GIMP Version: 2.8.14
Operating System: Mac OS
OS Version: Catalina
GIMP Experience: New User

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Hello y'all!

I feel rather humbled having to ask this but here goes: I work with hundreds of screenshots of a graphical design tool the company I work for created and I would like to modify these screenshots and make the background transparent.

I have done similar things many times but our design tool seems to be using gray tones everywhere and also some drop shadows, which makes this usually quite simple task pretty involved and a manual process.

I wonder if any of you can help me automate this through a custom filter or plugin or any other means that GIMP supports, because I spend roughly 1h on a medium screenshot and I have potentially hundreds to deal with in the future.

Here is an example original and unmodified screenshot:


Here is where I want to get to (just better, the lines don't look good and I deleted some of borders by mistake):


The challenge is that our design tool creates this grid and the drop shadows and overall uses a not very high-contrast color scheme. I am creating technical content (blogs, documents, etc.) where I want to use those flows but not the ugly background.

So far, I have done this:
1. Used the fuzzy select tool to make 90%+ of the background transparent
2. Use the eraser tool to finish up the rest.

Thank you so much for any hints or tips to point me in the right direction!

Cheers.
Volker

Hi Wallace,

yes, you are right. I am modifying screenshots, not creating anything from scratch.

I thought about recreating the flows in a vector program but it is important they look similar to what our design tool produces and I think re-creating hundreds of flows might take even longer than removing the background.

Thank you for your suggestion!

Cheers.
Volker

rich2005 wrote a python script for me called 'clear_alpha.ph
It has a handy slider to adjust the alpha transparency to just where you want it on a layer(s).

http://gimpchat.com/viewtopic.php?f=25&t=16294

Possible solution:

1) Select a square that is the tile of the background pattern and copy it to the clipboard (in your image it's a 10x10 square). If you select the top right corner the next step will be easier.
2) Add a new layer, start the bucket fill tool, the the pattern to "Clipboard" (1st in list) and bucket fill. If you cut the top right corner the grid in the new pattern will be aligned with the one in the image. Otherwise you have to create a slightly wider layer, fill it and shift it to align the grids.
3) Add a layer group, move the two layers to it, pattern on top
4) Set the top layer to "Color erase" mode (this requires Gimp 2.10)
5) Add a white layer, outside the group

This removes the grid on the background, but instead you see it in some boxes:

Thank you, @tas_mania and @ofnuts!

@ofnuts, your result looks really good! I fear I won't be able to automate it, though. I think I have to focus on improving my starting position. If I can get our design tool to start with a white background instead of a gray grid, that will make it so much easier! Your approach will definitely work for individual images but I will have to deal with hundreds of screenshots of different flows. I am learning, though, how you use layers and groups to achieve what I thought was impossible. Really cool!

Thank you both!

...........Or just use the Curves tool and do it in a couple of seconds.

Hello vsheuber



This script works on my gimp 2.8.22, located at "<Image>/On test/Clean image"

Running the script on your original image gives the first image below

The second image is 10-15 minutes tidying up the top layer

The third image is after another 10-15 minutes of painting black on the mask to allow the insides of the boxes to show through

Hope it works/helps, though racer-x curves looks the way to go

Steve

Third image