python 2.6: how to modify a PIL image from C without copying forth and back

[Stefan Behnel]

News123, 03.03.2010 01:38:
> I created a grayscale image with PIL.
>
> Now I would like to write a C function, which reads a;most all pixels
> and will modify a few of them.
>
> My current approach is:
> - transform the image to a string()
> - create a byte array huge enough to contain the resulting image
> - call my c_function, which copies over the entire image in order
>     to modify a few pixels
> How can I achieve this with the least amount of copies?

Take a look at Cython instead, it will allow you to access PIL's image 
buffer directly, instead of copying the data. It will also simplify and 
speed up your C wrapper code.

Stefan