using System;
using System.Drawing;

public static class Tint
{
    // Dominant colour of the opaque, saturated pixels (hue histogram weighted by saturation),
    // returned as a very light tint of that colour.
    public static string Light(string path, double keep)
    {
        using (var b = new Bitmap(path))
        {
            var w = new double[24]; var r = new double[24]; var g = new double[24]; var bl = new double[24];
            for (int y = 0; y < b.Height; y++)
                for (int x = 0; x < b.Width; x++)
                {
                    Color c = b.GetPixel(x, y);
                    if (c.A < 200) continue;
                    float s = c.GetSaturation(), l = c.GetBrightness();
                    if (s < 0.25f || l < 0.15f || l > 0.95f) continue;
                    int bin = (int)(c.GetHue() / 15f) % 24;
                    w[bin] += s; r[bin] += c.R * s; g[bin] += c.G * s; bl[bin] += c.B * s;
                }
            int best = 0;
            for (int i = 1; i < 24; i++) if (w[i] > w[best]) best = i;
            if (w[best] == 0) return "#F5F3F1";
            double R = r[best] / w[best], G = g[best] / w[best], B = bl[best] / w[best];
            Func<double, int> t = v => (int)Math.Round(255 - (255 - v) * keep);
            return string.Format("#{0:X2}{1:X2}{2:X2}", t(R), t(G), t(B));
        }
    }
}