Even if you don’t work with masses of layers in your GIMP files, you can still benefit from understanding how Layer Groups work, as they’ll help you better manage files, especially when it comes to sharing them with others.
Why Use Layer Groups?
It helps to think of layers as individual sheets of transparent acetate, each with a different image on them. If you were to stack these sheets on top of each other, the clear transparent areas would allow layers lower down the stack to give the impression of a single composite image. The layers can also easily be moved to produce different results. In GIMP, the layers are similarly virtually stacked up on top of each other. By using layers with transparent areas, the lower layers will show through resulting in a composite image that can be exported as a flat file, such as a JPEG or PNG. By keeping the separate elements of the composite image in separate layers, you can return to the layered file and easily edit it before saving a new flattened file. This is especially helpful when, for example, a client wants you to make small edits to a submitted image, such as making a logo slightly larger.
Using Layer Groups in The Layers Palette
Follow these steps to create a new Layer Group in GIMP. Just as with layers, you can duplicate groups by selecting one and choosing Duplicate in the bottom of the Layers palette. The visibility of a Layer Group can be turned off, and you can use the opacity slider to make the group semi-transparent. Notice that each Layer Group has a small button next to it with a plus or minus symbol. These can be used to expand and contract layer groups; they are used to toggle between the two settings.
