I am working on a simple drawing game and I need to get a Flood Fill algorithm working for a Paint Bucket tool.

I have the game running on WinForms at the moment which is extremely slow, but I have a working Flood Fill algorithm there, I could get the code to support SharpDX if I could get the color of a pixel (either from a SharpDX.Direct2D1.Bitmap or from a SharpDX.Direct2D1.RenderTarget), but I can't find a way to do so.


Since the algorithm I am using accepts System.Drawing.Bitmap I only needed a way to capture a rendered frame onto one and then render the result, this is far from efficient but I've got a solution.

The solution uses PrintWindow from the WIN API.

public static extern bool PrintWindow(IntPtr hWnd, IntPtr hdcBlt, int nFlags);

This would probably only work if an embedded SharpDX control is used as capturing the control via handle won't do, but capturing a parent control, in this case the form, will return the desired image.

System.Drawing.Bitmap bmp = new System.Drawing.Bitmap(Width, Height, System.Drawing.Imaging.PixelFormat.Format32bppArgb);

Graphics g = Graphics.FromImage(bmp);
IntPtr hdcBitmap = g.GetHdc();

PrintWindow(Handle, hdcBitmap, 0);


// Crop the image to return only the part that we need, without control borders.
bmp.Clone(new Rectangle(SharpDXControl.Location.X + 1, SharpDXControl.Location.Y + 1, SharpDXControl.Width - 2, SharpDXControl.Height - 2), bmp.PixelFormat);

To draw the image, I created a new SharpDX.Direct2D1.Bitmap instance and used the pixel data (bits) from the System.Drawing.Bitmap instance.

SharpDX.Direct2D1.Bitmap dxbmp = new SharpDX.Direct2D1.Bitmap(renderTarget, new SharpDX.Size2(bmpWidth, bmpHeight), new BitmapProperties(renderTarget.PixelFormat));
dxbmp.CopyFromMemory(bmpBits, bmpWidth * 4);
renderTarget.DrawBitmap(dxbmp, 1F, SharpDX.Direct2D1.BitmapInterpolationMode.Linear);

The algorithm I am using is a slightly modified version of the Queue-Linear Flood Fill Algorithm.


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