AForge filter to convert a gray scale image to RGBA using source as alpha and user specified color for RGB

ColorizedAlpha.cs

using AForge.Imaging;
using AForge.Imaging.Filters;

namespace TextImage
{
    using System.Collections.Generic;
    using System.Drawing;
    using System.Drawing.Imaging;

    public sealed class ColorizedAlpha : BaseFilter
    {
        public Color Color { get; set; }
        // private format translation dictionary
        private readonly Dictionary<PixelFormat, PixelFormat> formatTranslations = new Dictionary<PixelFormat, PixelFormat>();

        public override Dictionary<PixelFormat, PixelFormat> FormatTranslations
        {
            get { return formatTranslations; }
        }

        public ColorizedAlpha(Color color)
        {
            Color = color;
            // initialize format translation dictionary
            formatTranslations[PixelFormat.Format8bppIndexed] = PixelFormat.Format32bppArgb;
        }

        protected override unsafe void ProcessFilter(UnmanagedImage sourceData, UnmanagedImage destinationData)
        {
            // get width and height
            int width = sourceData.Width;
            int height = sourceData.Height;

            int srcOffset = sourceData.Stride - width;
            int dstOffset = destinationData.Stride - width * 4;

            // do the job
            var src = (byte*)sourceData.ImageData.ToPointer();
            var dst = (byte*)destinationData.ImageData.ToPointer();

            // for each line
            for (int y = 0; y < height; y++)
            {
                // for each pixel
                for (int x = 0; x < width; x++, src++, dst += 4)
                {
                    dst[RGB.A] = *src;

                    if (*src > 0)
                    {
                        dst[RGB.R] = Color.R;
                        dst[RGB.G] = Color.G;
                        dst[RGB.B] = Color.B;
                    }
                    else
                        dst[RGB.R] = dst[RGB.G] = dst[RGB.B] = 0;
                }
                src += srcOffset;
                dst += dstOffset;
            }
        }
    }
}