源码：<!DOCTYPE html>，接下来我们就来聊聊关于html5绘制梯形代码?以下内容大家不妨参考一二希望能帮到您!
html5绘制梯形代码
源码：
<!DOCTYPE html>
<html>
<head>
<meta charset=”gbk”>
<title>中国标准国旗</title>
</head>
<body>
<canvas id=”canvas” width=”600″ height=”400″></canvas>
<script>
/**
使用HTML5绘制标准五星红旗
*/
var canvas = document.getElementById(“canvas”);
var context = canvas.getContext(‘2d’);
var width=canvas.width;
var height=width*2/3;
var w=width/30;//小网格的宽
context.fillStyle=”red”;
context.fillRect(0,0,width,height);
var maxR = 0.15, minR = 0.05;//
var maxX = 0.25, maxY = 0.25;//大五星的位置
var minX = [0.50, 0.60, 0.60, 0.50];
var minY = [0.10, 0.20, 0.35, 0.45];
// 画大☆
var ox = height * maxX, oy = height * maxY;
create5star(context,ox,oy,height * maxR,”#ff0″,0);//绘制五角星
// 画小★
for (var idx = 0; idx < 4; idx ) {
var sx = minX[idx] * height, sy = minY[idx] * height;
var theta = Math.atan((oy – sy)/(ox – sx));
create5star(context,sx, sy, height * minR, “#ff0”,-Math.PI/2 theta);
}
//辅助线
context.moveTo(0,height/2)
context.lineTo(width,height/2);
context.stroke();
context.moveTo(width/2,0);
context.lineTo(width/2,height);
context.stroke();
//画网格，竖线
for(var j=0;j< 15;j ){
context.moveTo(j*w,0);
context.lineTo(j*w,height/2);
context.stroke();
}
//画网格，横线
for(var j=0;j< 10;j ){
context.moveTo(0,j*w);
context.lineTo(width/2,j*w);
context.stroke();
}
//画大圆
context.beginPath();
context.arc(ox,oy,maxR*height,0,Math.PI*2,false);
context.closePath();
context.stroke();
// 画小圆
for (var idx = 0; idx < 4; idx ) {
context.beginPath();
var sx = minX[idx] * height, sy = minY[idx] * height;
context.arc(sx, sy, height * minR,0,Math.PI*2,false);
context.closePath();
context.stroke();
}
//大圆中心与小圆中心连接线
for (var idx = 0; idx < 4; idx ) {
context.moveTo(ox,oy);
var sx = minX[idx] * height, sy = minY[idx] * height;
context.lineTo(sx, sy);
context.stroke();
}
//绘制五角星
/**
* 创建一个五角星形状. 该五角星的中心坐标为(sx,sy),中心到顶点的距离为radius,rotate=0时一个顶点在对称轴上
* rotate:绕对称轴旋转rotate弧度
*/
function create5star(context,sx,sy,radius,color,rotato){
context.save();
context.fillStyle=color;
context.translate(sx,sy);//移动坐标原点
context.rotate(Math.PI rotato);//旋转
context.beginPath();//创建路径
var x = Math.sin(0);
var y= Math.cos(0);
var dig = Math.PI/5 *4;
for(var i = 0;i< 5;i ){//画五角星的五条边
var x = Math.sin(i*dig);
