ImageDiff (C# Console App to "diff" images)

using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;

namespace ImageDiff
{
    internal class Program
    {
        /// <summary>
        /// Reads all PNG files from inputPath, compares each image to the PNG file at comparisonImagePath
        /// and outputs a new PNG for each input file where pixels that are the same or similar color as in
        /// the comparison image set as transparent
        /// </summary>
        /// <param name="args"></param>
        private static void Main(string[] args)
        {
            const long tolerance = 150;

            string inputPath = @"C:\images\in\";
            string outputPath = @"C:\images\out\";
            string comparisonImagePath = @"C:\images\blank.png";

            var comparisonImage = new Bitmap(comparisonImagePath);
            int height = comparisonImage.Height;
            int width = comparisonImage.Width;

            foreach(string file in Directory.GetFiles(inputPath, "*.png"))
            {
                var input = new Bitmap(file);

                //Init transparent
                Bitmap output = new Bitmap(width, height);
                using (Graphics gfx = Graphics.FromImage(output))
                using (SolidBrush brush = new SolidBrush(Color.Transparent))
                {
                    gfx.FillRectangle(brush, 0, 0, width, height);
                }

                for (int x = 0; x < width; x++)
                {
                    for (int y = 0; y < height; y++)
                    {
                        Color bgColor = comparisonImage.GetPixel(x, y);
                        Color inputColor = input.GetPixel(x, y);

                        double diff = Math.Pow((inputColor.R - bgColor.R)*0.3, 2) +
                                      Math.Pow((inputColor.G - bgColor.G)*0.59, 2) +
                                      Math.Pow((inputColor.B - bgColor.B)*0.11, 2);


                        if (diff > tolerance)
                            output.SetPixel(x, y, inputColor);
                    }
                }

                output.Save(Path.Combine(outputPath, Path.GetFileName(file)), ImageFormat.Png);
                Console.WriteLine("Converted " + file);
            }
            Console.WriteLine("Done");
            Console.ReadKey();
        }
    }
}