Is this code creating a matrix for the image or is it doing something else?

What exactly are these 3 lines doing?

im2(:,:,1)=im1;
im2(:,:,2)=im1;
im2(:,:,3)=im1;

Answer 1

[Image Analyst]

They're creating a 3D matrix where every slice/channel/plane is the same - it's im1. So im2 can either be a color image that appears as grayscale because all 3 color channels are identical, or it can be a volumetric image (like a CT or MRI image) where all three slices/planes are the same, like you extruded the im1 image upwards.