Q: (.NET/GDI/BitBlt) Problem copying form to bitmap

[=?Utf-8?B?Y3JhbmtlX2JveQ==?=]

Hi Folks,

I'm not sure where this post belongs since I'm using managed vc.net, but the
issue is around GDI BitBlt.

Here is a summary of the problem:
- I am trying to copy a bitmap of my main form into a picture box.
- To do this, I bitblt using the device contexts of the form and a bitmap
object.
- After blitting, the bitmap image is always blank. I don't understand what
I'm doing wrong here.

Here is my relevant code:

MainMenuForm_Sh own(...)
{
Graphics ^formGraphics = this->CreateGraphics ();
Bitmap ^bitmap = gcnew Bitmap(this->Width, this->Height, formGraphics);
Graphics ^bitmapGraphics = Graphics::FromI mage(bitmap);
IntPtr formDC = formGraphics->GetHdc();
IntPtr bitmapDC = bitmapGraphics->GetHdc();

BitBlt(bitmapDC , 0, 0, this->Width, this->Height, formDC, 0, 0, 0xCC0020);

formGraphics->ReleaseHdc(for mDC);
bitmapGraphics->ReleaseHdc(bit mapDC);

bitmap->Save(CCarthage Defs::DIR_IMAGE S + "test.jpg") ;
}

After running the above code, the file test.jpg is tiny and basically blank
(maybe all solid grayish white). I expected it to be a copy of the form.
Any comments on why this is happening would be most appreciated.

I thought maybe the problem was with the form, so I tried an even simpler
test: copying one image to another. Here is the code:
Bitmap ^srcImage = gcnew Bitmap("input.j pg");
Graphics ^srcG = Graphics::FromI mage(srcImage);
Bitmap ^toImage = gcnew Bitmap(srcImage->Width, srcImage->Height,
srcG);
Graphics ^toG = Graphics::FromI mage(toImage);

IntPtr srcDc = srcG->GetHdc();
IntPtr toDc = toG->GetHdc();

BitBlt(toDc, 0, 0, srcImage->Width, srcImage->Height, srcDc, 0, 0,
0xCC0020);

srcG->ReleaseHdc(src Dc);
toG->ReleaseHdc(toD c);

srcImage->Save(CCarthage Defs::DIR_IMAGE S + "test1.jpg" );
toImage->Save(CCarthage Defs::DIR_IMAGE S + "test2.jpg" );
---
After running the above code, test1.jpg (an output of the source image) is a
correct copy of the source image. test2.jpg is *blank*?? Again, something
with the BitBlt seems to have failed ...

Also, to make sure I was actually hitting the genuine BitBlt code, I tried
using the options BLACKNESS and WHITENESS. Both worked ... the destination
turned the appropriate color.

Finally, in case anyone is interested in why I'm doing this ... I am having
some ugly flicker at the load-up of my form. I'm trying to take a copy of
the form's look, put it in a screen-sized picture box, and display that to
the user before they see the real form.

Thanks

[=?Utf-8?B?Y3JhbmtlX2JveQ==?=]

I thought the following might also be helpful:
- I tried to use control->DrawToBitmap() . but it doesn't draw all the
sub-controls that I need it to.
- I am using VC++ under Visual Studio Express 2008.
- Here is my prototype for BitBlt:
[System::Runtime ::InteropServic es::DllImportAt tribute("gdi32. dll")]
extern bool BitBlt(IntPtr hDestDC,
int x,
int y,
int nWidth,
int nHeight,
IntPtr hSrcDC,
int xSrc,
int ySrc,
int dwRop);