HTML通过canvas导入图片

 /** * Created by chenyufeng on 15/9/27.
    
  */
    
 var CANVAS_WIDTH = 500, CANVAS_HEIGHT = 500;
    
 var mycanvas,context;
    
  
    
 window.onload = function(){
    
  
    
     createCanvas();
    
     drawImage();
    
  
    
 };
    
  
    
 function createCanvas(){
    
  
    
     document.body.innerHTML = "<canvas id=\"mycanvas\" width=\""+CANVAS_WIDTH+"\" height=\""+CANVAS_HEIGHT+"\"></canvas>";
    
  
    
     mycanvas = document.getElementById("mycanvas");
    
     context = mycanvas.getContext("2d");
    
  
    
 }
    
  
    
 function