If you just want a 1px black border, you can just replace the texture with a transparent one. The frames actually have solid black backgrounds, and a 1px padding around all sub-objects (eg. bars) so if you remove the visible border texture, there's already a 1px "border" underneath it.
1. Open Photoshop, GIMP, etc. MS Paint will not work. If you don't have an image editor already, GIMP is free.
2. Create a new image 32 pixels wide by 32 pixels high with a transparent background.
3. Save your transparent square as a TGA file named "SimpleSquare.tga" in the same folder as the existing "SimpleSquare.blp" file.
4. Delete or rename the "SimpleSquare.blp" file. In the addon, the file is only referred to by path and name, without an extension, so you don't need to worry about converting your TGA image to the BLP format, you just need to make sure it's the only image file named "SimpleSquare" in that folder.
The problem with this approach, however, is that I use the border to display threat/aggro and dispellable debuffs. If you still want to see these statuses, you'll need to do more work, and there are several options, the easiest two of which would probably be:
1. Leave the texture alone, and modify the UpdateBorder function (in Functions.lua) to show the border only when a status is active, but hide it otherwise. You could also replace the border texture with a flat border style if you want; just keep the filled-in region about the same size, and use the in-game border size control, otherwise you'll need to do a lot more code editing to get the placement right.
Code:
if color then
self:SetBackdropBorderColor(color[1], color[2], color[3], 1, glow and ns.config.borderGlow)
else
self:SetBackdropBorderColor(0, 0, 0, 0)
end
for pos, tex in pairs(self.BorderTextures) do
self.BorderTextures[i]:SetShown(not not color)
end
2. Modify the threat and dispel highlight elements (in Frames.lua) to have actual objects instead of updating the border color, eg.
Code:
self.DispelHighlight = self.overlay:CreateTexture(nil, "OVERLAY")
self.DispelHighlight:SetAllPoints(true)
self.DispelHighlight:filter = true
This will cause the health bar to be highlighted instead of the border. Do the same for the threat element, just after this in the code.