C/C ++: how to load JPG images in a program?

Only the interfaces for loading BMP files by default are available for cwnd provided by MFC, which is not supported for jpg and other images. In reality, non-BMP images are often used and COM technology is required for loading them. First, write the following functions: Bool loadmydomainfile (cstring fname, lppicture * lppi) { Handle hfile = createfile (fname, generic_read, 0, null, open_existing, 0, null ); If (hfile = invalid_handle_value) { Cstring STR; Str. Format (_ T ("% s cannot be opened"), fname ); MessageBox (STR ); Return false; } // Obtain the file size DWORD dwfilesize = getfilesize (hfile, null ); If (DWORD)-1 = dwfilesize) { Closehandle (hfile ); MessageBox (_ T ("image file is empty ")); Return false; } // Read image files Lpvoid pvdata; // Allocate memory by file size Hglobal = globalalloc (gmem_moveable, dwfilesize ); If (null = hglobal) { Closehandle (hfile ); MessageBox (_ T ("insufficient memory, insufficient memory allocation ")); Return false; } Pvdata = globallock (hglobal ); If (null = pvdata) { Globalunlock (hglobal ); Closehandle (hfile ); MessageBox (_ T ("memory cannot be locked ")); Return false; } DWORD dwfileread = 0; Bool bread = readfile (hfile, pvdata, dwfilesize, & dwfileread, null ); Globalunlock (hglobal ); Closehandle (hfile ); If (false = bread) { MessageBox (_ T ("file read error ")); Return false; } Lpstream PSTM = NULL; // Generate an istream stream from the allocated memory Hresult hR = createstreamonhglobal (hglobal, true, & PSTM ); If (! Succeeded (HR )) { MessageBox (_ T ("failed to generate stream operation ")); If (PSTM! = NULL) PSTM-> release (); Return false; } Else if (PSTM = NULL) { MessageBox (_ T ("failed to generate stream operation ")); Return false; } If (! * Lppi) (* Lppi)-> release (); HR = oleloadpicture (PSTM, dwfilesize, false, iid_ipicture, (lpvoid *) & (* lppi )); PSTM-> release (); If (! Succeeded (HR )) { MessageBox (_ T ("loading failed ")); Return false; } Else if (* lppi = NULL) { MessageBox (_ T ("loading failed ")); Return false; } Return true; } Then add the variable declaration and function declaration to the header file: Bool loadmydomainfile (cstring fname, lppicture * lppi ); Lppicture m_lppi; // load the stream of the image file Bool m_bhadload; // The background image has been loaded. Then add the following to the onpaint function: If (m_bhadload) { CDC * PDC = getdc (); Crect RC; Long hmwidth = 0; Long hmheight = 0; M_lppi-> get_height (& hmheight ); M_lppi-> get_width (& hmwidth ); Getclientrect (& rc ); Int nwidth, nheight; Nwidth = RC. Width (); Nheight = RC. Height (); Hresult hR = m_lppi-> render (PDC-> m_hdc, nwidth, 0,-nwidth, nheight, Hmwidth, hmheight,-hmwidth,-hmheight, & rc ); } In the oninitdialog function, call the above loading function as follows: Tchar strpath [max_path]; Memset (strpath, 0, max_path ); Getcurrentdirectory (max_path, strpath ); Wcscat_s (strpath, max_path, _ T ("// a_bear.jpg ")); M_bhadload = loadmydomainfile (strpath, & m_lppi ); The jpg image can be displayed. Remember to add the following to the ondestroy function: M_lppi-> release (); To release objects.