Creating a drop shadow
Requirement: Take a PNG image that has an alpha mask and from it generate a new bitmap which has the same alpha mask but every pixel is black. Solution: private Bitmap GenerateDropShadowImage(Image image) { Bitmap bitmap = new Bitmap(image); BitmapData bits = bitmap.LockBits(new Rectangle(0, 0, bitmap.Width, bitmap.Height), System.Drawing.Imaging.ImageLockMode.ReadWrite, System.Drawing.Imaging.PixelFormat.Format32bppArgb); IntPtr bottomScanLine = bits.Scan0; int bytesPerRow = bits.Width * 4; unsafe { byte* pixelValue = (byte*)bottomScanLine.ToPointer(); for (int count = 0; count < bits.Width * bits.Height; count++) { pixelValue[0] = 0; pixelValue[1] = 0; pixelValue[2] = 0; pixelValue = pixelValue + 4; } } bitmap.UnlockBits(bits); return bitmap; }