Source code in the fsharp programming language

//pure functional version ... changing a pixel color provides a new Bitmap
type Color = {red: byte; green: byte; blue: byte}
type Point = {x:uint32; y:uint32}
type Bitmap = {color: Color array; maxX: uint32; maxY: uint32} 

let colorBlack = {red = (byte) 0; green = (byte) 0; blue = (byte) 0}
let emptyBitmap = {color = Array.empty; maxX = (uint32) 0; maxY = (uint32) 0}
let bitmap (width: uint32) (height: uint32) = 
    match width, height with
    | 0u,0u | 0u,_ | _, 0u -> emptyBitmap
    | _,_ -> {color = Array.create ((int) (width * height)) colorBlack; 
            maxX = width; 
            maxY = height}
let getPixel point bitmap =
    match bitmap.color with
    | c when c |> Array.isEmpty -> None 
    | c when (uint32) c.Length <= (point.y * bitmap.maxY + point.x) -> None
    | c -> Some c.[(int) (point.y * bitmap.maxY + point.x)]
let setPixel point color bitmap =
    {bitmap with color = bitmap.color |> Array.mapi (function 
                | i when i = (int) (point.y * bitmap.maxY + point.x) -> 
                    (fun _ -> color) 
                | _ -> id)}    
let fill color bitmap = {bitmap with color = bitmap.color |> Array.map (fun _ ->color)}


//setups
//==check pixel for color function
let check bitmap color (x,y) = 
    match (getPixel {x=x;y=y} bitmap) with 
    | Some(v) -> v = color 
    | _ -> false
let allPixels i j = [for x in [0u..(i-1u)] do for y in [0u..(j-1u)] -> (x,y)]

//create new empty bitmap
let myBitmap = bitmap 0u 0u
printfn "Is empty: %b" (myBitmap = emptyBitmap)
let myBitmap2 = bitmap 1u 0u
printfn "Is empty: %b" (myBitmap2 = emptyBitmap)
let myBitmap3 = bitmap 0u 1u
printfn "Is empty: %b" (myBitmap3 = emptyBitmap)    
//create normal bitmap
let myBitmap4 = bitmap 14u 14u
printfn "Is not empty: %b" (not (myBitmap4 = emptyBitmap))    
//just check one color
printfn "Is 1,1 black: %b" (check myBitmap4 colorBlack (1u,1u))
//check out of range color
printfn "Is 100,100 nothing: %b" (not(check myBitmap4 colorBlack (100u,100u)))
//make sure all pixels are black
printfn "Is all black: %b" ((allPixels 14u 14u) |> List.forall (check myBitmap4 colorBlack)) 
//fill bitmap color
let colorWhite = {red = (byte) 255; green = (byte) 255; blue = (byte) 255}
let myBitmap5 = myBitmap4 |> fill colorWhite
printfn "Is all white: %b" ((allPixels 14u 14u) |> List.forall (check myBitmap5 colorWhite)) 
//change just one pixel
let myBitmap6 = myBitmap5 |> setPixel {x=5u;y=10u} colorBlack
printfn "Is 5,10 black: %b" (check myBitmap4 colorBlack (5u,10u))


bitmap 14u 14u
|> fill {red = (byte) 200; green = (byte) 0; blue = (byte) 10}
|> setPixel {x=5u;y=10u} {red = (byte) 0; green = (byte) 0; blue = (byte) 0}
|> getPixel {x=5u;y=10u}
|> printfn "%A"