I'm trying to figure out how to make clip art out of my watercolor drawings. For example, I have a watercolor drawing of a pumpkin scanned onto my computer, and I need to know how to make the paper that is included in the scan transparent, so that I can use just the pumpkin image for designing cards, posters, calendars, etc. I want to make it into clip art. I know that Photoshop can do this, and probably Illustrator as well, but I want to know if GIMP or Photoshop Elements or any other program can also do this. Thank you so much!
This is a difficult question to answer, because without seeing the image, I just have to guess what you really want.
Clip art doesn't usually need to have a transparent background - most just have a plain white background. Is the existing background not white? If so then you could just paint it white. You can use the Paint Brush tool in both GIMP and Photoshop.
Are you planning to put the clip art onto a non-white background? Then you could create a layer mask in Photoshop or GIMP - both have that capability, or you could simply use the eraser tool on the background. You could export the resulting image as a PNG, which allows for transparent pixels. Both GIMP and Photoshop can do this.
Perhaps you want to recreate the image as vector art, using a vector image editor? That's possible in Adobe Illustrator, and also in the free software Inkscape. It's also possible to auto trace raster images into vectors using these pieces of software, however the results are never as good as recreating the vector art manually.
Use the fuzzy select in GIMP to select the background, then press Edit then Cut. You may have to mess with the threshold beforehand (I like to keep mine around 24). Also, it will be easier if you run a white paintbrush in GIMP over any shadows or discoloration in the background FIRST. Once you use the fuzzy select and cut, you can only erase with the eraser button, which is fine but I think it's a little easier to do it on the front end.
To be honest, I don't even bother using a paper scanner anymore. I use the (free) Adobe Scan app on my phone and it is absolutely incredible. You can clean up the background (or anything) before even sending it to your computer.