What I'm Trying To Do: I have about 80 pngs of "cards", and I want to paste first of all a black border with rounded corners over top of the images, and then have the outside parts of the rounded corners be "transparent color".
What Works But Painfully: One thing that works is having a "template" file open in a separate file tab that contains the image of the curvy black border in the normal visible section of a layer, and then a "layer mask" for it that shows what part is supposed to be transparent outside the round corners. So the steps for each image are:
- Open the next card image as a new "tab" in GIMP
- Copy the visible part of the image (the black border) from the template's tab
- Back to Card tab and paste image onto the visible part of the card
- Go back to the template tab, select "show mask", and then do a copy of THAT
- Go back to the card tab
- Select Add Layer Mask and let it add an empty one
- Select "Show Mask"
- Paste (and so now the transparency data is pasted)
- Export the result as a PNG
(Note that this whole process above involves the "template" and each individual card being opened as a separate file in Gimp - different tabs along the top. So it's a LOT of fidgety little steps for each card, when of course I'd rather be doing these things at least a little more en masse).
What I Can't Figure Out How To Do Right: What I think I ought to be able to do is use "Open as Layers..." on all the various PNG files, which opens a whole bunch of layers with one fell swoop and loads the original card images into there. And then I'd have my card template in there as another layer I guess. And then somehow I'd be able to apply the visible part of my important layer on top of each card, somehow I'd be able to duplicate the layer mask and apply it to all the other layers (the ones with the cards in them), and then I could export each individual layer back out as its own file. But apart from the "open as layers" part, I can't figure out how to do any of it -- to apply things from one layer to another, or copy layer masks from one layer to another, etc.
Basically I picture a process a lot more like "hitting Ctrl+V about 80 times" (or maybe once each for images & masks) and a lot less like doing-a-whole-bunch-of-fidgety-steps 80 consecutive times.
I don't have much experience working with "multiple layers", and that obviously shows.