Proving Reliability of Image Processing Techniques in Digital Forensics Applications

Listing 9

Definitions of operations over pixels and images.

	Definition eqbcol (c1 c2: color): bool :=
	match c1, c2 with
	|white, white ⇒ true
	|black, black ⇒ true
	|_, _ ⇒ false
	end.
	Definition negcolor (c: color): color:=
	match c with
	|white ⇒ black
	|black ⇒ white
	end.
	Definition negpix (p: pixel): pixel:=
	match p with
	|Br,c,col ⇒ Br,c, negcolor col
	end.
	Fixpoint negimage (pic: image): image:=
	match pic with
	|nil ⇒ nil
	|cons p tl ⇒ cons (negpix p) (negimage tl)
	end.
	Fixpoint eqpixel (p1 p2: pixel): bool :=
	match p1, p2 with
	|Br,c,col, Brʹ,cʹ,colʹ ⇒
	andb (andb (r = ? rʹ) (c = ? cʹ)) (eqbcol col colʹ)
	end.
	Fixpoint negpiximg (p: pixel) (img: image): image:=
	match img with
	|nil ⇒ nil
	|cons pʹ ⇒ if eqpixel p pʹ then
	cons (negpix pʹ) (negpiximg p tl)
	else cons pʹ (negpiximg p tl)
	end.