diff.cs

        public Image imageDiff(Image img1, Image img2){
            Bitmap gazou1 = new Bitmap(img1);
            Bitmap gazou2 = new Bitmap(img2);

            //画像サイズが小さい方に合わせる
            int ht = gazou1.Height;
            int wt = gazou1.Width;

            if (gazou1.Width > gazou2.Width){
                wt = gazou2.Width;
            }
            if (gazou1.Height > gazou2.Height){
                ht = gazou2.Height;
            }

            Bitmap btDiff = new Bitmap(wt,ht);
            Image imgDiff;

            for (int i = 0; i < wt; i++){
                for (int j = 0; j < ht; j++){
                    if (gazou1.GetPixel(i, j) == gazou2.GetPixel(i, j)){
                        //一致ならば比較元のピクセルデータをそのまま格納
                        btDiff.SetPixel(i, j, gazou1.GetPixel(i, j));
                    }else{
                        //不一致ならば結果に紫色を格納
                        btDiff.SetPixel(i, j, Color.BlueViolet);
                    }
                }
            }
            imgDiff = btDiff;
            return imgDiff;
        }