There is an application called sabaki, under win10, run it later, it has a chessboard window, I use

HDC HDC=GetDC (HWND); Access to its window dc

Reoccupy BitBlt transferred to another image, then the image displayed, it was found that image completely black, empty,

CodePudding user response:

GetDC used during the WM_PAINT message, during the WM_PAINT message, use BenginPaint for DC

CodePudding user response:

It is said that DC is not cross thread!

CodePudding user response:

Try to copy the screen, and then capture part of the

 
BOOL CopyWnd (HWND hSrcWnd, HWND hDstWnd, BOOL bClientOnly) 
{
BOOL bRet=FALSE; 

HWND hDeskTop=NULL; 
HDC hSrcDC=NULL; 
HDC hMemDC=NULL; 
HBITMAP hMemBmp=NULL; 
HGDIOBJ hOldBmp=NULL; 
HDC hDstDC=NULL; 

Do 
{
HDeskTop=GetDesktopWindow ();//get handle to the desktop 

//handle to detect validity 
if(! (hDeskTop 
& & (hSrcWnd==NULL | | IsWindow (hSrcWnd)) 
& & IsWindow (hDstWnd) 
& & 1)) 
{
BRet=1; 
break; 
} 

//desktop DC 
HSrcDC=GetDC (hDeskTop); 
//Get Widht & amp; Height 
Int nWidth=GetDeviceCaps (hSrcDC HORZRES); 
Int nHeight=GetDeviceCaps (hSrcDC VERTRES); 

//create a memory DC 
HMemDC=CreateDC (_T (" DISPLAY "), NULL, NULL, NULL); 
If (hMemDC==NULL) 
{
BRet=2; 
break; 
} 

//create a memory bitmap 
HMemBmp=CreateBitmap (nWidth, nHeight, 1, 32, NULL); 
If (hMemBmp==NULL) 
{
BRet=3; 
break; 
} 
//for memory bitmap 
HOldBmp=SelectObject (hMemDC hMemBmp); 

/* 
if(! PrintWindow (hSrcWnd hMemDC, 0)) 
{
BRet=4; 
break; 
} 
*/
//copy the desktop DC 
if(! BitBlt (hSrcDC, 0, 0, nWidth, nHeight, hMemDC, 0, 0, SRCCOPY)) 
{
BRet=4; 
break; 
} 

//get map area coordinates 
The RECT rcSrc rcDst; 
If (hSrcWnd==NULL)//empty by default for the entire screen 
{
RcSrc. Left=rcSrc. Top=0; 
RcSrc. Right=nWidth, rcSrc. Bottom=nHeight; 
} 
Else if (bClientOnly) 
{
GetClientRect (hSrcWnd, & amp; RcSrc); 
POINT lt={rcSrc. Left, rcSrc. Top}; 
POINT rb={rcSrc. Right, rcSrc bottom}; 
ClientToScreen (hSrcWnd, & amp; Lt); 
ClientToScreen (hSrcWnd, & amp; Rb); 
RcSrc. Left=lt. X, rcSrc. Top=lt y; 
RcSrc. Right=rb. X, rcSrc. Bottom=rb. Y; 
} 
The else 
{
GetWindowRect (hSrcWnd, & amp; RcSrc); 
} 
GetClientRect (hDstWnd, & amp; RcDst); 

HDstDC=GetDC (hDstWnd); 
If (hDstDC==NULL) 
{
BRet=5; 
break; 
} 

//set the zoom halftone 
Int nOldMode=SetStretchBltMode (hDstDC, HALFTONE); 
//zoom the map 
StretchBlt (hDstDC, 
0, 0, rcDst. Right - rcDst. RcDst. Bottom - rcDst. Left, top, 
HMemDC, 
RcSrc left, rcSrc. Top rcSrc. Right - rcSrc. RcSrc. Bottom - rcSrc. Left, top, 
SRCCOPY); 
//restore zoom mode 
SetStretchBltMode (hDstDC nOldMode); 

BRet=TRUE; 

} while (0); 

//end cleanup 
If (hDstWnd & amp; & HDstDC) 
{
ReleaseDC (hDstWnd hDstDC); 
HDstDC=NULL; 
} 
If (hMemDC & amp; & HOldBmp) 
{
SelectObject (hMemDC hOldBmp); 
} 
If (hMemBmp) 
{
DeleteObject (hMemBmp); 
HMemBmp=NULL; 
} 
If (hMemDC) 
{
DeleteDC (hMemDC); 
HMemDC=NULL; 
} 
If (hDeskTop & amp; & HSrcDC) 
{
ReleaseDC (hDeskTop hSrcDC); 
HSrcDC=NULL; 
} 

Return bRet. 
} 

Void CDlg1Dlg: : OnButton1 () 
{
Cstrings szHwnd; 
GetDlgItemText (IDC_EDIT1 szHwnd); 
HWND hSrcWnd=(HWND) _ttoi64 (szHwnd);//window handle 
CopyWnd (hSrcWnd, GetDlgItem (IDC_STATIC1) - & gt; M_hWnd, 0); 
}