1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
let mix (a : int) (b : int) (m : int) : int = a + (((b - a) * m) + (if b >= a then 127 else -127)) / 255
let through (mask : Mask.t) ~(before : Pixels.image) ~(after : Pixels.image) : Pixels.image =
let out = Pixels.copy before in
for y = 0 to before.height - 1 do
for x = 0 to before.width - 1 do
let m = Mask.get mask x y in
if m > 0 then
for c = 0 to 3 do
Pixels.set out x y c (mix (Pixels.get before x y c) (Pixels.get after x y c) m)
done
done
done;
out
let fill (mask : Mask.t) ((r, g, b) : int * int * int) (img : Pixels.image) : Pixels.image =
let colour = Pixels.map (fun _ _ _ _ -> (r, g, b, 255)) img in
through mask ~before:img ~after:colour