My first imageprocessor IGraphicsProcessor

OverlayWithLinearGradient.cs

public class OverlayWithLinearGradient : IGraphicsProcessor
    {
        public OverlayWithLinearGradient()
        {
            this.DynamicParameter = Tuple.Create(Color.PaleVioletRed, Color.CornflowerBlue);
            this.Settings = new Dictionary<string, string>();
        }


        public dynamic DynamicParameter
        {
            get;
            set;
        }

        public Dictionary<string, string> Settings
        {
            get;
            set;
        }


        public Image ProcessImage(ImageFactory factory)
        {
            // Greyscale image
            var greyscale = factory.Saturation(-100); // desaturate for now
            var source = greyscale.Image;

            // Create gradient, same size as image
            var gradientColors = (Tuple<Color, Color>)this.DynamicParameter;
            var gradient = new Bitmap(source.Width, source.Height, PixelFormat.Format32bppPArgb);
            gradient.SetResolution(source.HorizontalResolution, source.VerticalResolution);
            gradient = Effects.LinearGradient(gradient, gradientColors.Item1, gradientColors.Item2);

            
            // Multiply greyscale x gradient
            try
            {
                using (FastBitmap sourceBitmap = new FastBitmap(source))
                {
                    for (var x = 0; x<sourceBitmap.Width; x++)
                    {
                        for (var y = 0; y < sourceBitmap.Height; y++)
                        {

                            var srcColor = sourceBitmap.GetPixel(x, y);
                            var destColor = gradient.GetPixel(x, y);
                            
                            // Instead of div by 255, work in 16bit, then 2 shifts and 2 adds to 8bit
                            int ta = (srcColor.A * destColor.A) + 128;
                            int tr = (srcColor.R * destColor.R) + 128;
                            int tg = (srcColor.G * destColor.G) + 128;
                            int tb = (srcColor.B * destColor.B) + 128;

                            byte ba = (byte)(((ta >> 8) + ta) >> 8);
                            byte br = (byte)(((tr >> 8) + tr) >> 8);
                            byte bg = (byte)(((tg >> 8) + tg) >> 8);
                            byte bb = (byte)(((tb >> 8) + tb) >> 8);
                            
                            // Update pixel
                            sourceBitmap.SetPixel(x, y, Color.FromArgb(ba, br,bg,bb));
                        }
                    }

                    
                }


                return source;
            }
            catch (Exception ex)
            {
                throw new ImageProcessingException("Error processing image with " + this.GetType().Name, ex);
            }
        }
    }

Do you have an example of the expected output (maybe using CSS blend mode to compare against?)