Images for testing:
grads.png - non-compressed color image for the tests.
            There are high and low freqs.
grads-c.pgm - 32x32 grayscale cropped area of grads.png. There are high and
              low freqs.


Other files:
test.sh	- Gets the error mat/pgm between an original pgm and its compressed jpeg
          (at specified quality).

Naming conventions:
$BASE.* - Variants without compression on the original image.
$BASE-c.* - Small cropped version of $BASE.
$BASE-jpg.* - Compressed jpeg-version of $BASE.