Incosistent results on Firefox and Chrome while assigning base64 image data as src to image

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I am trying to draw checkbox image on canvas by assigning base64 image data as src to image object.It works fine on IE but give inconsistent results on Firefox and Chrome Here is my code

JavaScript

img = document.createElement('img');
    img.src = 'data:image/gif;base64,R0lGODlhDgAPAPcAAAAAAIAAAACAAICAAAAAgIAAgACAgMDAwMDcwKbK8BxRgCGhIeLi3ePj3+Xl4efn4+rq5uzs6e/v7PHx7/Pz8fX18/f39vn5+Pr6+fz8+/39/f7+/v///wAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAP/78KCgpICAgP8AAAD/AP//AAAA//8A/wD//////yH5BAAAAAAALAAAAAAOAA8AhwAAAIAAAACAAICAAAAAgIAAgACAgMDAwMDcwKbK8BxRgCGhIeLi3ePj3+Xl4efn4+rq5uzs6e/v7PHx7/Pz8fX18/f39vn5+Pr6+fz8+/39/f7+/v///wAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAP/78KCgpICAgP8AAAD/AP//AAAA//8A/wD//////whzADkIHEiQoIKDCBMi5KCAgcMGDh5AiCBhAgUFDB9GnFiRQgWMDSFKpDhhQQULIEVyLLnAwgWQEReQXEDzAgaQEmmyXGAzA8iJNIP21AByZk0MGTRsANmxAk+kShkytHhy6AaBID26hHoVK0OFYDEWHDswIAA7';
    ctx.drawImage(
        img,
        sx, 
        sy, 
        sw, 
        sh, 
        dx, 
        dy, 
        dw, 
        dh      
        );

If i put an alert after assigning src to image then it works with FF and chrome even.I guess its all because of javascript asynchronous behaviour, before complete src is assigned to image the drawing process takes place hence not getting complete image. Could any one tell me how to handle this problem .

Posted 30-Jul-12 20:40pm

Dexter11

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enhzflep · Answer 1 · 2012-07-31T03:31:00

I can think of two approaches I've seen before.

use an ontimeout call to set an arbitrary length delay
set a function to handle img.onload

The second method is by far the better of the two - it waits as long as is necessary, no less, no more.

You could probably do it with something like this:

JavaScript

img = document.createElement('img');
img.onload = funtion() { ctx.drawImage(img,sx,sy,sw,sh,dx,dy,dw,dh); }
img.src = imgSrcDataGoesHere;

You may run in to trouble if the code that follows img.src = imgSrcDataGoesHere; exits before the img data is decoded. If that happens, you could use a closure wrapped around the local vars to make sure they still exist when you need them.