Simple human skin color detection

SkinScanner.md

C# port of a simple skin color detection algorithm. Python original by SpliFF here. See also this Stack Overflow question.

Produces a lot of false positives but is great for quickly filtering a large set of unknown images.

SkinScanner.cs

using System;
using System.Diagnostics;
using System.Drawing;
using System.IO;

namespace SkinScanner
{
    class Program
    {
        static void Main(string[] args)
        {
            foreach (var dir in args)
            {
                foreach (var file in Directory.GetFiles(dir))
                {
                    try
                    {
                        using (var img = Image.FromFile(file) as Bitmap)
                        {
                            if (img != null)
                            {
                                if (HasSkin(img))
                                    Console.Out.WriteLine(file);
                            }
                            // else not an image
                        }
                    }
                    catch
                    {
                        // error reading file
                    }
                }
            }
        }

        const int MinSkinPercentage = 25;

        static bool HasSkin(Bitmap img)
        {
            int total = 0, skin = 0;

            var startx = 0;
            var endx = img.Width;
            var starty = 0;
            var endy = img.Height;
           
            //var startx = (int)(0.2 * img.Width);
            //var endx = (int)(0.8 * img.Width);
            //var starty = (int)(0.2 * img.Height);
            //var endy = (int)(0.8 * img.Height);

            for (int y = starty; y < endy; y++)
            {
                for (int x = startx; x < endx; x++)
                {
                    var p = img.GetPixel(x, y);
                    var s = IsSkin(p);
                    if (s) skin++;
                    total++;
                }
            }

            return ((double)skin / total) > (MinSkinPercentage / 100.0);
        }

        static bool IsSkin(Color p)
        {
            return p.R > 60 && (p.G < p.R * 0.85) && (p.B < p.R * 0.7) && (p.G > p.R * 0.4) && (p.B > p.R * 0.2);
        }
    }
}