Alpha Edge Blur

[FireyDeath4]

OK so I want to blur a rectangle (or it doen't matter the shape but it's a rectangle) against a transparent background. But every single one of the blurring tools don't care about the alpha at all. Every blurring tool in GIMP will just leave the rectangle's edge solid with all the contents blurred. Specifically I want to use the Motion Blur filter. The preview is always fine with the edges getting blurred and everything but even if I select the dang alpha channel there's always just a big solid rectangle with all the contents in it blurred. Is this a glitch or what? Anyone know what's going on.

Bye!

[Blighty]

Not much info to go on. In cases like this a screen print might help, showing layers dialogue etc.

A guess: Your rectangle layer is smaller than the canvas. Try Layer > Layer to image size. Do you have an active selection? Select > None.

[Espermaschine]

Perhaps you accidentally locked the alpha channel ? (unlock in the layers tab)

[Ofnuts]

It seems you are keeping a selection on the rectangle. In that case Gimp will only update pixels in the selection, leading to a solid rectangle with the contents blurred. Remove the selection on the rectangle. Below, left to right: initial image, motion blur with selection on the circle, motion blur without selection:

   

[FireyDeath4]

Done layer to image size? ✓
Unlocked Alpha channel? ✓
Selected none? ✓

If it helps, I started with a PNG that originally had no transparency to begin with. Then I resized the canvas to be bigger than the rectangle, added the alpha channel and deleted the surroundings of it. However, it turns out the former latter was wrong because apparently there was an alpha channel lock thing in the Layers tab. COME ON! Why is that there? If anything it should be working in the CHANNELS tab, just like red green and blue!

[Ofnuts]

(12-15-2018, 10:52 AM)FireyDeath4 Wrote: ... apparently there was an alpha channel lock thing in the Layers tab. COME ON! Why is that there? If anything it should be working in the CHANNELS tab, just like red green and blue!

No, because the alpha-lock is an attribute of the layer. The alpha channel is quite special anyway, if you want to paint on it you have to use  a layer mask.

[Espermaschine]

(12-15-2018, 10:52 AM)FireyDeath4 Wrote: COME ON! Why is that there?

Dude, i wouldnt know what to do without the alpha channel lock. Its the best !
Some day you will understand !

Example: quickly recolour text or a stroke ?
Lock alpha channel, drag and drop colour.
WIN !



Btw, you can also hide a selection. I always fall for that one:
make a selection, 
its in the way, 
i hide it (View -> Show Selection), 
then forget about it and wonder why i cant do anything   

[rich2005]

It is your workflow that is the problem

Image -> Resize Canvas -> Add alpha (-> Delete Surroundings-why?)

Still leaves the original layer boundary

Needs to be: Image -> Add alpha channel -> Resize Canvas with layers options "All layers" & "Transparency"




Alpha Channel locked?
Gimp is not Autonomous, if the alpha channel is locked then some time you locked it.