This example convolves an input image with a filter for edge detection. The input image must be in the pgm format. Images in most formats can be converted to pgm with ImageMagick. For example, converting titus.png should give you titus.pgm:
convert titus.png test.pgm
diff test.pgm titus.pgm # output should be empty
Running this example on the titus.pgm should give you a result in pgm format, which,
once converted back to png, should look like the following:
pushd ../../build
./examples/image-processing/image-processing ../examples/image-processing/titus.pgm
popd
convert titus.pgm.out.pgm titus_out.png