Gaussian noise generator in nip2 creates image artifacts

[mhirsch]

The Gaussian noise generator in nip2 seems to produce structured output -- I see bands in the image that should average to gray. Here's an example running Pattern_images_item.Noise_item.Gaussian_item.action with Mean 128 and Deviation 25.

For comparison, here's an example using the Magick toolkit for nip2, add Noise with type set to Gaussian, and adding it to uniform 128 value image:

Do you have any suggestions for getting the nip2 output to look close to ImageMagick?

Thanks!

[jcupitt]

Hi Matt, ouch, looks like the libvips random number generator should be improved. I've opened an issue: libvips/libvips#2642

[jcupitt]

OK, fixed, I hope. Thanks for pointing this out.

[mhirsch]

Curious - will this fix make it's way back to nip2 any time soon, since it uses vips 7? Thank you again for taking the time to solve this so quickly!

[jcupitt]

Yes, the vips7 API is just a thin skin over vips8, so all vips8 fixes get into nip2.