Actually, all depend on what kind of data you want to interpolate. Data defined on a regular grid ? on a non-regular grid ? Your goal is not clear at that point because ‘interpolation’ can occur in a lot of different image processing operators.
Is it used to deform existing image data, to create new one ? etc…
For instance, if your goal is to create some smooth gradient image from a few colors, you need probably command
-resize instead of
-warp. Like this :
$ gmic 2,2,1,3 -rand 0,255 -resize 256,256,1,3,3
will create a smoothly varying colored image, where colors are linearly interpolated, like this one :