There are other types of filters apart from the vertical and horizontal filters we've seen so far:

Two other popular filters are as follows:

• Sobel: This filter simply adds a little bit more weight or value to the middle
• Scharr: Besides adding even more weight to the middle, this filter also adds weight to the sides

As we can see, the zeros are placed in the middle column of the Vertical, Sobel, and Scharr filters. Hence, we can say that Sobel and Scharr measure the difference between the left and right side, so, in a way, they're vertical filters.

As you might have already guessed, there are also horizontal versions of these filters:

Horizontal filters are basically a flipped version of the vertical filter. Columns turn to rows. It looks like a right-flipped version, transforming all the columns into rows.