Unable to load multiple bitmaps - WinAPI [duplicate] - c++

Question

This question already has answers here:
How to get list of selected files when using GetOpenFileName() with multiselect flag?
(5 answers)
Closed 5 years ago.
So recently I have been able to get my application to allow the user to load .bmp files from external directories. The application loads the picture just fine, but if the user highlights multiple pictures, my LoadImage() function complains and I think it's because it's getting multiple files at once so it doesn't know how to read them properly. (maybe).
Here's my Init function
void InitialiseDialog(HWND hwnd)
{
ZeroMemory(&ofn, sizeof(ofn));
ofn.lStructSize = sizeof(OPENFILENAME);
ofn.hInstance = GetModuleHandle(NULL);
ofn.lpstrCustomFilter = NULL;
ofn.nMaxCustFilter = 0;
ofn.nFilterIndex = 0;
ofn.nMaxFile = MAX_PATH;
ofn.hwndOwner = hwnd;
ofn.lpstrFile = file;
ofn.lpstrFilter = TEXT("Bitmap Files (*.bmp)\0*.bmp\0\0");
ofn.lpstrFileTitle = NULL;
ofn.nMaxFileTitle = MAX_PATH;
ofn.lpstrInitialDir = NULL;
ofn.lpstrTitle = NULL;
ofn.Flags = OFN_EXPLORER | OFN_FILEMUSTEXIST | OFN_PATHMUSTEXIST | OFN_ALLOWMULTISELECT;
ofn.nFileOffset = 0;
ofn.nFileExtension = 0;
ofn.lpstrDefExt = NULL;
ofn.lCustData = 0L;
ofn.lpfnHook = NULL;
ofn.lpTemplateName = NULL;
}
And here's how I'm loading bitmaps and calling things:
bool LoadAndBlitBitmap(LPCWSTR myFile, HDC hWinDC)
{
// Load the bitmap image file
hBitmap = (HBITMAP)::LoadImage(NULL, myFile, IMAGE_BITMAP, 0, 0, LR_LOADFROMFILE);
// Verify that the image was loaded
if (hBitmap == NULL) {
::MessageBox(NULL, L"LoadImage Failed", L"Error", MB_OK);
return false;
}
// Create a device context that is compatible with the window
HDC hLocalDC;
hLocalDC = ::CreateCompatibleDC(hWinDC);
// Verify that the device context was created
if (hLocalDC == NULL) {
::MessageBox(NULL, L"CreateCompatibleDC Failed", L"Error", MB_OK);
return false;
}
// Get the bitmap's parameters and verify the get
BITMAP qBitmap;
int iReturn = GetObject(reinterpret_cast<HGDIOBJ>(hBitmap), sizeof(BITMAP),
reinterpret_cast<LPVOID>(&qBitmap));
if (!iReturn) {
::MessageBox(NULL, L"GetObject Failed", L"Error", MB_OK);
return false;
}
// Select the loaded bitmap into the device context
HBITMAP hOldBmp = (HBITMAP)::SelectObject(hLocalDC, hBitmap);
if (hOldBmp == NULL) {
::MessageBox(NULL, L"SelectObject Failed", L"Error", MB_OK);
return false;
}
// Blit the dc which holds the bitmap onto the window's dc
BOOL qRetBlit = ::BitBlt(hWinDC, 0, 0, qBitmap.bmWidth, qBitmap.bmHeight,
hLocalDC, 0, 0, SRCCOPY);
if (!qRetBlit) {
::MessageBox(NULL, L"Blit Failed", L"Error", MB_OK);
return false;
}
// Unitialize and deallocate resources
::SelectObject(hLocalDC, hOldBmp);
::DeleteDC(hLocalDC);
::DeleteObject(hBitmap);
return true;
}
LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
int wmId, wmEvent;
PAINTSTRUCT ps;
switch (message)
{
case WM_CREATE:
InitialiseDialog(hWnd);
return 0;
case WM_COMMAND:
wmId = LOWORD(wParam);
wmEvent = HIWORD(wParam);
// Parse the menu selections:
switch (wmId)
{
case ID_FILE_LOADIMAGES:
if (GetOpenFileName(&ofn))
{
g_bhBitmap = !g_bhBitmap;
}
InvalidateRect(hWnd, NULL, TRUE);
return 0;
break;
case ID_FILE_LOADAUDIO:
DestroyWindow(hWnd);
break;
case ID_FILE_EXIT:
DestroyWindow(hWnd);
break;
default:
return DefWindowProc(hWnd, message, wParam, lParam);
}
case WM_PAINT:
hdc = BeginPaint(hWnd, &ps);
if (g_bhBitmap)
{
LoadAndBlitBitmap(file, hdc); // <-- Something not right about this...?
}
EndPaint(hWnd, &ps);
break;
case WM_DESTROY:
The Output1 (<-- Link does not open new tab so right-click and open new tab if you want to see the output, it's really just an error message...)
Thank you for reading my query. I'd greatly appreciate any help you could give me :) bye.
EDIT: Here are some variable definitions:
// Global Variables
HINSTANCE g_hInst;
HBITMAP hBitmap;
HDC hdc;
static OPENFILENAME ofn;
bool g_bhBitmap = false;
wchar_t file[1024];

Answer 1

My first suggestion would be to remove OFN_ALLOWMULTISELECT from the flags.
If you keep it, you need to handle the case of the user selecting multiple files correctly.
From the manual:
OFN_ALLOWMULTISELECT
The File Name list box allows multiple selections.
If the user selects more than one file, the lpstrFile buffer returns
the path to the current directory followed by the file names of the
selected files.
The nFileOffset member is the offset, in bytes or characters, to the
first file name, and the nFileExtension member is not used.
The directory and file name strings are NULL separated, with an extra
NULL character after the last file name.
When you send that to
hBitmap = (HBITMAP)::LoadImage(NULL, myFile, IMAGE_BITMAP, 0, 0, LR_LOADFROMFILE);
you are essentially trying to load a directory as a bitmap. Instead, you need to individually create finenames for each selection, and load those separatly.