Blur tool blending black into the layer

this has been occurring ever since I started using krita and i just dont know why.
whenever i use any of the blur filter, It’ll blend black color around the edge when there were no black color to begin with.


I don’t see that happening.
Are you using 8-bit RGB/A with the default colour profile and is the layer blending mode Normal?

Can you post a full screen screenshot (.png)?


Transparency lock is enabled for that layer, so it’s a little bit open to interpretation what should happen when blurring.

Right now it looks like the RGB pixels are multiplied with the alpha before blurring, which is pretty standard. The options here are:

-premultiply RGB ( what it seems to do now)
-allow blurred pixels to turn transparent despite the lock.
-run some kind of edge extend algorithm before blurring.

okay, I’ll see if these work, ty!

Sorry, I meant these are what the software can choose to do in this kind of situation. For your use case, if instead of transparency lock you used a transparency mask for that layer, that would let you have enough pixels past the edge to blur.

This is why a full screen screenshot is so useful for figuring out problems :slight_smile:

If you want to restrict the region of blur, another way is to blur a copy that has alpha inherited from the original:

If alpha inheritance produces the expected result, then maybe this is an actual bug…

The alpha inheritance is a cosmetic masking treatment that masks out the blur spread outside the original, during compositing. The original blur spread is still there on the Copy layer.

I think that blurring on a layer that has alpha lock is a complex thing to consider as you pointed out in your previous reply.
The bringing in of black, as was seen, is something that I’d leave to a developer to think about.

Yes, but what does the alpha masked layer do about the transparent pixels that get blurred inwards?

I’m guessing the operations in that case are something like premultiply → blur > unpremultiply → apply inherited alpha > premultiply

this isnt really working for me cuz the blurred layer becomes transparent and you can see the hard seperated colors underneath

I’m not sure which operation you’re referring to.

From what little I’ve read, a new paint layer has a default pixel that is black and transparent. Maybe it’s that default black colour that is being brought in?

what ive found to work tho is use alpha lock and blur still but then use gradient map, but yknow thats pretty tedious to use so i hope a developer sees this.

This is getting complicated. I don’t see any edge effects:


(I still had it open in a different workspace so I could do that quickly.)

so apparently that’s the case
I used the fill tool first and then went over the entire thing with a brush and the blending came out fine

nvm its being annoying again

I always get the black being brought in with alpha lock on the layer.

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I get the alpha lock black when using a Filter as shown above, but not when using a Filter Mask instead. I dunno why there’s a difference.

The filter mask operates on the composited layer image and doesn’t affect the pixels of the layer. As such, it doesn’t give the required end result anyway.
It also has an upper limit of 100px blur radius for some reason.

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With a higher radius, the filter mask would slow down compositing the image so much that it becomes unusable.