I'm fairly sure 2D topics are welcome here too, but having seen a comment suggesting
this site is specifically oriented towards 3d
I'd like to see answers and plenty of voting here so the community consensus can be clear.
Many 2D topics such as image processing (e.g. blurring and filtering), color spaces and transforms, image compression, rasterization, antialiasing and so on are highly important in graphics programming, even when you're primarily working on a 3D renderer. IMO, those are all quite on-topic.
This stack is for graphical computation in general. 3D is definitely going to be discussed quite a bit, but it isn't the main scope.
1D, 2D, 3D, 4D, nD graphics are all on-topic so long as they are about computation and theory.
Here is another answer I wrote that outlines things you can ask yourself to determine whether or not something is on/off topic.