[Image-SIG] New to PIL and struggling...

Fredrik Lundh fredrik at pythonware.com
Fri May 6 12:19:32 CEST 2005

"charlie clark" wrote:

> Trying to understand things: lut is effectively a palette table all set to
> the same value?
> What does lut[im.info["transparency"]] = 0 do?
> In my case its would sets lut[14] = 0
> So the real magic is im.point() which creates a single band presumably
> reacting to the transparency in the original image.

"point" just maps the source pixels through the lookup-table
(the "lut"), like this:

    for all coordinates in image:
        ... load pixel from input image ...
        pixel = lut[pixel]
        ... store pixel in output pixel ...

the result is a mask which has the value 0 for all transparent pixels
(index 14), and the value 1 for all other pixels.  "point" itself doesn't
know about transparency; it just uses the table it got.


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