6 replies to this topic

[johnnyBravo]

Hi, how would I save a HDC to a bitmap? ..its to take screenshots thx

[kuphryn]

CreateDIBSection()
StretchBlt()

Kuphryn

[yadango]

Here, you can have my code. Though there may have to be some
changes done to it as it is like written way back for Win32s.
For Direct3D however, you might need to use the surface data,
because of hardware acceleration, GDI caps more than likely
won't work. There is also another way to do this by sending
the WM_PRINT message.

void CaptureScreen(HWND window, const char* filename)
{
 // get screen rectangle
 RECT windowRect;
 GetWindowRect(window, &windowRect);

 // bitmap dimensions
 int bitmap_dx = windowRect.right - windowRect.left;
 int bitmap_dy = windowRect.bottom - windowRect.top;

 // create file
 ofstream file(filename, ios::binary);
 if(!file) return;

 // save bitmap file headers
 BITMAPFILEHEADER fileHeader;
 BITMAPINFOHEADER infoHeader;

 fileHeader.bfType      = 0x4d42;
 fileHeader.bfSize      = 0;
 fileHeader.bfReserved1 = 0;
 fileHeader.bfReserved2 = 0;
 fileHeader.bfOffBits   = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);

 infoHeader.biSize          = sizeof(infoHeader);
 infoHeader.biWidth         = bitmap_dx;
 infoHeader.biHeight        = bitmap_dy;
 infoHeader.biPlanes        = 1;
 infoHeader.biBitCount      = 24;
 infoHeader.biCompression   = BI_RGB;
 infoHeader.biSizeImage     = 0;
 infoHeader.biXPelsPerMeter = 0;
 infoHeader.biYPelsPerMeter = 0;
 infoHeader.biClrUsed       = 0;
 infoHeader.biClrImportant  = 0;

 file.write((char*)&fileHeader, sizeof(fileHeader));
 file.write((char*)&infoHeader, sizeof(infoHeader));

 // dibsection information
 BITMAPINFO info;
 info.bmiHeader = infoHeader; 

 // ------------------
 // THE IMPORTANT CODE
 // ------------------
 // create a dibsection and blit the window contents to the bitmap
 HDC winDC = GetWindowDC(window);
 HDC memDC = CreateCompatibleDC(winDC);
 BYTE* memory = 0;
 HBITMAP bitmap = CreateDIBSection(winDC, &info, DIB_RGB_COLORS, (void**)&memory, 0, 0);
 SelectObject(memDC, bitmap);
 BitBlt(memDC, 0, 0, bitmap_dx, bitmap_dy, winDC, 0, 0, SRCCOPY);
 DeleteDC(memDC);
 ReleaseDC(window, winDC);

 // save dibsection data
 int bytes = (((24*bitmap_dx + 31) & (~31))/8)*bitmap_dy;
 file.write(memory, bytes);

 // HA HA, forgot paste in the DeleteObject lol, happy now ;)?
 DeleteObject(bitmap);
}

[Edited by - yadango on May 27, 2006 12:16:53 AM]

[yadango]

good eye. forgot to add DeleteObject ha ha ha.

[johnnyBravo]

if I use this instead:
HDC winDC = CreateDC("DISPLAY", 0,0,0);

do i just delete it: DeleteDC(winDC); ?

Also is there a way to capture the pixels from videos playing aswell. I know that they are playing on a different layer, but isn't there some higher level function of getting the pixels onscreen?