Re: [Matplotlib-users] Trouble with imshow

[Christoph G. <cg...@uc...>]

On 2/5/2011 1:02 PM, Eric Firing wrote:
> On 02/04/2011 02:03 PM, Christoph Gohlke wrote:
> [...]
>>
>> How about these changes to color.py (attached). This avoids copies, uses
>> in-place operations, and calculates single precision when normalizing
>> small integer and float32 arrays. Similar could be done for LogNorm. Do
>> masked arrays support in-place operations?
>>
>> Christoph
>
> Christoph,
>
> Thank you.
>
> Done (with slight modifications) in 8946 (trunk).
>
> I was surprised by the speedup in normalizing large arrays when using
> float32 versus float64.  A factor of 10 on my machine with (1000,1000),
> timed with ipython %timeit.  Because of the way %timeit does multiple
> tests, I suspect it may exaggerate cache effects.
>
> Eric


Please consider the attached patch for the _image.frombyte function. It 
avoids temporary copies in case of non-contiguous input arrays. Copying 
a 1024x1024 slice out of a contiguous 4096x4096 RGBA or RGB array is 
about 7x faster (a common case for zooming/panning). Copying contiguous 
RGB input arrays is ~2x faster. Tested on win32-py2.7.

Christoph