I have an existing image that has some stuff surrounded by a white background. I would like to switch it to a transparent background. What's the easiest way to do that? I tried setting the alpha to 0 for my Primary Color, then using the Fill tool to fill. But after I do that, if I use the color picker to pick up the color of the white stuff, it looks like the alpha is still 255. So it didn't seem to take. According to the Help, the eraser tool will do what I want, but unless I'm missing something that means I basically have to go individually erase every pixel, and I don't have the stamina for that.
I have a feeling I'm missing a MUCH easier method here, and I was hoping someone could enlighten me. Thanks in advance.