>>2011885The right term is alpha channeling, or cutting out. Vectorizing is when you take a rasterized image and make it into something you can scale infinitely without pixelation.
>>2011886First I use fuzzy in add to selection mode to select pick out the background. In the bigger areas that didn't come out that well I manually erase. After I do that, I use the fuzzy select tool with feather edges to select the alpha channel, and then I use the stroke selection tool with the paintbrust set to color erase, and the color set to white(typically I'll set the brush size to be just enough to get any snowing off of the edges. After that I look over the image and try to find any snowing on the edges I missed, and erase those manually. For heavily colored snowing I'll use the paintbrush in color mode with the color set to white to desaturate, then I'll go back over with the color erase on white. Finally I'll upscale and do the same thing all over again.
