Rotate Image Hue in c#/.NET

I am on vacation at the beach with my wife and a few friends, and was perusing Stackoverflow at the house while waiting for everyone to get ready to go out. I ran across a question about how to rotate hue in code, which I myself have wondered before but never really needed to. Here's what I started with:

• I do enough design work to know the difference between HSB (also called HSV) and RGB, so I know changing the hue is extremely easy if I have the HSB value (the "H" stands for Hue!).
• I also know GDI+ in .NET works primarily in (A)RGB. I can iterate over the pixels of a Bitmap object and Get and Set the pixel value in RGB.
• There is a mathematical way to convert an RGB value to HSB and vice-versa, but I have no idea what that is.

A few minutes on Google yielded the equations, so I slammed this together in a few minutes more. The basic workflow is:

• Load an image and an amount to shift the hue by
• Iterate over all the pixels in the image
• For each pixel, convert its RGB value to HSB, change the hue, convert back to RGB, set the pixel's new RGB value
• Save the image

Here's a sample input/output:

Here's the central code which changes the hue for a single pixel:

private Color CalculateHueChange(Color oldColor, float hue)
{
    HLSRGB colorConverter = new HLSRGB(
        oldColor.R,
        oldColor.G,
        oldColor.B);
    float startHue = colorConverter.Hue;
    colorConverter.Hue = startHue + hue;
    return Color.FromArgb(
        colorConverter.Red,
        colorConverter.Green,
        colorConverter.Blue);
}

Not exactly rocket science, but interesting to me and presumably the person who asked the question. Here's the source. Disclaimer: This is *not* an efficient way to do any kind of image manipulation. It is just a proof-of-concept. Cheers!