GIMP Version: 2.8.14
Operating System: Linux
OS Version: Linux Mint 22.3
GIMP Experience: Basic Level


I have a scan of a black-and-white pen and ink drawing made by me. The scan was saved as tif.

I need to remove the white background from the drawing. Whenever I have tried I get a white line drawing on a transparent background. The file does not seem to be acting normally.

So far, no tutorial on youtube has solved the problem.

Any help appreciated.

If as you say you get a white line drawing - have you tried inverting the colour to see what you get?

Do you mean when you try 'colour to alpha' that all of the white goes.
Your edges of a picture need to be complete to just get rid of the background.
You could do a selection around your picture with free select then invert, path tool then turn that into a selection then invert and even the foreground select inverted - actually you get a couple modes now so you can probably do background.
After getting your selection then colour to alpha and just that area will be transparent

Set the bucket-fill tool to `Color erase` mode; and `Fill whole selection`. Bucket-fill the image with white.

Haven't used TIF in a long time and didn't recall it being able to save alpha information. Best to save in PNG format; more universally accepted, imo. As for removing the white background, ofnuts explained it well. Can also try color to color to alpha (defaults to white for erasure).

I agree with lyle, the initial image was not good. Also scanners, they are redundant for most uses since hi-def cameras in mobiles (cell phones in the US).
Just take an image of your drawing with your phone and use Gimp to add an alpha channel. You will get better results.

[quote="ofnuts"]Set the bucket-fill tool to `Color erase` mode; and `Fill whole selection`. Bucket-fill the image with white.

thank you for the suggestion. It did not work for me. My steps:
1. turned tif into png
2. opened png in gimp
3. add alpha channel
4. activated "select by color" tool. I clicked on the white back ground
5. Select, none
STARTING YOUR METHOD:
6. bucket fill > color erase
7. fill type: BG color fill
8. Fill whole selection (there is also a "fill by line art detection" option)
9. then when I dragged the white square over to the canvas, the whole thing went white. I fiddled with the options but same result.

Instead of your point 9, do a bucket fill by clicking in the image window with the left mouse button.

thanks for contributing.
played around with inverting, nothing worked.

"You could do a selection around your picture with free select then invert, path tool then turn that into a selection then invert and even the foreground select inverted -"

I'm not good at the selection tools. do you mean select the entire canvas or just the triangle shape of the drawing?
then invert
then path tool...?

did not work.

I am now fiddling with add alpha channel and layer mask to see if something happens by accident.

thanks for responding.
I actually have a professional camera. I might have to retake the image and save as jpeg then convert to png in gimp
then add alpha channel....
when you export as a new file type gimp asks you to check off a few data radio buttons. I am wondering if unclicking all of these might work if something is being imported from tif that is obstructing this process.

Not really. You are very unlikely to shoot with the camera exactly perpendicular to the paper, so you will have to use perspective correction and unless you measure the paper and scale appropriately along one dimension, your aspect ratio won't even be exact. Of course, phones can play tricks (like getting the size of a sheet of paper) but that won't work in every case.

When you drag the white square you are not using the bucket-fill tool with all its options. And what is the purpose of steps 4 and 5, that cancel each other?

Can you show a screenshot of you UI just before you apply the bucket-fill?

I did not do step 5 this time.
I had a new scan directly to jpg done this time.
As an aside, I am thinking there may be 2 things going wrong. 1. maybe gimp just can't process line art like this. 2. my computer, with i5 CPU and integrated graphics, may not be strong enough.
here is the screenshot

As you can see in my first answer, the procedure works , I tried it on your image. My PC is a bit more powerful than yours (i7), but that just makes it a bit faster. It's not a make-or-break situation.

I wanted to see the options for the bucket-fill, not the selection tool (which is not used in the procedure).

I am getting all kinds of crazy results. It may be a cognitive problem of mine or malfunction of my HDD.
I will present it as black on white background for now.
can you send me your successful treatment of my drawing?

Here is my try

1. Add Alpha Channel

2. Add Layer Mask ...


Result

See attached

thank you for sending me this.
I saved it to desktop and opened it and it was completely black. I guess that means black drawing on a black background, not the checkered background that means transparency. I got some results like this in my own tests.
but when I opened it in gimp it had the transparency background so this may be usable.

your english is fine. Thank you for contributing. I was not using the layer mask in my tests. I noticed that you configured the layer mask in greyscale and you inverted the mask. I would not have thought of this.

after I saved it to my file and opened it, it came out completely reversed: black background and white drawing.

I just tried color>color to alpha
the drawing after being saved is coming out a white drawing on black. maybe good for a christmas card. But thanks for the suggestion anyway. I just attached it here, but it is barely visible. I was playing around with opacity and transparency settings.