CelebratePride.fsx

// Are you an F# programer with a liberal point of view?
// Do you want to show your happiness at the advancement of gay right?
// But hate the convience of using a facebook app to rainbowify your profile photo?
// Simple, use this script instead!

open System.Drawing
open System.Runtime.InteropServices
open System.Drawing.Imaging
open System.IO

let rainbowColours =
    [| Color.Red         // Richard
       Color.Orange      // of 
       Color.Yellow      // York
       Color.Green       // Gives
       Color.Blue        // Battle
       Color.Indigo      // in
       Color.Violet |]   // Vain 

let rainbowifyBitmap (file: string) =
    use bitmap = new Bitmap(file)
    let stripeHight = double bitmap.Height / double rainbowColours.Length

    let rect = new Rectangle(0, 0, bitmap.Width, bitmap.Height)
    let sourceData = bitmap.LockBits(rect, ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb); 

   
    let pixelBuffer: byte[] = Array.zeroCreate (sourceData.Stride * sourceData.Height) 

    Marshal.Copy(sourceData.Scan0, pixelBuffer, 0, pixelBuffer.Length); 

    let pixelsInStripe = pixelBuffer.Length / rainbowColours.Length
    let tintFactor = 350.

    for k in 0 .. 4 .. pixelBuffer.Length - 1 do
        let tintColour = rainbowColours.[k / pixelsInStripe]
        let b = double pixelBuffer.[k]
        let g = double pixelBuffer.[k + 1]
        let r = double pixelBuffer.[k + 2]

        let blue = b + (255. - b) *  (double tintColour.B / tintFactor) 
        let green = g + (255. - g) * (double tintColour.G / tintFactor) 
        let red = r + (255. - r) * (double tintColour.R / tintFactor)

        pixelBuffer.[k] <- byte (min 255. blue) 
        pixelBuffer.[k + 1] <- byte (min 255. green)
        pixelBuffer.[k + 2] <- byte (min 255. red)

    use resultBitmap = new Bitmap(bitmap.Width, bitmap.Height); 

    let rect = new Rectangle(0, 0, resultBitmap.Width, resultBitmap.Height)
    let resultData = resultBitmap.LockBits(rect, ImageLockMode.WriteOnly, PixelFormat.Format32bppArgb); 

   
    Marshal.Copy(pixelBuffer, 0, resultData.Scan0, pixelBuffer.Length)
    resultBitmap.UnlockBits(resultData)

    let dir = Path.GetDirectoryName(file)
    let name = Path.GetFileNameWithoutExtension(file)
    let ext = Path.GetExtension(file)
    resultBitmap.Save(Path.Combine(dir, sprintf "%s_rainbowifyed%s" name ext))

// provide your own test data!
rainbowifyBitmap @"c:\users\robert.RFQ-HUB.COM\Downloads\RobertPickering_FormalDress.jpg"