Semi-transparent background with a gradient.

[Mixxer]

(04-08-2021, 10:35 AM)rich2005 Wrote:

Quote:...I had some success with the Curves. But it is difficult to gauge when it is 100% transparent.

You can use sample points to show the colour values at specific points as you adjust the image.  https://docs.gimp.org/2.10/en/gimp-sampl...ialog.html

Quote: ...it also seems to eat into the soft edges. If I go far enough, I can actually make the edges smaller to the point where the soft edges are gone..

Indeed a problem. It would have helped if you gave information about this semi-transparent BG. Plain colour or... what?
This using a 50% transparent background with a black circular gradient planted on top. Using Colour-to-Alpha for the adjustment with sample points.
3 minutes duration https://youtu.be/D3cyiKLq9oM

It's all gray scale basically. The semi transparent background is gray. There is no color anywhere.

I checked the video, thanks. It seems he is working with color. I can't use color to alpha I guess.

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(04-08-2021, 02:49 PM)Ofnuts Wrote:

(04-08-2021, 07:01 AM)Mixxer Wrote: By the way, how can you tell the semi transparent bar is at  X=192? I don't see any numeric indication of that on that panel.

I aligned my Levels dialog over your screenshot to get an estimate, then 192=128+64 so in hex it's xC0, in other words a round number

I see.

Thanks for explaining.

[rich2005]

Quote:...snip...It's all gray scale basically. The semi transparent background is gray. There is no color anywhere.
I checked the video, thanks. It seems he is working with color. I can't use color to alpha I guess.

No need to guess, just try. You cannot break anything. With a grayscale image.

   

[Mixxer]

(04-09-2021, 03:14 PM)rich2005 Wrote:

Quote:...snip...It's all gray scale basically. The semi transparent background is gray. There is no color anywhere.
I checked the video, thanks. It seems he is working with color. I can't use color to alpha I guess.

No need to guess, just try. You cannot break anything. With a grayscale image.

Thanks. I did try. But I couldn't get anywhere.

[rich2005]

(04-14-2021, 11:23 AM)Mixxer Wrote: Thanks. I did try. But I couldn't get anywhere.

Then to avoid having to guess the properties of your image again, post a png or xcf example.

[Mixxer]

I did get some results from the levels workflow. How can I check if it's now 100% transparent? For the eye it looks to be 100% transparent.

[Krikor]

(04-14-2021, 11:34 AM)Mixxer Wrote: I did get some results from the levels workflow. How can I check if it's now 100% transparent? For the eye it looks to be 100% transparent.

Please reread the explanation given by rich2005 and verify that if alpha is equal to zero then the transparency is 100% for that point checked.

[Mixxer]

Ok, but I didn't use that workflow. I didn't use the Color to Alpha tool. I used the Levels tool. I saw no alpha info there. Is the Alpha reading available anywhere else on the GUI? Thanks.

[Krikor]

[attachment=5863]

[attachment=5863 Wrote:Mixxer pid='22987' dateline='1618405223']Ok, but I didn't use that workflow. I didn't use the Color to Alpha tool. I used the Levels tool. I saw no alpha info there. Is the Alpha reading available anywhere else on the GUI? Thanks.

With the Color Picker Tool you can check this information while browsing with this tool over the image and check the data collected in the window of that tool.
   
Considering that you know the center of the circle where the region is more opaque, finding two points in the diameter of that circle where Alpha is equal to zero, you will be able to delimit a circle outside of which alpha will be 100% transparent.