+- Gimp-Forum.net (https://www.gimp-forum.net)
+-- Forum: GIMP (https://www.gimp-forum.net/Forum-GIMP)
+--- Forum: General questions (https://www.gimp-forum.net/Forum-General-questions)
+--- Thread: Can't get a clean Select by color background (/Thread-Can-t-get-a-clean-Select-by-color-background)
Can't get a clean Select by color background - rdoty - 03-02-2025
I've got several photos of items (lots of white with color images) that are taken with a backdrop. I want to make the background transparent. Initially I used a white backdrop which was marginal. Then I switched to a light blue which wasn't much better. Finally I changed to a dark Navy blue background and I figured the high contrast would be ideal. Unfortunately I can't get rid of the background compleltely.
My first attempt was with Fuzzy Select and when I clicked on the background it turned the entire image red. Playing with all the settings (anti alias, draw mask, alpha channel) I just couldn't get it to work. Never could get the Feather to activate. So then I switched to Select by Color and that worked - mostly. The problem is that the backdrop, which is a solid color, has some minor undulations which cause slight variations in color density. The result is that some of these variations leave a shimmering effect which when saved aren't completely transparent. There's still lots of contrast between the image and background so that baffles me. I'm using Inkscape as the graphics editor and I'm a real amateur with Gimp so I could use come help.
RE: Can't get a clean Select by color background - Ofnuts - 03-02-2025
Nothing says you should leave the background as it is. The important/difficult part is where the background meets the subject, the rest can be bluntly erased.
If you use Inkscape then you are familiar with paths and one of best ways to separate the subject from the background is with a clipping path. You can do that in Gimp with the Paths tool, but inkscape has a "Trace bitmap" function that can do a good deal of the work.
RE: Can't get a clean Select by color background - sallyanne - 03-03-2025
Adding onto the previous answer with gimp. When you have finally got your background transparent (Try changing the threshhold of your fuzzy select to remove the background) save that as a png or another file that does support transparency. You will always have that as is then.
Safest way when you want to make the background a colour you like, add another layer and make it the colour you like - dropping the layer to the bottom. Then you can be sure it will fill in all of the area that is transparent.
If you don't like that colour layer, delete the layer and add another and do it all over again until you get the colour you like.
NEVER fill in the area that you have just got rid of from your original picture unless you are really sure what you want and that it will work.
Feathering cannot be too large either as you will end up with a white border around your image. [small for small images and larger for large images]
RE: Can't get a clean Select by color background - Ofnuts - 03-03-2025
(11 hours ago)sallyanne Wrote: NEVER fill in the area that you have just got rid of from your original picture unless you are really sure what you want and that it will work.
Feathering cannot be too large either as you will end up with a white border around your image. [small for small images and larger for large images]
You should look into the Behind mode of the paint tools. It just fills the transparency perfectly.