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POKineticJS toDataURL() gives incorrect padding error in Python
 

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  1. POKineticJS toDataURL() gives incorrect padding error in Python
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    <p>I have a base64 string that I've acquired from KineticJS toDataURL(). It's a valid base64 string. This fiddle shows that it is: <a href="http://jsfiddle.net/FakRe/" rel="nofollow">http://jsfiddle.net/FakRe/</a> </p> <p><strong>My Problem:</strong> I'm sending this dataURI up to my server, decoding using python, and saving on the server. However, I'm getting a padding error. Here's my code:</p> <pre><code>def base64_to_file(self, image_data, image_name): extension = re.search('data\:image\/(\w+)\;', image_data) if extension: ext = extension.group(1) image_name = '{0}.{1}'.format(image_name, ext) else: # it's not in a format we understand return None image_data = image_data + '=' #fix incorrect padding image_path = os.path.join('/my/image/path/', image_name) image_file = open(image_path, 'w+') image_file.write(image_data.decode('base64')) image_file.close() return image_file </code></pre> <p>I can get around this padding error by doing this at the top of my function:</p> <pre><code>image_data = image_data + '=' #fixes incorrect padding </code></pre> <p>After I add the arbitrary padding, it decodes successfully and writes to the filesystem. However, whenever I try and view the image, it doesn't render, and gives me the 'broken image' icon. No 404, just a broken image. <strong>What gives?</strong> Any help would be greatly appreciated. I've already spent way too much time on this as it is.</p> <p><strong>Steps to recreate (May be pedantic but I'll try and help)</strong></p> <ul> <li>Grab the base64 string from the JSFiddle</li> <li>Save it to a text file</li> <li>Open up the file in python, read in the data, save to variable</li> <li>Change '/path/to/my/image' in the function to anywhere on your machine</li> <li>Pass in your encoded text variable into the function with an name</li> <li>See the output</li> </ul> <p>Again, any help would be awesome. Thanks.</p>
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    1. USJames Rasmussen
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      1. POKineticJS toDataURL() gives incorrect padding error in Python
      1. USJames Rasmussen
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    1. COSomething else is wrong; I cannot reproduce your error. The data in the JSFiddle decodes as base 64 *directly*, without adding extra padding, and decode to a valid PNG image.
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      1. POKineticJS toDataURL() gives incorrect padding error in Python
      1. USMartijn Pieters
    2. COCheck that your `image_data` string is not truncated; `len(image_data) == 223548` for me. `import hashlib; hashlib.md5(image_data).hexdigest() == '03918c3508fef1286af8784dc65f23ff'`.
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      1. POKineticJS toDataURL() gives incorrect padding error in Python
      1. USMartijn Pieters
    3. CO@MartijnPieters Thank you so much! I checked the length, and I was getting 223573, which I thought was extremely odd. Then I noticed the data:image/png;base64, substring in the base64 image data. I wasn't aware I was supposed to remove that, and once I did, it started working immediately. If you'd like to write up an answer for the reputation, that'd be fine, otherwise I can answer it myself.
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      1. POKineticJS toDataURL() gives incorrect padding error in Python
      1. USJames Rasmussen
 

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