Need Help Setting an Image with Transparent Background to Clipboard
- by AMissico
I need help setting a transparent image to the clipboard. I keep getting "handle is invalid". Basically, I need a "second set of eyes" to look over the following code. (The complete working project at ftp://missico.net/ImageVisualizer.zip.)
This is an image Debug Visualizer class library, but I made the included project to run as an executable for testing. (Note that window is a toolbox window and show in taskbar is set to false.) I was tired of having to perform a screen capture on the toolbox window, open the screen capture with an image editor, and then deleting the background added because it was a screen capture. So I thought I would quickly put the transparent image onto the clipboard. Well, the problem is...no transparency support for Clipboard.SetImage. Google to the rescue...not quite.
This is what I have so far. I pulled from a number of sources. See the code for the main reference. My problem is the "invalid handle" when using CF_DIBV5. Do I need to use BITMAPV5HEADER and CreateDIBitmap?
Any help from you GDI/GDI+ Wizards would be greatly appreciated.
public static void SetClipboardData(Bitmap bitmap, IntPtr hDC) {
const uint SRCCOPY = 0x00CC0020;
const int CF_DIBV5 = 17;
const int CF_BITMAP = 2;
//'reference
//'http://social.msdn.microsoft.com/Forums/en-US/winforms/thread/816a35f6-9530-442b-9647-e856602cc0e2
IntPtr memDC = CreateCompatibleDC(hDC);
IntPtr memBM = CreateCompatibleBitmap(hDC, bitmap.Width, bitmap.Height);
SelectObject(memDC, memBM);
using (Graphics g = Graphics.FromImage(bitmap)) {
IntPtr hBitmapDC = g.GetHdc();
IntPtr hBitmap = bitmap.GetHbitmap();
SelectObject(hBitmapDC, hBitmap);
BitBlt(memDC, 0, 0, bitmap.Width, bitmap.Height, hBitmapDC, 0, 0, SRCCOPY);
if (!OpenClipboard(IntPtr.Zero)) {
throw new System.Runtime.InteropServices.ExternalException("Could not open Clipboard", new Win32Exception());
}
if (!EmptyClipboard()) {
throw new System.Runtime.InteropServices.ExternalException("Unable to empty Clipboard", new Win32Exception());
}
//IntPtr hClipboard = SetClipboardData(CF_BITMAP, memBM); //works but image is not transparent
//all my attempts result in SetClipboardData returning hClipboard = IntPtr.Zero
IntPtr hClipboard = SetClipboardData(CF_DIBV5, memBM);
//because
if (hClipboard == IntPtr.Zero) {
// InnerException: System.ComponentModel.Win32Exception
// Message="The handle is invalid"
// ErrorCode=-2147467259
// NativeErrorCode=6
// InnerException:
throw new System.Runtime.InteropServices.ExternalException("Could not put data on Clipboard", new Win32Exception());
}
if (!CloseClipboard()) {
throw new System.Runtime.InteropServices.ExternalException("Could not close Clipboard", new Win32Exception());
}
g.ReleaseHdc(hBitmapDC);
}
}
private void __copyMenuItem_Click(object sender, EventArgs e) {
using (Graphics g = __pictureBox.CreateGraphics()) {
IntPtr hDC = g.GetHdc();
MemoryStream ms = new MemoryStream();
__pictureBox.Image.Save(ms, ImageFormat.Png);
ms.Seek(0, SeekOrigin.Begin);
Image imag = Image.FromStream(ms);
// Derive BitMap object using Image instance, so that you can avoid the issue
//"a graphics object cannot be created from an image that has an indexed pixel format"
Bitmap img = new Bitmap(new Bitmap(imag));
SetClipboardData(img, hDC);
g.ReleaseHdc();
}
}
