将窗口内容显示为位图

Question

i want to take a image of window's content and show it as smaller bitmap in that window... i followed this article: http://msdn.microsoft.com/en-us/library/dd183402(v=vs.85).aspx and when i want take screenshot of whole desktop - it works fine... problem is when i try to get bitmap only of window's content. Any ideas what am I doing wrong ?

Here's my code:

HDC hDC;
HDC hDCMemDC = NULL;
HBITMAP hbmWindow = NULL;
BITMAP bmpWindow;

hDC = GetDC(hWnd);

hDCMemDC = CreateCompatibleDC(hDC);

RECT clientRect;
GetClientRect(hWnd, &clientRect);

hbmWindow = CreateCompatibleBitmap(hDC, clientRect.right - clientRect.left, clientRect.bottom - clientRect.top);

SelectObject(hDCMemDC, hbmWindow);

BitBlt(hDCMemDC, 0, 0, 100, 100, hDC, 0, 0, SRCCOPY);

Thanks

Answer 1

void DrawSelf(HDC Context, RECT Area, RECT NewArea)
{
    uint32_t W = Area.right - Area.left;
    uint32_t H = Area.bottom - Area.top;
    uint32_t NW = NewArea.right - NewArea.left;
    uint32_t NH = NewArea.bottom - NewArea.top;

    StretchBlt(Context, NewArea.left, NewArea.top, NW, NH, Context, Area.left, Area.top, W, H, SRCCOPY);
}

Then you can do:

RECT Area;
RECT Area2;
HDC DC = GetDC(hwnd);  //Gets the client area only.. Use GetWindowDC for the whole window including the title-bar.
GetClientRect(hwnd, &Area); //client area only.
GetClientRect(hwnd, &Area2);

//Smaller area in which to draw.
Area2.left += 5;
Area2.right -= 5;
Area2.top += 5;
Area2.bottom -= 5;


DrawSelf(DC, Area, Area2);

ReleaseDC(hwnd, dc);

Answer 2

使用GetWindowDC而不是GetDC来获取整个窗口区域。