2D Azimuthal integration vs Polar transformation

[Marcraven]

I have been playing around with the 2D AzimuthalTransformation of pyFai just to be extremely suprised by the staggering difference in high frequency preservation with respect to e.g. skimage polar transform.
pyFAI 2D AI:

skimage warp_polar:

Is this behavior expected? I know the units are different (yes the axis names are wrong) but the 2D integration erased all the texture.

Cheers

[kif]

I have to admit this is puzzling ... can you provide the code and the image ?
Your azimuthal range looks really strange, how many azimuthal bins are you using ? Which pixel splitting scheme are you using ?

In this notbook, there is an example with peaks of less than 4 degrees of azimuthal extent which are properly reduced.
Untitled2.pdf

[Marcraven]

So this is the code I used.
skimage_vs_pyfai.pdf

[kif]

Thanks for the PDF: I agree with you, there is nothing "obviously" wrong. Maybe the parameter of the vmax option in imshow which should be 1000 rather than 200 in the last cell ?

Is it possible to get the input image to investigate further ?

[Marcraven]

I zip it because otherwise github does not let me upload it.

example.zip

[kif]

Thanks for the image.
Here is what I get:

• One needs to tune the vmax parameter to the same value as the raw image display (1000) to get the color scheme similar.
• The wrap_polar uses the origin of the detector at the top-left (not pyFAI's default), one needs to adapt the orientation to the proper value, i.e. 2
• There is still a 180° offer which is compensated with the rot3 parameter.

Now the images look the same ... except pyFAI did not perform any interpolation, rather it did histograms.

[Marcraven]

Hi @kif thanks for your prompt answer.

So I tried your code and did not work, which made me realize there was something strange with my environment.

After creating a new fresh environment, I get the same result for skimage and pyfai, even with my original code.

I will not dig into what was the conflicting package that generated this issue since for me now its solved, but if you are interested I can send you the package list.

Thanks a lot for your time.

[kif]

Untitled1.pdf

[kif]