AForge.Math.Random.UniformGenerator.Next C# (CSharp) Method

        public double Next()
        {
            return rand.Next()*length + min;
        }

        public static Bitmap Additive(Bitmap image, Rectangle region, int amount)
        {
            int startX = region.Left;
            int startY = region.Top;
            int stopX = image.Width - 1;
            int stopY = image.Height - 1;
            if (startX + region.Width < image.Width)
            {
                stopX = startX + region.Width;
            }
            if (startY + region.Height < image.Height)
            {
                stopY = startX + region.Height;
            }

            Bitmap b = new Bitmap(image);
            BitmapData bmpData = b.LockBits(new Rectangle(0, 0, b.Width, b.Height), ImageLockMode.ReadWrite, b.PixelFormat);
            IntPtr ptr = bmpData.Scan0;
            int stride = bmpData.Stride;

            int bytes = Math.Abs(bmpData.Stride) * b.Height;
            byte[] rgbValues = new byte[bytes];

            System.Runtime.InteropServices.Marshal.Copy(ptr, rgbValues, 0, bytes);

            IRandomNumberGenerator generator = new UniformGenerator(new Range(-amount, amount));
            Parallel.For(startY, stopY, y =>
            {
                for (int x = startX; x < stopX; x++)
                {
                    int i = y * stride + x * 4;
                    rgbValues[i] = (byte)Math.Max(0, Math.Min(255, rgbValues[i] + generator.Next()));
                    rgbValues[i + 1] = (byte)Math.Max(0, Math.Min(255, rgbValues[i + 1] + generator.Next()));
                    rgbValues[i + 2] = (byte)Math.Max(0, Math.Min(255, rgbValues[i + 2] + generator.Next()));
                }
            });
            System.Runtime.InteropServices.Marshal.Copy(rgbValues, 0, ptr, bytes);
            b.UnlockBits(bmpData);

            return b;
        }