HOWTO: Manipulate a PNM image

1) Extract image edge

    pamedge skin00109.pgm > skin.pgm

2) Composite (overlay) two Netpbm images together

    pamcomp -plain -opacity=0.5 heart00195.pgm skin00109.pgm mix.pgm

3) Enforce new maxval (convert to black and white)

    pnmdepth -plain 1 mix.pgm > mix_bw.pgm

4) Edge-enhance of image

    pgmenhance -plain mix_bw.pgm > mix_enh_bw.pgm

5) Flip image left to right

    pamflip -plain -lr mix_enh_bw.pgm > mix_flip.pgm

6) Invert colours in image

    pnminvert mix_flip.pgm > mix_inv.pgm

7) Cut an image from bottom

    pamcut -bottom 824 mix_inv.pgm > mix_cut.pgm

8) Create index image containing thumbnail versions of supplied images (contact sheet)

    pnmindex -across=8 heart*.pgm > heart_idx.pgm