(Tutorial) First and last lines after Sobel filtering.

[kdesnos]

In the sobel tutorial, first and last line of the output image are not properly set before being displayed, which may cause variations at each code generation.

To solve the issue:

• Sequential sobel: The sobel actor should set to black lines the first and last line of its outpit
• Parallel sobel: in the merge actor, the first and last line of the output should be set to black lines also.

In both case, adding the following code to the actors is sufficient:

memset(output, 0, width);
memset(output + (height - 1)*width, 0, width);