image to ascii

img2ascii.fsx

let Color2Gray (c:Color) =
    //((float)c.R * 0.3) + ((float)c.G * 0.59) + ((float)c.B * 0.11)
    ((float)c.R * 0.2126) + ((float)c.G * 0.7152) + ((float)c.B * 0.0722)

let Image2Ascii (img:Image) = 
    let mutable n_h = 60
    let mutable n_w = 80

    n_h <- (int)((float)img.Height * (float)n_w/(2.1 *(float)img.Width)) //calculate resized height

    if n_h > 60 then
        n_h <- 60
        n_w <- (int)((float)img.Width * 2.1 * (float)n_h/(float)img.Height)

    use bmp = new Bitmap(img,new Size(n_w,n_h)) //resize
    //let asciiMap = [|' ';'.';',';':';';';'o';'x';'%';'#';'@'|]
    let asciiMap = [|'`';'\'';'.';',';':';';';'i';'+';'o';'*';'%';'&';'$';'#';'@'|]
    for y in [|0 .. bmp.Size.Height-1|] do
        for x in [|0 .. bmp.Size.Width-1|] do
           //convert to grayscale
           let grayScale = Color2Gray (bmp.GetPixel(x,y))
           let scaled = (grayScale * float(Array.length(asciiMap)-1) /255.0)
           let index = (int)(scaled + 0.5)
           printf "%c" asciiMap.[index]
        printfn ""
    printfn ""