I have created a simple win32 application to open the dialog from menu, select the bitmap image and display or paint it on window. Now the problem I am facing is that when I get the filename from GetOpenFileName method and pass it to LoadImage function, the image couldn't be loaded. But if I pass the file path "D:/Splash.bmp" directly into the function parameter, the image is loaded. The problem is that GetOpenFileName method gives "D:\Splash.bmp" as path while the program is working with "D:/Splash.bmp". What could be the error?
Here is the code:
//Win32Bitmap.cpp : Defines the entry point for the application.//
#include "stdafx.h"
#include "Win32Bitmap.h"
#include<Windows.h>
#include <Commdlg.h>
#define MAX_LOADSTRING 100
// Global Variables:
HINSTANCE hInst; // current instance
TCHAR szTitle[MAX_LOADSTRING]; // The title bar text
TCHAR szWindowClass[MAX_LOADSTRING]; // the main window class name
// Forward declarations of functions included in this code module:
ATOM MyRegisterClass(HINSTANCE hInstance);
BOOL InitInstance(HINSTANCE, int);
LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
INT_PTR CALLBACK About(HWND, UINT, WPARAM, LPARAM);
int APIENTRY _tWinMain(_In_ HINSTANCE hInstance,
_In_opt_ HINSTANCE hPrevInstance,
_In_ LPTSTR lpCmdLine,
_In_ int nCmdShow)
{
UNREFERENCED_PARAMETER(hPrevInstance);
UNREFERENCED_PARAMETER(lpCmdLine);
// TODO: Place code here.
MSG msg;
HACCEL hAccelTable;
// Initialize global strings
LoadString(hInstance, IDS_APP_TITLE, szTitle, MAX_LOADSTRING);
LoadString(hInstance, IDC_WIN32BITMAP, szWindowClass, MAX_LOADSTRING);
MyRegisterClass(hInstance);
// Perform application initialization:
if (!InitInstance (hInstance, nCmdShow))
{
return FALSE;
}
hAccelTable = LoadAccelerators(hInstance, MAKEINTRESOURCE(IDC_WIN32BITMAP));
// Main message loop:
while (GetMessage(&msg, NULL, 0, 0))
{
if (!TranslateAccelerator(msg.hwnd, hAccelTable, &msg))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
}
return (int) msg.wParam;
}
//
// FUNCTION: MyRegisterClass()
//
// PURPOSE: Registers the window class.
//
ATOM MyRegisterClass(HINSTANCE hInstance)
{
WNDCLASSEX wcex;
wcex.cbSize = sizeof(WNDCLASSEX);
wcex.style = CS_HREDRAW | CS_VREDRAW;
wcex.lpfnWndProc = WndProc;
wcex.cbClsExtra = 0;
wcex.cbWndExtra = 0;
wcex.hInstance = hInstance;
wcex.hIcon = LoadIcon(hInstance, MAKEINTRESOURCE(IDI_WIN32BITMAP));
wcex.hCursor = LoadCursor(NULL, IDC_ARROW);
wcex.hbrBackground = (HBRUSH)(COLOR_WINDOW+1);
wcex.lpszMenuName = MAKEINTRESOURCE(IDC_WIN32BITMAP);
wcex.lpszClassName = szWindowClass;
wcex.hIconSm = LoadIcon(wcex.hInstance, MAKEINTRESOURCE(IDI_SMALL));
return RegisterClassEx(&wcex);
}
//
// FUNCTION: InitInstance(HINSTANCE, int)
//
// PURPOSE: Saves instance handle and creates main window
//
// COMMENTS:
//
// In this function, we save the instance handle in a global variable and
// create and display the main program window.
