How can I load a bitmap inside my window? - winapi

Question

I'm trying to load a bitmap to a window I created. The bitmap should be the background of the window (I want to add labels on it an a progress bar later on).
This is my code:
HINSTANCE hInst;
LRESULT CALLBACK WindProcedure(HWND hWnd, UINT Msg, WPARAM wParam, LPARAM lParam);
INT WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
LPSTR lpCmdLine, int nCmdShow)
{
WNDCLASSEX WndCls;
static WCHAR szAppName[] = L"BitmapIntro";
MSG Msg;
hInst = hInstance;
WndCls.cbSize = sizeof(WndCls);
WndCls.style = CS_OWNDC | CS_VREDRAW | CS_HREDRAW;
WndCls.lpfnWndProc = WindProcedure;
WndCls.cbClsExtra = 0;
WndCls.cbWndExtra = 0;
WndCls.hInstance = hInst;
WndCls.hIcon = LoadIcon(NULL, IDI_APPLICATION);
WndCls.hCursor = LoadCursor(NULL, IDC_ARROW);
WndCls.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
WndCls.lpszMenuName = NULL;
WndCls.lpszClassName = szAppName;
WndCls.hIconSm = LoadIcon(hInstance, IDI_APPLICATION);
RegisterClassEx(&WndCls);
CreateWindowEx(WS_EX_OVERLAPPEDWINDOW,
szAppName,
L"Bitmaps Fundamentals",
WS_OVERLAPPEDWINDOW | WS_VISIBLE,
CW_USEDEFAULT,
CW_USEDEFAULT,
CW_USEDEFAULT,
CW_USEDEFAULT,
NULL,
NULL,
hInstance,
NULL);
while (GetMessage(&Msg, NULL, 0, 0))
{
TranslateMessage(&Msg);
DispatchMessage(&Msg);
}
return static_cast<int>(Msg.wParam);
}
LRESULT CALLBACK WindProcedure(HWND hWnd, UINT Msg, WPARAM wParam, LPARAM lParam)
{
HDC hDC, MemDCExercising;
PAINTSTRUCT Ps;
HBITMAP bmpExercising;
switch (Msg)
{
case WM_DESTROY:
PostQuitMessage(WM_QUIT);
break;
case WM_PAINT:
hDC = BeginPaint(hWnd, &Ps);
// Load the bitmap from the resource
bmpExercising = LoadBitmap(hInst, MAKEINTRESOURCE(IDB_BITMAP3));
// Create a memory device compatible with the above DC variable
MemDCExercising = CreateCompatibleDC(hDC);
// Select the new bitmap
SelectObject(MemDCExercising, bmpExercising);
// Copy the bits from the memory DC into the current dc
BitBlt(hDC, 10, 10, 450, 400, MemDCExercising, 0, 0, SRCCOPY);
// Restore the old bitmap
DeleteDC(MemDCExercising);
DeleteObject(bmpExercising);
EndPaint(hWnd, &Ps);
break;
default:
return DefWindowProc(hWnd, Msg, wParam, lParam);
}
return 0;
}
The problem is, the PNG size is small compared to the window, so when the PNG opens, it only occupies the left high corner. How can I make it stretch to my window size or at least draw it over and over until it fills the window?

