[Image-SIG] float rgba list -> Image
Chris.Barker
Chris.Barker at noaa.gov
Fri Sep 2 17:55:58 CEST 2011
On 9/2/11 12:33 AM, Ingo Randolf wrote:
> i get the RGBA-list from within blender...
ouch! I'm still amazed when folks write wrappers that use lists of
numbers for large arrays of data -- it's simple NOT the way to go --
painfully slow and memory inefficient. This is what the PEP 3118 buffer
protocol is for -- I know it's new, but I sure wish folks would use it.
Does Blender not provide a way to get some sort of efficient image
object? in this case, you may even get better performance writing an
image to file, and reading it back in with PIL.
> right now i have troubles getting numpy working in blenders bundled python (3.2)... so i could not try this proposal...
what was the problem? a simple "setup.py install" should work fine.
> making tuples out of the list (either with or without value-scaling) is too slow...
did you try making an array.array object? That's in the stdlib at least,
though the scaling will be slower than numpy
-Chris
>
> ingo
>
>
>
>
> Am 31.08.2011 um 20:51 schrieb Chris.Barker:
>
>> On 8/31/11 9:27 AM, Christoph Gohlke wrote:
>>> On 8/31/2011 7:21 AM, Ingo Randolf wrote:
>>>> 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.]
>>
>> I can't help but wonder why it's in that data structure to begin with -- as you've seen, it's a pretty painfully inefficient way to do it.
>>
>>>> i played around with putdata...
>>
>> you need it in a binary format that is compatible:
>>
>>> Consider using numpy<http://numpy.scipy.org/> and Image.fromarray.
>>
>> this is probably the best way, but you can also use an array.array object -- create an array.array of type byte from your list, then pass that in to putdata. (details left as an exercise for the reader)
>>
>> I think working with numbers in Python without numpy would be like working with text using lists of characters, rather than the string object.
>>
>> -Chris
>
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