//
BOOL InitInstance(HINSTANCE hInstance, int nCmdShow)
{
HWND hWnd;
hInst = hInstance; // Store instance handle in our global variable
hWnd = CreateWindow(szWindowClass, szTitle, WS_OVERLAPPEDWINDOW,
CW_USEDEFAULT, 0, CW_USEDEFAULT, 0, NULL, NULL, hInstance, NULL);
if (!hWnd)
{
return FALSE;
}
ShowWindow(hWnd, nCmdShow);
UpdateWindow(hWnd);
return TRUE;
}
bool LoadAndBlitBitmap(LPTSTR szFileName, HDC hdcWin)
{
HBITMAP hbitmap;
hbitmap = (HBITMAP)LoadImage(NULL, szFileName, IMAGE_BITMAP, 0, 0, LR_LOADFROMFILE);
if (hbitmap == NULL)
{
MessageBox(NULL, L"Image couldn't be loaded", L"Error", MB_OK | MB_ICONEXCLAMATION);
return false;
}
//create a memory device context that is compatible with the window
HDC hdclocal = CreateCompatibleDC(hdcWin);
if (hdclocal == NULL)
{
MessageBox(NULL, L"device context not created", L"Error", MB_OK | MB_ICONEXCLAMATION);
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"Get object failed", L"Error", MB_OK | MB_ICONEXCLAMATION);
return false;
}
//select the loaded bitmap into the device context
HBITMAP holdbitmap = (HBITMAP)SelectObject(hdclocal, hbitmap);
if (holdbitmap==NULL)
{
MessageBox(NULL, L"Get object failed", L"Error", MB_OK | MB_ICONEXCLAMATION);
return false;
}
//transfer the device context from the memory device context to the windows context(actual drawing surface)
bool qRetBlit = BitBlt(hdcWin, 0, 0, qbitmap.bmWidth, qbitmap.bmHeight, hdclocal, 0, 0, SRCCOPY);
if (!qRetBlit)
{
MessageBox(NULL, L"bitblt failed", L"Error", MB_OK | MB_ICONEXCLAMATION);
return false;
}
//deallocate the resources
SelectObject(hdclocal, holdbitmap);
DeleteDC(hdclocal);
DeleteObject(hbitmap);
return true;
}
//
// FUNCTION: WndProc(HWND, UINT, WPARAM, LPARAM)
//
// PURPOSE: Processes messages for the main window.
//
// WM_COMMAND - process the application menu
// WM_PAINT - Paint the main window
// WM_DESTROY - post a quit message and return
//
//
LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
int wmId, wmEvent;
PAINTSTRUCT ps;
HDC hdc;
wchar_t szFileName[MAX_PATH] = L"";
switch (message)
{
case WM_COMMAND:
wmId = LOWORD(wParam);
wmEvent = HIWORD(wParam);
// Parse the menu selections:
switch (wmId)
{
case IDM_ABOUT:
DialogBox(hInst, MAKEINTRESOURCE(IDD_ABOUTBOX), hWnd, About);
break;
case IDM_EXIT:
DestroyWindow(hWnd);
break;
case ID_FILE_OPEN:
{
OPENFILENAME ofn;
ZeroMemory(&ofn, sizeof(ofn));
ofn.lStructSize = sizeof(ofn); // SEE NOTE BELOW
ofn.hwndOwner = hWnd;
ofn.lpstrFilter = L"Bitmap Files (*.bmp)\0*.bmp\0All Files (*.*)\0*.*\0";
ofn.lpstrFile = szFileName;
ofn.nMaxFile = MAX_PATH;
ofn.Flags = OFN_EXPLORER | OFN_FILEMUSTEXIST | OFN_HIDEREADONLY;
ofn.lpstrDefExt = L"bmp";
if (GetOpenFileName(&ofn))
{
MessageBox(NULL, szFileName, L"path", MB_OK);
//InvalidateRect(hWnd, 0, TRUE);
}
}
break;
default:
return DefWindowProc(hWnd, message, wParam, lParam);
}
break;
case WM_PAINT:
hdc = BeginPaint(hWnd, &ps);
// TODO: Add any drawing code here...
LoadAndBlitBitmap(L"D:/Splash.bmp", hdc);
EndPaint(hWnd, &ps);
break;
case WM_DESTROY:
PostQuitMessage(0);
break;
default:
return DefWindowProc(hWnd, message, wParam, lParam);
}
return 0;
}
// Message handler for about box.
INT_PTR CALLBACK About(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam)
{
UNREFERENCED_PARAMETER(lParam);
switch (message)
{
case WM_INITDIALOG:
return (INT_PTR)TRUE;
case WM_COMMAND:
if (LOWORD(wParam) == IDOK || LOWORD(wParam) == IDCANCEL)
{
EndDialog(hDlg, LOWORD(wParam));
return (INT_PTR)TRUE;
}
break;
}
return (INT_PTR)FALSE;
}
The backslash is not the problem. In fact, windows prefers backslash over forward slash. Your problem is the fact that you have made your szFileName buffer local to window procedure function (WndProc). When you click menu item to select a file, message WM_COMMAND is sent to the window and handled by this its window procedure. You have correctly implemented opening of dialog and retrieving the file path. However, when this handling is complete, function WndProc exits and destroys all local variables from the stack, including the file path contained in szFileName.
To fix your problem, make szFileName a global variable so it does not get destroyed. Also note that the window will not update itself automatically after you select the image file, you need to instruct the window to repaint itself by adding this code after the call to GetOpenFileName:
InvalidateRect(hWnd, NULL, TRUE);
UpdateWindow(hWnd);
This will invalidate the entire window region and schedule a repainting of window (this means that message WM_PAINT will again be sent to the window and handled by WndProc).