画布图像绘制失败

Question

当调用ctx.DrawImage时，整个函数刚刚停止，这是与调用相关的所有信息。我无法弄清楚问题是什么。

其他信息： 我使用DevExtreme所以这是在Android OS

var Canvas = document.createElement("canvas"); 
var ctx = Canvas.getContext("2d"); 
Canvas.width=640; 
Canvas.height=480; 
var resultArray = []; 
var workerCount = 0; 


function onPhotoDataSuccess(imageData) { 
    smallPicture = document.getElementById('smallImage'); 
    alert("1"); 
    smallPicture.onload = function() { 
     alert("3"); 
     ctx.drawImage(showPicture, 0, 0, Canvas.width, Canvas.height); 
     alert("4"); 
     resultArray = []; 
     alert("5"); 
     workerCount = 2; 
     alert("6"); 
     barcodeNum = ""; 
     DecodeWorker.postMessage({ ImageData: ctx.getImageData(0, 0, Canvas.width, Canvas.height).data, Width: Canvas.width, Height: Canvas.height, cmd: "normal" }); 
       }; 

    alert("2"); 
    smallPicture.src = "data:image/jpeg;base64," + imageData; 
} 

Answer 1

运行你可能要更换：

ctx.drawImage(showPicture, 0, 0, Canvas.width, Canvas.height); 

有了：

ctx.drawImage(smallPicture, 0, 0, Canvas.width, Canvas.height);