[Matplotlib-users] getting extra colors in figure

Nicolas P. Rougier Nicolas.Rougier at inria.fr
Tue Jul 26 03:30:32 EDT 2016

I think Michael explained this bug during his lighting talk at Scipy 2016:

https://www.youtube.com/watch?v=0FVK-X_4wHs (time 56:00)

The problem is that interpolation is made on colorspace and not dataspace.


> On 26 Jul 2016, at 09:11, Eric Firing <efiring at hawaii.edu> wrote:
> On 2016/07/22 8:24 AM, Smit, Christine E. (GSFC-610.2)[TELOPHASE CORP] wrote:
>> Hi! I’m trying to plot data using imshow and ending up with more colors
>> than I specify in the colormap. This is causing problems with a downstream
>> user who is machine reading images to determine approximate data values
>> based on colors. I think the issue has something to do with rounding
>> because many colors in the image are only slightly off from the colors I
>> specified. My plots have exactly one pixel per data value, so each pixel¹s
>> color should be exactly a color in the colormap.
> Christine,
> I can reproduce this on 1.5.1, and on what will become 1.5.3 (the last of the 1.5 series) but not on the github branch for the upcoming 2.0 release.  Presumably the major image overhaul for 2.0 has fixed the problem--even though it was most likely a problem no one knew we had.
> Eric
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