I am reading the source code of an algorithm that is used to process an image. It contains the following lines of code
imfilter(image, [0.25 0 -0.25]', 'circular');
imfilter(image, [1 0 -1], 'circular');
I don't get what these kernels [0.25 0 -0.25]' or [1 0 -1] represent. Shouldn't kernels be 2D if the input is an image? What exactly do these specific kernels do to the image? I have seen several examples of imfilter being applied to an image with kernels of this form and I don't understand what the results of these operations should be (when I read the source code).
Can someone provide some intuition?