Load an html5 canvas into a PIL Image with Django

Question

I'm trying to get the contents of an html5 canvas and pass it to my django server, where it will then be manipulated with PIL and saved as a PNG. Here's what I have so far:

From the HTML form, the user clicks the "update" button, the canvas's contents - with canvas.toDataURL() - gets dumped into a text box that is submitted via a POST form. Eventually this will be automatic, but not for now.

<input type="text" id="canvasData" name="canvasData"/>
<input type='button' value="update" onclick='jscript:updateData();'>
<canvas id="sketch"></canvas>
<script type="text/javascript">
    function jscript:updateData() {
        $('#canvasData')[0].value = $('canvas')[0].toDataURL();
    }
</script>

The canvasData is in the form of 'data:image/png;base64,iVBORw0KGgoAAAA...etc...=' when it gets sent over. Then I deal with it in django:

from PIL import Image
...
canvasData = request.POST.get('canvasData', '')
im = Image.somehowLoad(canvasData)
...
im.save('canvas.png')

And this is where i'm stuck. I can't figure out how to get the base64-encoded data url to load up the image into a usable form with PIL.

Thanks!

edit: here's the code for the bottom comment:

>>> d
'data:image/png;base64,iVBORw0K'
>>> d.strip('data:image/png;base64,')
'VBORw0K'

Answer 1

import re

datauri = 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg=='

imgstr = re.search(r'base64,(.*)', datauri).group(1)

output = open('output.png', 'wb')

output.write(imgstr.decode('base64'))

output.close()

or if you need to load it into PIL :

import cStringIO

tempimg = cStringIO.StringIO(imgstr.decode('base64'))

im = Image.open(tempimg)