When using GDI to capture the window image and save it as BMP, the shadow around the window becomes black. Is there any way to solve it?

Question

RT, Or is there a way to get the width of the shadow, the width of the red box in the attachment screenshot？
beforce capture:

after capture:

capture desktop image:  
CreateCompatibleDC  
CreateCompatibleBitmap  
SelectObject  
  
capture window image:  
CreateCompatibleDC  
CreateCompatibleBitmap  
SelectObject  
  
compose window to desktop image:  
StretchBlt  

Answer 1

Try specifying ‘SRCCOPY | CAPTUREBLT’ in your BitBlt or StretchBlt calls.

If it does not help, then try calling DwmGetWindowAttribute(…, DWMWA_EXTENDED_FRAME_BOUNDS, …). It should return the rectangle without the black borders. Also use PhysicalToLogicalPointForPerMonitorDPI to convert the coordinates.

Check an example in C# that can be done in C++: https://learn.microsoft.com/en-us/answers/questions/522265/.