public static void ColouriseWatermark(

			Bitmap watermark,

			Color backColor

			)

		{



			// Get the reference colour:

			Color refColor = watermark.GetPixel(0, 0);

			float refLuminance = refColor.GetBrightness();

			float backHue = backColor.GetHue();

			float backSaturation = backColor.GetSaturation();



			// Loop through all the pixels, adjusting the hue, 

			// saturation and luminance according to the desired 

			// background colour:

			// Lock the bitmap bits

			BitmapData bmData = watermark.LockBits(

				new Rectangle(0, 0, watermark.Width, watermark.Height),

				ImageLockMode.ReadWrite,

				PixelFormat.Format32bppArgb);

			IntPtr scan0 = bmData.Scan0;



			unsafe

			{

				byte * pDest = (byte *)(void *)scan0;



				for (int y = 0; y < watermark.Height; ++y)

				{

					for (int x = 0; x < watermark.Width; ++x)

					{

						// Get HLS of existing colour:

						Color pixel = Color.FromArgb(pDest[2], pDest[1], pDest[0]);

						float lumOffset = pixel.GetBrightness() / refLuminance;

						// Apply the offset to the reference luminance:

						float lumPixel = backColor.GetBrightness() * lumOffset;

						// Calculate the new colour

						HLSRGB newPixel = new HLSRGB(backHue, lumPixel, backSaturation);

						// set the values:

						pDest[0] = newPixel.Blue;

						pDest[1] = newPixel.Green;

						pDest[2] = newPixel.Red;

						// leave alpha alone

							

						// Move to next BGRA

						pDest += 4;

					}

				}

			}

			watermark.UnlockBits(bmData);

		}

 unsafe

                     {

                            byte * pDest = (byte *)(void *)scan0;



                            for (int y = 0; y < watermark.Height; ++y)

                            {

                                   for (int x = 0; x < watermark.Width; ++x)

                                   {

                                          // Get HLS of existing colour:

                                          Color pixel = Color.FromArgb(pDest[2], pDest[1], pDest[0]);

                                          float lumOffset = pixel.GetBrightness() / refLuminance;

                                          // Apply the offset to the reference luminance:

                                          float lumPixel = backColor.GetBrightness() * lumOffset;

                                          // Calculate the new colour

                                          HLSRGB newPixel = new HLSRGB(backHue, lumPixel, backSaturation);

                                          // set the values:

                                          pDest[0] = newPixel.Blue;

                                          pDest[1] = newPixel.Green;

                                          pDest[2] = newPixel.Red;

                                          // leave alpha alone

                                                 

                                          // Move to next BGRA

                                          pDest += 4;

                                   }

                            }

                     }