Strange pixels as noise added post-registration

[markbuckup]

Hello,

When performing an affine or bspline on my image, strange, dark pixels appear throughout the image. I initially thought this made sense for bspline, as space is being warped and x,y coordinates are left without original RGB values, but I'm also seeing it for the affine?

Is there a way to prevent this? Or is there a way to collect the indices of these pixels so I can account for them myself?

Thanks!

mark

[sorenchr2011]

Hi, If this is RGB images and you are using bspline interpolation for the final resampling then you can get values outside of the valid range (do you could have pixels with value 256 there even if input max was 255). Is your image output type float? What is the range of the transformed image? Soren

On Thu, Aug 13, 2020, 22:36 markbuckup [email protected] wrote:

Hello,

When performing an affine or bspline on my image, strange, dark pixels appear throughout the image. I initially thought this made sense for bspline, as space is being warped and x,y coordinates are left without original RGB values, but I'm also seeing it for the affine?

Is there a way to prevent this? Or is there a way to collect the indices of these pixels so I can account for them myself?

Thanks!

mark [image: Screen Shot 2020-08-13 at 16 32 46] https://user-images.githubusercontent.com/56090031/90184406-0efae780-dd83-11ea-85d3-2081ebc11aaa.png

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[mynschen]

@markbuckup thanks for asking. I'm facing a similar problem @sorenchr2011 thanks for pointing this out. Any simple solution to this issue you would recommend? I've tried some other interpolation methods but the noises persisted. In my case, I have greyscale image as moving image while color image as fixed image. Looking forward to any comment. Thanks =)

[mynschen]

I figured out that my pixel noises were generated using np.uint8(), which takes 0.0 as 255 (np.uint8(0.0)=255). A simple solution to this issue: rI = sitk.GetArrayFromImage(resultImage) rI = rI*(rI>0) + (rI<=0) Then np.uint8(rI) will be noise-free.

[heyblackC]

a more simple solution: resultImage = sitk.Threshold(resultImage, 0.0001, 1e9, 0.00001) this line can force 0.0 to become a number which is > 0.0, and it works in my computer. @mynschen ,you are right!