Compare two lists of colors

Question

Lets say I have two lists of colors and I need to compare them. I have a function of comparing colors but I'm a little bit confused of types which function gets. How to cast them?

public bool AreColorsSimilar(Color c1, Color c2, int tolerance)
{
    return Math.Abs(c1.R - c2.R) < tolerance &&
           Math.Abs(c1.G - c2.G) < tolerance &&
           Math.Abs(c1.B - c2.B) < tolerance;
}

Here is my first list:

public static List<Color> PaletteOfSeasons()
{
    List<Color> springColors = new List<Color>();

    springColors.Add(ColorTranslator.FromHtml("#80a44c"));
    springColors.Add(ColorTranslator.FromHtml("#b4cc3a"));


    return springColors;
}

And in another list I'm pulling pixels from image:

public static IEnumerable<Color> GetPixels(Bitmap bitmap)
{
    for (int x = 0; x < bitmap.Width; x++)
    {
        for (int y = 0; y < bitmap.Height; y++)
        {
            Color pixel = bitmap.GetPixel(x, y);
            yield return pixel;
        }
    }
}

And question is, how can I compare this colors ?

Answer 1

If I understand you right:

var springColors = null;
springColors = PaletteOfSeasons(springColors);

var similarColors = GetPixels(bitmap).Intersect(springColors, new ColorComparer(tolerance));

And you need this class:

public class ColorComparer : IEqualityComparer<Color> 
{
    private _tolerance;

    public ColorComparer(int tolerance)
    {
        _tolerance = tolerance;
    }

    public bool Equals(Color x, Color y)
    {
        return AreColorsSimilar(x, y, _tolerance);
    }

    public int GetHashCode(Foo x)
    {
        return 0;
    }

    private bool AreColorsSimilar(Color c1, Color c2, int tolerance)
    {
        return Math.Abs(c1.R - c2.R) < tolerance &&
           Math.Abs(c1.G - c2.G) < tolerance &&
           Math.Abs(c1.B - c2.B) < tolerance;
    }
}

P.S. Your method PaletteOfSeasons is a little confusing. Passing list to method foolishly.

P.P.S. Use Bitmap.LockBits() to increase code performance.

P.P.P.S. Such implementation of GetHashCode isn't good. But in our situation it is OK.