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    <p>A while ago, I read this problem arises out of a requirement for pre-multiplied alpha channels in the bitmaps. I'm not sure if this was an issue with Windows cursors or GDI, and for the life of me, I cannot find documentation regarding this. So, while this explanation may or may not be correct, the following code does indeed do what you want, using a pre-multiplied alpha channel in the cursor bitmap.</p> <pre><code>public class CustomCursor { // alphaLevel is a value between 0 and 255. For 50% transparency, use 128. public Cursor CreateCursorFromBitmap(Bitmap bitmap, byte alphaLevel, Point hotSpot) { Bitmap cursorBitmap = null; External.ICONINFO iconInfo = new External.ICONINFO(); Rectangle rectangle = new Rectangle(0, 0, bitmap.Width, bitmap.Height); try { // Here, the premultiplied alpha channel is specified cursorBitmap = new Bitmap(bitmap.Width, bitmap.Height, PixelFormat.Format32bppPArgb); // I'm assuming the source bitmap can be locked in a 24 bits per pixel format BitmapData bitmapData = bitmap.LockBits(rectangle, ImageLockMode.ReadOnly, PixelFormat.Format24bppRgb); BitmapData cursorBitmapData = cursorBitmap.LockBits(rectangle, ImageLockMode.WriteOnly, cursorBitmap.PixelFormat); // Use either SafeCopy() or UnsafeCopy() to set the bitmap contents SafeCopy(bitmapData, cursorBitmapData, alphaLevel); //UnsafeCopy(bitmapData, cursorBitmapData, alphaLevel); cursorBitmap.UnlockBits(cursorBitmapData); bitmap.UnlockBits(bitmapData); if (!External.GetIconInfo(cursorBitmap.GetHicon(), out iconInfo)) throw new Exception("GetIconInfo() failed."); iconInfo.xHotspot = hotSpot.X; iconInfo.yHotspot = hotSpot.Y; iconInfo.IsIcon = false; IntPtr cursorPtr = External.CreateIconIndirect(ref iconInfo); if (cursorPtr == IntPtr.Zero) throw new Exception("CreateIconIndirect() failed."); return (new Cursor(cursorPtr)); } finally { if (cursorBitmap != null) cursorBitmap.Dispose(); if (iconInfo.ColorBitmap != IntPtr.Zero) External.DeleteObject(iconInfo.ColorBitmap); if (iconInfo.MaskBitmap != IntPtr.Zero) External.DeleteObject(iconInfo.MaskBitmap); } } private void SafeCopy(BitmapData srcData, BitmapData dstData, byte alphaLevel) { for (int y = 0; y &lt; srcData.Height; y++) for (int x = 0; x &lt; srcData.Width; x++) { byte b = Marshal.ReadByte(srcData.Scan0, y * srcData.Stride + x * 3); byte g = Marshal.ReadByte(srcData.Scan0, y * srcData.Stride + x * 3 + 1); byte r = Marshal.ReadByte(srcData.Scan0, y * srcData.Stride + x * 3 + 2); Marshal.WriteByte(dstData.Scan0, y * dstData.Stride + x * 4, b); Marshal.WriteByte(dstData.Scan0, y * dstData.Stride + x * 4 + 1, g); Marshal.WriteByte(dstData.Scan0, y * dstData.Stride + x * 4 + 2, r); Marshal.WriteByte(dstData.Scan0, y * dstData.Stride + x * 4 + 3, alphaLevel); } } private unsafe void UnsafeCopy(BitmapData srcData, BitmapData dstData, byte alphaLevel) { for (int y = 0; y &lt; srcData.Height; y++) { byte* srcRow = (byte*)srcData.Scan0 + (y * srcData.Stride); byte* dstRow = (byte*)dstData.Scan0 + (y * dstData.Stride); for (int x = 0; x &lt; srcData.Width; x++) { dstRow[x * 4] = srcRow[x * 3]; dstRow[x * 4 + 1] = srcRow[x * 3 + 1]; dstRow[x * 4 + 2] = srcRow[x * 3 + 2]; dstRow[x * 4 + 3] = alphaLevel; } } } } </code></pre> <p>The pinvoke declarations are found in the External class, shown here:</p> <pre><code>public class External { [StructLayout(LayoutKind.Sequential)] public struct ICONINFO { public bool IsIcon; public int xHotspot; public int yHotspot; public IntPtr MaskBitmap; public IntPtr ColorBitmap; }; [DllImport("user32.dll")] public static extern bool GetIconInfo(IntPtr hIcon, out ICONINFO piconinfo); [DllImport("user32.dll")] public static extern IntPtr CreateIconIndirect([In] ref ICONINFO piconinfo); [DllImport("gdi32.dll")] public static extern bool DeleteObject(IntPtr hObject); [DllImport("gdi32.dll")] public static extern IntPtr CreateBitmap(int nWidth, int nHeight, uint cPlanes, uint cBitsPerPel, IntPtr lpvBits); } </code></pre> <p>A few notes on the code:</p> <ol> <li>To use the unsafe method, UnsafeCopy(), you must compile with the /unsafe flag.</li> <li>The bitmap copying methods are ugly, especially the safe method, which uses Marshal.ReadByte()/Marshal.WriteByte() calls. There must be a faster way to copy bitmap data while also inserting alpha bytes.</li> <li>I do assume that the source bitmap is able to be locked in a 24 bits per pixel format. This should not be a problem, though.</li> </ol>
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    1. POWindows Forms: Making a cursor bitmap partially transparent
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    1. COAwesome! I look forward to testing this tomorrow and embed it into my code. Gazillion thanks!
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    2. COI'd like to use part of your code regarding a class CustomCursor on article I'm preparing. Also I'd like to know if any updates exists regarding same issue.
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