinutes = parseInt( (curShowTimeSeconds - curHours * 3600)/60 )
        var curSeconds = curShowTimeSeconds % 60
        if( nextSeconds != curSeconds ){
            if( parseInt(curHours/10) != parseInt(nextHours/10) ){
                addBalls( MARGIN_LEFT + 0 , MARGIN_TOP , parseInt(curHours/10) );
            }
            if( parseInt(curHours%10) != parseInt(nextHours%10) ){
                addBalls( MARGIN_LEFT + 15*(RADIUS+1) , MARGIN_TOP , parseInt(curHours/10) );
            }
            if( parseInt(curMinutes/10) != parseInt(nextMinutes/10) ){
                addBalls( MARGIN_LEFT + 39*(RADIUS+1) , MARGIN_TOP , parseInt(curMinutes/10) );
            }
            if( parseInt(curMinutes%10) != parseInt(nextMinutes%10) ){
                addBalls( MARGIN_LEFT + 54*(RADIUS+1) , MARGIN_TOP , parseInt(curMinutes%10) );
            }
            if( parseInt(curSeconds/10) != parseInt(nextSeconds/10) ){
                addBalls( MARGIN_LEFT + 78*(RADIUS+1) , MARGIN_TOP , parseInt(curSeconds/10) );
            }
            if( parseInt(curSeconds%10) != parseInt(nextSeconds%10) ){
                addBalls( MARGIN_LEFT + 93*(RADIUS+1) , MARGIN_TOP , parseInt(nextSeconds%10) );
            }
            curShowTimeSeconds = nextShowTimeSeconds;
        }
        updateBalls();
        console.log( balls.length)
    }
    function updateBalls(){
        for( var i = 0 ; i < balls.length ; i ++ ){
            balls[i].x += balls[i].vx;
            balls[i].y += balls[i].vy;
            balls[i].vy += balls[i].g;
            if( balls[i].y >= WINDOW_HEIGHT-RADIUS ){
                balls[i].y = WINDOW_HEIGHT-RADIUS;
                balls[i].vy = - balls[i].vy*0.75;
            }
        }
        var cnt = 0
        for( var i = 0 ; i < balls.length ; i ++ )
            if( balls[i].x + RADIUS > 0 && balls[i].x -RADIUS < WINDOW_WIDTH )
                balls[cnt++] = balls[i]
        while( balls.length > cnt ){
            balls.pop();
        }
    }
    function addBalls( x , y , num ){
        for( var i = 0  ; i < digit[num].length ; i ++ )
            for( var j = 0  ; j < digit[num][i].length ; j ++ )
                if( digit[num][i][j] == 1 ){
                    var aBall = {
                        x:x+j*2*(RADIUS+1)+(RADIUS+1),
                        y:y+i*2*(RADIUS+1)+(RADIUS+1),
                        g:1.5+Math.random(),
                        vx:Math.pow( -1 , Math.ceil( Math.random()*1000 ) ) * 4,
                        vy:-5,
                        color: colors[ Math.floor( Math.random()*colors.length ) ]
                    }
                    balls.push( aBall )
                }
    }
    function render( cxt ){
        cxt.clearRect(0,0,WINDOW_WIDTH, WINDOW_HEIGHT);
        var hours = parseInt( curShowTimeSeconds / 3600);
        var minutes = parseInt( (curShowTimeSeconds - hours * 3600)/60 )
        var seconds = curShowTimeSeconds % 60
        renderDigit( MARGIN_LEFT , MARGIN_TOP , parseInt(hours/10) , cxt )
        renderDigit( MARGIN_LEFT + 15*(RADIUS+1) , MARGIN_TOP , parseInt(hours%10) , cxt )
        renderDigit( MARGIN_LEFT + 30*(RADIUS + 1) , MARGIN_TOP , 10 , cxt )
        renderDigit( MARGIN_LEFT + 39*(RADIUS+1) , MARGIN_TOP , parseInt(minutes/10) , cxt);
        renderDigit( MARGIN_LEFT + 54*(RADIUS+1) , MARGIN_TOP , parseInt(minutes%10) , cxt);
        renderDigit( MARGIN_LEFT + 69*(RADIUS+1) , MARGIN_TOP , 10 , cxt);
        renderDigit( MARGIN_LEFT + 78*(RADIUS+1) , MARGIN_TOP , parseInt(seconds/10) , cxt);
        renderDigit( MARGIN_LEFT + 93*(RADIUS+1) , MARGIN_TOP , parseInt(seconds%10) , cxt);
        for( var i = 0 ; i < balls.length ; i ++ ){
            cxt.fillStyle=balls[i].color;
            cxt.beginPath();
            cxt.arc( balls[i].x , balls[i].y , RADIUS , 0 , 2*Math.PI , true );
            cxt.closePath();
            cxt.fill();
        }
    }
    function renderDigit( x , y , num , cxt ){
        cxt.fillStyle = "rgb(0,102,153)";
        for( var i = 0 ; i < digit[num].length ; i ++ )
            for(var j = 0 ; j < digit[num][i].length ; j ++ )
                if( digit[num][i][j] == 1 ){
                    cxt.beginPath();
                    cxt.arc( x+j*2*(RADIUS+1)+(RADIUS+1) , y+i*2*(RADIUS+1)+(RADIUS+1) , RADIUS , 0 , 2*Math.PI )
                    cxt.closePath()
                    cxt.fill()
                }
    }
    倒计时效果图
     时间管理效果图
    1：删除
    const endTime = new Date(2016,9,27,18,47,52);
    var curShowTimeSeconds = 0 
    2： 时间获取
    function getCurrentShowTimeSeconds() {
        var curTime = new Date();
        var ret = curTime.getHours()*3600+curTime.getMinutes()*60+curTime.getSeconds();
        return ret ;
    } 
     
     
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  • 原文地址：https://www.cnblogs.com/liuruimiku/p/6000908.html
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