[Image-SIG] float rgba list -> Image

[Christoph Gohlke]

On 8/31/2011 7:21 AM, Ingo Randolf wrote:
> Hi all.
>
> I have a list with float-values describing an image like this:
> [R, G, B, A, R, G, B, A, R, G, B, A, R, G, B, A, R, G, B, A, ... etc.]
>
> the RGBA-values are from 0. - 1.
>
> is there a clever way to make a PIL-Image out of something like this?
>
>
> i played around with putdata... and came along with this, very, very slow solution:
>
> px = list-of-rgba-values-as-floats
> img = the-image
>
> #make int-tuples
> newdata = [(int(px[(x*4)]*255), int(px[(x*4)+1]*255), int(px[(x*4)+2]*255), int(px[(x*4)+3]*255)) for x in range( img.size[0] * img.size[1] )]
> Image.putdata(newdata)
>
>
> well i never saw a result, because it took too long for my short patience... ;)
>
>
> i also tried to set the values pixel-wise... this is also very, very slow...
>
>
> how to do that in a more clever way?
>
> thanks for any hints
> inx
>
>

Consider using numpy <http://numpy.scipy.org/> and Image.fromarray. For 
example:


import numpy
from PIL import Image

shape = 256, 256, 4
px = list(numpy.random.rand(shape[0]*shape[1]*shape[2]))

newdata = numpy.array(px, dtype=numpy.float32)
newdata *= 255.99998474
newdata = newdata.astype(numpy.uint8)
newdata.shape = shape

image = Image.fromarray(newdata)


Christoph