How to get started to do Sobel
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First make sure that you can download images from the class website.
Then, ensure that you have a viewer to be able to see these images.
Then, download the sobel.c code from the website.
Study the sobel.c code carefully, ensure you understand the issues within it.
You can also look at diffpic3.c and rawtopgm.c   for additional steps and
insight.

Then modify the sobel.c code to print its output to a file, and to include the
three header lines.

Then compile the sobel code. If it compiles, run it and give it the
information that it needs about the file names and/or any thresholds.

Then look at the output file that is generated from sobel, it must have
size around 65551 (definitely not 65536).

Then put the output in the viewer to see that it looks like the sobelmag.pgm
output of the website.

Then, to do the assignment part A, add the thresholding code for the High and
the Low, and finish everything for part A.