<!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> window.onload = function(){ var canvas = document.getElementById(‘canvas‘); canvas.width = 1024; canvas.height = 768; if(canvas.getContext(‘2d‘)){ var context = canvas.getContext(‘2d‘); context.fillStyle = "blue"; context.fillRect(100,200,400,400); context.globalCompositeOperation = "sourse-over"; context.fillStyle = "red"; context.beginPath(); context.moveTo(400,300); context.lineTo(650,700); context.lineTo(150,700); context.closePath(); context.fill(); }else{ alert(‘当前游览器不支持Canvas，请更换游览器后再试！‘); } } </script> </body> <script> /*global globalAlpha globalCompositeOperation = "source-over"(default) sourse-atop sourse-in sourse-out destination-over //前面绘制的覆盖了后面绘制的图形 destination-atop destination-in destination-out lighter copy xor */ </script> </html>
canvas-7globleCompositeOperation.html
原文：http://www.cnblogs.com/cynthia-wuqian/p/4988524.html