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POExtending c functionality of PIL
 

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    <p>I want to create functionality similar to PIL's <code>Image.blend</code>, using a different blending algorithm. To do this would I need to: (1) directly modify the PIL modules and compile my own custom PIL or (2) write a python c module which imports and extends PIL?</p> <p>I have unsuccessfully tried:</p> <pre><code>#include "_imaging.c" </code></pre> <p>I also was trying to just pull out the parts I need from the PIL source and put them in my own file. The farther I got in the more things I had to pull and it seems that is not the ideal solution.</p> <p><strong>UPDATE:</strong> edited to add the blending algorithm implemented in python (this emulates the overlay blending mode in Photoshop):</p> <pre><code>def overlay(upx, lpx): return (2 * upx * lpx / 255 ) if lpx &lt; 128 else ((255-2 * (255 - upx) * (255 - lpx) / 255)) def blend_images(upper = None, lower = None): upixels = upper.load() lpixels = lower.load() width, height = upper.size pixeldata = [0] * len(upixels[0, 0]) for x in range(width): for y in range(height): # the next for loop is to deal with images of any number of bands for i in range(len(upixels[x,y])): pixeldata[i] = overlay(upixels[x, y][i], lpixels[x, y][i]) upixels[x,y] = tuple(pixeldata) return upper </code></pre> <p>I have also unsuccessfully tried implementing this using scipy's <code>weave.inline</code>:</p> <pre><code>def blend_images(upper=None, lower=None): upixels = numpy.array(upper) lpixels = numpy.array(lower) width, height = upper.size nbands = len(upixels[0,0]) code = """ #line 120 "laplace.py" (This is only useful for debugging) int upx, lpx; for (int i = 0; i &lt; width-1; ++i) { for (int j=0; j&lt;height-1; ++j) { for (int k = 0; k &lt; nbands-1; ++k){ upx = upixels[i,j][k]; lpx = lpixels[i,j][k]; upixels[i,j][k] = ((lpx &lt; 128) ? (2 * upx * lpx / 255):(255 - 2 * (255 - upx) * (255 - lpx) / 255)); } } } return_val = upixels; """ # compiler keyword only needed on windows with MSVC installed upixels = weave.inline(code, ['upixels', 'lpixels', 'width', 'height', 'nbands'], type_converters=converters.blitz, compiler = 'gcc') return Image.fromarray(upixels) </code></pre> <p>I'm doing something wrong with the <code>upixel</code> and <code>lpixel</code> arrays but I'm not sure how to fix them. I'm a bit confused about the type of <code>upixels[i,j][k]</code>, and not sure what I could assign it to.</p>
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    1. COIf you are willing to post your algorithm, I bet we can recreate it in NumPy and get all the speed of the compiled C code. Similar to this Q/A: http://stackoverflow.com/questions/2034037/image-embossing-in-python-with-pil-adding-depth-azimuth-etc Otherwise, look into cython: http://cython.org/
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    2. COI just edited my question and put an example in. It does what I want in pure python but I am looking to speed it up.
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