Re: [pygame] surfarray.pixels3d(). I'm stumped.

[Pete Shinners <pete@shinners.org>]

Jasper Phillips wrote:
> I'm trying to blur both RGB and alpha using surfarray.  I can get it to work
> with surfarray.array3d() and .array_alpha(), but it's very slow as I end up
> using Surface.set_at() to combine the results of both methods together.
You'll never want to use the Surface.set_at/get_at functions when doing 
image effects. You'll want to avoid loops like over the whole image, 
like for x in range(width): for y in range(height): it is never going to 
be fast enough.

> exceptions.TypeError: Array can not be safely cast to required type
The "3d" arrays are always Int8 type arrays. Numeric always tries to 
upcast your numbers into regular Int, it is very annoying. With a little 
care or conversion you can get the right types out.

In my old flame example I almost have an convolution filter. Let me see 
if I can do it here in email. This will do a single color channel, so 
you'll apply is separately to R, G, B, and A.

def filter3x3(src, dst, matrix):
    "src and dst must be 2d arrays of the same size"
    w, h = src.shape[0]-2, src.shape[1]-2
    intdst = Numeric.zeros((src.shape[0]-2, src.shape[1]-2))
    for x,y in [(0, 0), (1, 0), (2, 0),
                (0, 1), (1, 1), (2, 1),
                (0, 2), (1, 2), (2, 2)]:
    	intdst += src[x:x+w,y:y+w] * matrix[x,y]
    weight = Numeric.sum(Numeric.sum(matrix))
    intdst /= weight
    dst[1:-1,1:-1] = intdst.astype(Numeric.Int8)


This doesn't filter the border pixels, but I suppose extra work could be 
done for those too. To call this on the separate color channels you 
would create a pixels3d array for the source and destination, and call 
the function like this

   filter3x3(srcarray[::0], dstarray[::0], matrix)
   filter3x3(srcarray[::1], dstarray[::1], matrix)
   filter3x3(srcarray[::2], dstarray[::2], matrix)
   filter3x3(srcalphaarray, dstalphaarray, matrix)