Create an in memory bitmap and draw directly to the memory - C++ WinAPI - Ответ 6989787

RECT gclientrect;
HDC gnewdc;
HBITMAP gnewbitmap;
int* gpnewbitmap;
 
void ResizeBitmap()
{
    if ((gnewdc != NULL) && (gclientrect.right != 0) && (gclientrect.bottom != 0))
    {
        BITMAPINFO lbitmapinfo;
        lbitmapinfo.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
        lbitmapinfo.bmiHeader.biWidth = gclientrect.right;
        lbitmapinfo.bmiHeader.biHeight = -gclientrect.bottom;
        lbitmapinfo.bmiHeader.biPlanes = 1;
        lbitmapinfo.bmiHeader.biBitCount = 32;
        lbitmapinfo.bmiHeader.biCompression = BI_RGB;
        lbitmapinfo.bmiHeader.biSizeImage = gclientrect.right * gclientrect.bottom * 4;
        lbitmapinfo.bmiHeader.biClrUsed = 0;
        lbitmapinfo.bmiHeader.biClrImportant = 0;
        if (gnewbitmap != NULL) DeleteObject(gnewbitmap);
        gnewbitmap = CreateDIBSection(gnewdc, &lbitmapinfo, DIB_RGB_COLORS, (void**)&gpnewbitmap, NULL, NULL);
        SelectObject(gnewdc, gnewbitmap);
    };
};
 
LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    int wmId, wmEvent;
    PAINTSTRUCT ps;
    HDC hdc;
 
    switch (message) 
    {
    case WM_SIZE:
        {
            GetClientRect(hWnd, &gclientrect);
            ResizeBitmap();
            break;
        };
    case WM_CREATE:
        {
            if (gnewdc == NULL)
            {
                HDC lhdc = GetDC(hWnd);
                gnewdc = CreateCompatibleDC(lhdc);
                ReleaseDC(hWnd, lhdc);
            };
            break;
        };
    case WM_ERASEBKGND:
        return 1;
    case WM_PAINT:
        hdc = BeginPaint(hWnd, &ps);
 
        if (gnewdc == NULL) gnewdc = CreateCompatibleDC(hdc);
 
        BitBlt(hdc,0,0,gclientrect.right,gclientrect.bottom,gnewdc,0,0,SRCCOPY);
        // TODO: Add any drawing code here...
        EndPaint(hWnd, &ps);
        break;
    case WM_DESTROY:
        PostQuitMessage(0);
        break;
    default:
        return DefWindowProc(hWnd, message, wParam, lParam);
    }
    return 0;
}