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canvas-8searchLight3.html

时间:2015-11-23 16:47:13      阅读:139      评论:0      收藏:0      [点我收藏+]

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<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
</head>
<body>
    <canvas id="canvas" style="margin:0 auto;border:1px #ddd solid">
        The current browser does not support Canvas, can replace the browser a try!
    </canvas>

    <script>

        var searchLight = {
            x : 400,
            y : 400,
            radius : 150,
            vx : Math.random() * 5 + 10,
            vy : Math.random() * 5 + 10
        }

        var rot = 0;

        window.onload = function(){
            var canvas = document.getElementById(canvas);

            canvas.width = 1024;
            canvas.height = 768;

            if(canvas.getContext(2d)){
                var context = canvas.getContext(2d);

                setInterval(function(){    
                        draw(context);
                        update(canvas.width,canvas.height);
                },40);

            }else{
                alert(当前游览器不支持Canvas,请更换游览器后再试!);
            }
        }

        function draw(cxt){
            var canvas = cxt.canvas;
            cxt.clearRect(0,0,canvas.width,canvas.height);

            cxt.save();

                cxt.beginPath();
                    cxt.fillStyle = "#000";
                    cxt.fillRect(0,0,canvas.width,canvas.height)
                cxt.closePath();

                cxt.save();
                    cxt.translate(searchLight.x,searchLight.y);
                    cxt.rotate(rot/180*Math.PI);
                    cxt.scale(searchLight.radius,searchLight.radius);
                    starPath(cxt);
                    cxt.fillStyle = "#fff";
                    cxt.fill();
                cxt.restore();
                    cxt.clip();

                cxt.font = "bold 150px Arial";
                cxt.textAlign = "center";
                cxt.textBaseline = "middle";
                cxt.fillStyle = "#058";
                cxt.fillText("Canvas",canvas.width/2,canvas.height/4);
                cxt.fillText("Canvas",canvas.width/2,canvas.height/2);
                cxt.fillText("Canvas",canvas.width/2,canvas.height * 3/4);
            cxt.restore();
        }


        function starPath(cxt){
        
            cxt.beginPath();
            for(var i=0;i<5;i++){
                cxt.lineTo(Math.cos( (18+i*72) / 180 * Math.PI ),
                                -Math.sin( (18+i*72) / 180 * Math.PI ));
                cxt.lineTo(Math.cos( (54+i*72) / 180 * Math.PI )*0.5,
                                -Math.sin( (54+i*72) / 180 * Math.PI )*0.5);
            }
            cxt.closePath();
        }


        function update(canvasWidth,canvasHeight){
            rot += 1;

            searchLight.x += searchLight.vx;
            searchLight.y += searchLight.vy;

            if(searchLight.x - searchLight.radius <= 0){
                searchLight.vx = -searchLight.vx;
                searchLight.x = searchLight.radius;
            }

            if(searchLight.x + searchLight.radius >= canvasWidth){
                searchLight.vx = -searchLight.vx;
                searchLight.x = canvasWidth - searchLight.radius;
            }

            if(searchLight.y - searchLight.radius <= 0){
                searchLight.vy = -searchLight.vy;
                searchLight.y = searchLight.radius;
            }

            if(searchLight.y + searchLight.radius >= canvasHeight){
                searchLight.vy = -searchLight.vy;
                searchLight.y = canvasHeight - searchLight.radius;
            }
        }

    </script>
</body>
</html>

 

canvas-8searchLight3.html

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原文地址:http://www.cnblogs.com/cynthia-wuqian/p/4988532.html

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