tcc/Services/ImageService.cs

using ImageMagick;

namespace TCC.Services
{
    public class ImageService
    {
        public ImageService() { }

        public MagickImage BoxBlurImage(Stream imageStream, int radius)
        {
            var image = new MagickImage(imageStream);
            var blurredImage = new MagickImage(image);
            var pixels = image.GetPixels();
            var blurredPixels = blurredImage.GetPixelsUnsafe();

            foreach (var pixel in pixels)
            {
                int x = pixel.X,
                    y = pixel.Y;

                long rTotal = 0, gTotal = 0, bTotal = 0;
                int pixelCount = 0;
                for (int offsetY = -radius; offsetY <= radius; offsetY++)
                {
                    for (int offsetX = -radius; offsetX <= radius; offsetX++)
                    {
                        int newX = x + offsetX;
                        int newY = y + offsetY;

                        if (newX >= 0 && newX < image.Width && newY >= 0 && newY < image.Height)
                        {
                            var pixelColor = pixels[newX, newY];
                            rTotal += pixelColor.GetChannel(0);
                            gTotal += pixelColor.GetChannel(1);
                            bTotal += pixelColor.GetChannel(2);
                            pixelCount++;
                        }
                    }
                }

                blurredPixels[x, y].SetChannel(0, Convert.ToUInt16(rTotal / pixelCount));
                blurredPixels[x, y].SetChannel(1, Convert.ToUInt16(gTotal / pixelCount));
                blurredPixels[x, y].SetChannel(2, Convert.ToUInt16(bTotal / pixelCount));
            }

            return blurredImage;
        }
    }
}