HTML5中canvas元素用于图形的绘制，通过脚本 (通常是JavaScript)来完成.通过这一元素，我们可以在画布上画出各种图形，线条，矩形，圆形，椭圆，字体，渐变等，当然可以自己设计组合绘制自己想要的图案，今天，笔者通过canvas绘制了一个哆啦A梦的图案，其中，应用了颜色渐变，贝塞尔曲线等知识点，是对canvas的一个较综合的应用。请看效果图：
通过canvas画图需要确定各个点，比较繁琐，读者需要有耐心。请看代码：
<!DOCTYPE html><html><head><meta charset="UTF-8"><title></title><style type="text/css">*{margin: 0;padding: 0;}.box{width: 600px;height: 800px;border: 1px solid black;margin: 0 auto;}</style></head><body><div class="box"><canvas id="canvas" width="600px" height="800px"></canvas></div><script type="text/javascript">var canvas = document.getElementById("canvas");var ctx = canvas.getContext('2d');ctx.lineWidth = 4;/*画椭圆*/function ellipse(context, x, y, a, b) {context.save();var r = (a > b) ? a : b;var ratioX = a / r;var ratioY = b / r;context.scale(ratioX, ratioY);context.beginPath();context.arc(x / ratioX, y / ratioY, r, 0, 2 * Math.PI, false);context.closePath();context.restore();context.fillStyle = "black";if(a<=10){context.fillStyle = "white";}context.fill();}//头部外圈ctx.beginPath();ctx.arc(300,200,200,0.25*Math.PI,0.75*Math.PI,true);ctx.quadraticCurveTo(306, 403, 444, 340);var color = ctx.createRadialGradient(140,50,20,120,30,200);color.addColorStop(0.0,"white");color.addColorStop(1.0,"#019FE8");ctx.fillStyle = color;ctx.fill();ctx .stroke();ctx.closePath();//头部内圈ctx.beginPath();ctx.arc(300,230,175,0.25*Math.PI,0.75*Math.PI,true);ctx.quadraticCurveTo(306, 403, 424, 350);ctx.fillStyle = "white";ctx.fill();ctx.stroke();ctx.closePath();//左眼睛ctx.beginPath();ctx.moveTo(300, 50);ctx.arc(260,50,40,0,2*Math.PI);ctx.moveTo(256, 60);ctx.quadraticCurveTo(273, 25, 286, 60);ctx.fillStyle = "white";ctx.fill();ctx.stroke();ctx.closePath();//右眼睛ctx.beginPath();ctx.moveTo(380, 50);ctx.arc(340,50,40,0,2*Math.PI);ctx.fillStyle = "white";ctx.fill();ctx.stroke();ctx.closePath();//椭圆眼珠子ellipse(ctx, 326, 50, 14, 20);ellipse(ctx, 322, 46, 5, 7);//鼻子ctx.beginPath();ctx.moveTo(300, 125);ctx.arc(300,100,25,0.5*Math.PI,2.5*Math.PI);ctx.fillStyle = "#E70012";ctx.fill();ctx.lineTo(300,200);ctx.stroke();ctx.closePath();ellipse(ctx, 306, 96, 9, 9);//胡须ctx.beginPath();ctx.moveTo(260,125);ctx.lineTo(180,100);ctx.moveTo(260,150);ctx.lineTo(160,150);ctx.moveTo(260,175);ctx.lineTo(170,200);ctx.moveTo(340,125);ctx.lineTo(420,100);ctx.moveTo(340,150);ctx.lineTo(440,150);ctx.moveTo(340,175);ctx.lineTo(430,200);ctx.moveTo(173, 125);ctx.bezierCurveTo(96, 95, 88, 238, 200, 218);ctx.moveTo(422, 119);ctx.bezierCurveTo(501, 84, 517, 217, 402, 215);ctx.fillStyle = "white";ctx.fill();ctx.stroke();ctx.closePath();//嘴巴ctx.beginPath();ctx.moveTo(164, 218);ctx.quadraticCurveTo(298, 453, 434, 214);ctx.bezierCurveTo(414,218,340,192,300,200);ctx.bezierCurveTo(260,192,186,218,164, 218);ctx.fillStyle = "#E70012";ctx.fill();ctx.stroke();ctx.closePath();//舌头ctx.beginPath();ctx.moveTo(233, 308);ctx.bezierCurveTo(230, 