Answer 1

How can I make it stretch to my window size
Use StretchBlt() instead of BitBlt().
case WM_PAINT:
{
// Get the window dimensions
RECT r;
GetClientRect(hWnd, &r);
// Load the bitmap from the resource
HBITMAP bmpExercising = LoadBitmap(hInst, MAKEINTRESOURCE(IDB_BITMAP3));
// Get the bitmap dimensions
BITMAP bmp;
GetObject(bmpExercising, sizeof(BITMAP), &bmp);
PAINTSTRUCT Ps;
HDC hDC = BeginPaint(hWnd, &Ps);
// Create a memory device compatible with the above DC variable
HDC MemDCExercising = CreateCompatibleDC(hDC);
// Select the new bitmap
HBITMAP hOldBmp = SelectObject(MemDCExercising, bmpExercising);
// Copy the bits from the memory DC into the current dc
StretchBlt(hDC, 0, 0, r.right - r.left, r.bottom - r.top, MemDCExercising, 0, 0, bmp.bmWidth, bmp.bmHeight, SRCCOPY);
// Restore the old bitmap
SelectObject(MemDCExercising, hOldBmp);
// Destroy the memory device
DeleteDC(MemDCExercising);
// Destroy the bitmap
DeleteObject(bmpExercising);
EndPaint(hWnd, &Ps);
break;
}
or at least draw it over and over until it fills the window?
There are two different ways to handle that.
at startup, load the bitmap and create an HBRUSH around it using CreatePatternBrush(), and then assign that to the WNDCLASS::hbrBackground field when you register your window class. Let the OS draw the window background using the bitmap for you.
HBITMAP bmpExercising = LoadBitmap(hInst, MAKEINTRESOURCE(IDB_BITMAP3));
WndCls.hbrBackground = CreatePatternBrush(bmpExercising);
if you want to paint the bitmap manually, have your paint handler call BitBlt() in a couple of loops. You know the dimensions of the bitmap (which you can retrieve in code using GetObject() and the BITMAP structure), and you know the dimensions of the window (which you can retrieve in code using GetWindowRect() or GetClientRect()). So simply draw the same bitmap more than one time at different offsets as needed. Start by drawing it once in the top-left corner, then move right bitmap-width pixels and draw it again, repeating until you move past window-width pixels. Then move left back to 0 and move down bitmap-height pixels and repeat the whole width-line again, repeating until you move past window-height pixels.
case WM_PAINT:
{
// Get the window dimensions
RECT r;
GetClientRect(hWnd, &r);
// Load the bitmap from the resource
HBITMAP bmpExercising = LoadBitmap(hInst, MAKEINTRESOURCE(IDB_BITMAP3));
// Get the bitmap dimensions
BITMAP bmp;
GetObject(bmpExercising, sizeof(BITMAP), &bmp);
PAINTSTRUCT Ps;
HDC hDC = BeginPaint(hWnd, &Ps);
// Create a memory device compatible with the above DC variable
HDC MemDCExercising = CreateCompatibleDC(hDC);
// Select the new bitmap
HBITMAP hOldBmp = SelectObject(MemDCExercising, bmpExercising);
int width = r.right - r.left;
int height = r.bottom - r.top;
// Copy the bits from the memory DC into the current dc
for(int y = 0; y < height; y += bmp.bmHeight)
{
for(int x = 0; x < width; x += bmp.bmWidth)
{
BitBlt(hDC, x, y, bmp.bmWidth, bmp.bmHeight, MemDCExercising, 0, 0, SRCCOPY);
}
}
// Restore the old bitmap
SelectObject(MemDCExercising, hOldBmp);
// Destroy the memory device
DeleteDC(MemDCExercising);
// Destroy the bitmap
DeleteObject(bmpExercising);
EndPaint(hWnd, &Ps);
break;
}
Now, with that said, here are some additional notes:
you should not be loading the bitmap inside of your paint handler. Load it one time before creating the window, and then reuse the same HBITMAP for each paint operation until the window is destroyed, then free the bitmap.
LoadBitmap() is deprecated, you should be using LoadImage() instead, eg:
HBITMAP bmpExercising = (HBITMAP) LoadImage(hInst, MAKEINTRESOURCE(IDB_BITMAP3), IMAGE_BITMAP, 0, 0, LR_CREATEDIBSECTION);
you said "The bitmap should be the background of the window", so you should be drawing the bitmap in response to the WM_ERASEBKGND message instead of the WM_PAINT message.
case WM_ERASEBKGND:
{
HDC hDC = (HDC) wParam;
// draw the bitmap on hDC as needed...
return 1;
}