HTML5 Canvas 绘制星条旗

更新时间：2022-09-16 21:56:48

HTML5 Canvas 绘制星条旗

代码：

<!DOCTYPE html>
<html lang="utf-8">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
<head>
     <title>美国国旗</title>
    </head>

     <body onload="draw()">
        <canvas id="myCanvus" width="380px" height="200px" style="border:1px dashed black;">
            出现文字表示你的浏览器不支持HTML5
        </canvas>
     </body>
</html>
<script type="text/javascript">
<!--
    function draw(){
        var canvas=document.getElementById("myCanvus");
        var canvasWidth=380;
        var canvasHeight=200;

        var context=canvas.getContext("2d");
        
        context.fillStyle = "white";
        context.fillRect(0, 0, canvasWidth, canvasHeight);
        
        var i;
        // 13个横条
        for(i=0;i<13;i++){
            if(i % 2==0){
                context.fillStyle = "red";
                context.fillRect(0, canvasHeight/13*i, canvasWidth, canvasHeight/13);
            }else{
                context.fillStyle = "white";
                context.fillRect(0, canvasHeight/13*i, canvasWidth, canvasHeight/13);
            }            
        }

        // 左上角蓝底
        var D=canvasWidth/5*2;
        var C=canvasHeight/13*7;
        context.fillStyle = "blue";
        context.fillRect(0, 0, D, C);

        // 画星星
        var x;
        var y;
        var j=0;

        context.strokeStyle = "white";
        context.fillStyle = "white"

        for(i=0;i<6;i++){
            for(j=0;j<5;j++){
                x=D/12+2*i*D/12;
                y=C/10+2*j*C/10;

                context.save();

                var r=5;
                context.translate(x-r,y-r);

                
                context.beginPath();
                context.moveTo(r, 0);
                context.lineTo(r+Math.cos(Math.PI*3/10)*r, r+Math.sin(Math.PI*3/10)*r);
                context.lineTo(r-Math.cos(Math.PI*1/10)*r, r-Math.sin(Math.PI*1/10)*r);
                context.lineTo(r+Math.cos(Math.PI*1/10)*r, r-Math.sin(Math.PI*1/10)*r);
                context.lineTo(r-Math.cos(Math.PI*3/10)*r, r+Math.sin(Math.PI*3/10)*r);
                context.lineTo(r, 0);
                context.fill();
                context.stroke();
                context.closePath();

                context.restore();
            }
        }

        for(i=0;i<5;i++){
            for(j=0;j<4;j++){
                x=D/6+2*i*D/12;
                y=C/5+2*j*C/10;

                context.save();

                var r=5;
                context.translate(x-r,y-r);

                
                context.beginPath();
                context.moveTo(r, 0);
                context.lineTo(r+Math.cos(Math.PI*3/10)*r, r+Math.sin(Math.PI*3/10)*r);
                context.lineTo(r-Math.cos(Math.PI*1/10)*r, r-Math.sin(Math.PI*1/10)*r);
                context.lineTo(r+Math.cos(Math.PI*1/10)*r, r-Math.sin(Math.PI*1/10)*r);
                context.lineTo(r-Math.cos(Math.PI*3/10)*r, r+Math.sin(Math.PI*3/10)*r);
                context.lineTo(r, 0);
                context.fill();
                context.stroke();
                context.closePath();

                context.restore();
            }
        }
    }

    function getRad(degree){
        return degree/180*Math.PI;
    }
//-->
</script>

关于美国国旗如何画请参考：https://wenku.baidu.com/view/d6eb1d40b4daa58da1114a32.html

本文转自张昺华-sky博客园博客，原文链接：http://www.cnblogs.com/xiandedanteng/p/7470362.html，如需转载请自行联系原作者

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HTML5 Canvas 绘制星条旗

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