271, 283, 268, 300, 284);ctx.bezierCurveTo(319, 271, 371, 264, 359, 310);ctx.quadraticCurveTo(298, 360, 233, 308);ctx.fillStyle = "#EC6D1E";ctx.fill();ctx.stroke();ctx.closePath();//左手ctx.beginPath();ctx.moveTo(100,400);ctx.arc(80,440,45,0,2*Math.PI);ctx.stroke();ctx.closePath();//身子ctx.beginPath();ctx.moveTo(150, 360);ctx.lineTo(100,400);ctx.quadraticCurveTo(90, 430, 120, 440);ctx.lineTo(150,430);ctx.lineTo(154,386);ctx.quadraticCurveTo(140, 500, 150, 560);ctx.quadraticCurveTo(136,580,140,600);ctx.quadraticCurveTo(200,610,270,600);ctx.arc(300,600,30,1*Math.PI,2*Math.PI);ctx.quadraticCurveTo(390,610,460,600);ctx.quadraticCurveTo(466,580,450,560);ctx.quadraticCurveTo(460,500,450,386);ctx.moveTo(452,420);ctx.lineTo(560,280);ctx.lineTo(520,250);ctx.lineTo(480,286);ctx.quadraticCurveTo(400,450,150, 360);ctx.fillStyle = "#019fe8";ctx.fill();ctx.stroke();ctx.closePath();//肚兜ctx.beginPath();ctx.moveTo(200,440);ctx.bezierCurveTo(170,580,440,570,400,440);ctx.bezierCurveTo(390,360,210,360,200,440);ctx.moveTo(220,460);ctx.bezierCurveTo(210,550,400,540,380,460);ctx.quadraticCurveTo(300,470,220,460);ctx.fillStyle = "white";ctx.fill();ctx.stroke();ctx.closePath();//脖子ctx.beginPath();ctx.moveTo(444, 340);ctx.quadraticCurveTo(306, 403, 156, 340);ctx.quadraticCurveTo(146, 340, 150, 360);ctx.quadraticCurveTo(306, 423, 450, 360);ctx.quadraticCurveTo(454, 340, 444, 340);ctx.fillStyle = "#E30115";ctx.fill();ctx.stroke();ctx.closePath();//铃铛ctx.beginPath();ctx.moveTo(334, 410);ctx.arc(300,410,34,0,2*Math.PI);ctx.strokeStyle = "black";ctx.fillStyle = "#FFD000";ctx.moveTo(265, 404);ctx.quadraticCurveTo(289, 395, 336, 404);ctx.moveTo(265, 412);ctx.quadraticCurveTo(289, 403, 336, 412);ctx.moveTo(300,444);ctx.lineTo(300,424);ctx.fill();ctx.stroke();ctx.closePath();ctx.beginPath();ctx.moveTo(305, 420);ctx.arc(300,420,5,0,2*Math.PI);ctx.strokeStyle = "black";ctx.fillStyle = "gray";ctx.fill();ctx.stroke();ctx.closePath();//右手ctx.beginPath();ctx.moveTo(595,250);ctx.arc(550,250,45,0,2*Math.PI);ctx.fillStyle = "white";ctx.fill();ctx.stroke();ctx.closePath();//左脚ctx.beginPath();ctx.moveTo(140,600);ctx.quadraticCurveTo(100,610,100,640);ctx.bezierCurveTo(100,700,300,680,290,640);ctx.quadraticCurveTo(290,610,270,600);ctx.stroke();ctx.closePath();//右脚ctx.beginPath();ctx.moveTo(330,600);ctx.quadraticCurveTo(310,610,310,640);ctx.bezierCurveTo(320,700,510,680,500,640);ctx.quadraticCurveTo(500,610,460,600);ctx.stroke();ctx.closePath();//字体ctx.beginPath();ctx.lineWidth = 2;ctx.font = "bold 40px 楷体";var fontColor = ctx.createLinearGradient(250,455,280,545);fontColor.addColorStop(0.0,"yellow");fontColor.addColorStop(1.0,"red");ctx.fillStyle = fontColor;ctx.fillText("梦",280,505,50);ctx.closePath();</script></body></html>
读者需要注意，通过canvas画图，填充颜色的时候后面的颜色会覆盖住前面的颜色，最简单的解决方法就是调整一下前后位置就可以。读者可以自行运行，查看效果。
