Reading image dimensions before it is loaded from a web form using python.

[Cameron Laird]

In article <mailman.235.1183241587.22759.python-list at python.org>,
Evan Klitzke <evan at yelp.com> wrote:
>On 6/30/07, Norman Khine <norman at khine.net> wrote:
>> Hello,
>> I am writing an application using python that allows the user to upload
>> an image to a folder on the server.
>>
>> Is there a way to get the size of the file before it has been uploaded
>> onto the server and give an error if the size does not comply to the
>> maximum size.
>
>The easiest way to do this is to simply restrict the maximum file
>upload size. When the client makes the POST request you can see how
>big it will be. This won't really give you the image dimensions of
>course, but there's no simple way to find out that information without
>uploading the entire image.
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Maybe we disagree about "simple", but there *are* definite
ways to do so.  It's a bit involved--I fear that when Mr. 
Khine writes "image", he might have in mind not just .gif,
.jpg, and .png, but perhaps also SVG, Flash, PDF, ...--but,
yes, it's possible with most image formats to upload just a
small portion of the header and test whether what follows
meets the size requirements.