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pyrochild

Gaussian Blur Mistreats Alpha

7 posts in this topic

Repro 1:

  • Create a new image
  • Fill the image with half-transparent white
  • Run Gaussian Blur at default radius; the whole image should noticeably darken
  • The image is noticeably darker. Check the color channels; they're definitely not white anymore

Before|After

repro1before.pngrepro1after.png

Repro 2:

  • Create a new image
  • Delete a section in the middle of the image
  • Run Gaussian Blur at default radius
  • Repeat with Ctrl+F until you see edges darkening; should be noticeable on the 5th time, and painful on the 6th

Before|After

repro2before.pngrepro2after.png

Repro 3:

  • Open an image
  • Use a transparency gradient across the whole image
  • Run Gaussian Blur at default radius
  • There should now be noticeable banding across the gradient.

Before|After

repro3before.pngrepro3after.png

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Do you have a version of the 'before' image with alpha channel?

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Do you have a version of the 'before' image with alpha channel?

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Ok I've filed a bug targeted for v4.0.

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This is fixed for 4.0, thanks to Ed Harvey.

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Pyro, I had no idea this was in fact a bug. I knew the outcome would be bad if I tried it, so I knew that I could not run GB with certain things. Thanks for pointing this out & for Ed Harvey & Rick fixing it.

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