A lot of the images in Snap! are SVG images. This makes it to where you cannot edit the image in the built in image editor. The work around is to export the costume and open the image in an image editing software such as GIMP, export from GIMP as a PNG file, then import back into Snap!
On the negative, this is annoying and makes me wonder why these images are formatted as SVGs to begin with.
On the positive, it does provide a teaching opportunity to students about file types and image editing software techniques.
But still, any way to change these costumes to PNGs from with Snap!, or a way to fix the editor to handle SVGs?
We prefer SVG images because they still look crisp when resized. This is especially important for small pictures like costumes. Bitmap costumes get pixellated when resized.
We know that the vector editor (and the bitmap one, too, for that matter) needs work. It's a pretty major undertaking so it'll probably be a while before we can do it.
Meanwhile, if you use an external editor, why not export the result as SVG? Snap! will happily import the edited costume.
This works because when you get the pixels for a vector costume, it automatically converts to bitmap. Oh, and, change the alonzo (vector) in all the of costume reporters to the desired costume.