GIMP

HOW TO

Give an image a transparent background

This method works if ONLY the background is white.

1. Layers -> Transparency > Add Alpha Channel
2. Colors -> Color to Alpha
3. Change background to transparent

This will selectively erase

1. Layers -> Transparency > Add Alpha Channel
2. Select background with Magic Wand
3. Use Eyedropper to select the background color
4. Use Bucket Fill
   1. Set opacity to 100%
   2. Set Mode to Color Erase option
   3. Use BG Fill

Thanks https://graphicdesign.stackexchange.com/questions/5446/making-the-background-of-an-image-transparent-in-gimp#5454

Install

on a machine you don't own see Portable Windows