本文共 3815 字,大约阅读时间需要 12 分钟。
1.是MFC工程
2.创建默认工程:单文档工程
3.工程名:JPEGTest
4.1在CJPEGTestView类中添加
HANDLE
m_hFile; CImage m_Image; void LoadMemImage( void * pMemData, long len); afx_msg void OnFileOpen(); 4.2在stdafx.h中添加#include <atlimage.h> 4.3在CJPEGTestView.cpp中添加 BEGIN_MESSAGE_MAP(CJPEGTestView, CView) ON_COMMAND(ID_FILE_OPEN, &CJPEGTestView::OnFileOpen)//这个是添加的 END_MESSAGE_MAP() 4.4 void CJPEGTestView::OnFileOpen() { CString strFilter; CSimpleArray<GUID> aguidFileTypes; HRESULT hResult; // 获取CImage支持的图像文件的过滤字符串 hResult = m_Image.GetExporterFilterString(strFilter,aguidFileTypes, _T( "All Image Files") ); if ( FAILED(hResult) ) { MessageBox(_T("GetExporterFilter调用失败!")); return; } CFileDialog dlg( TRUE, NULL, NULL, OFN_FILEMUSTEXIST, strFilter ); if ( IDOK != dlg.DoModal() ) return; m_Image.Destroy(); { //在此处是用流的方式显示JPEG m_hFile = ::CreateFile(dlg.GetFileName(),GENERIC_READ,0,NULL,OPEN_EXISTING, FILE_ATTRIBUTE_READONLY,NULL); // 用这个函数比OpenFile好 if ( m_hFile == INVALID_HANDLE_VALUE) { MessageBox(_T("打开文件失败")); CloseHandle( m_hFile ); // 一定注意在函数退出之前对句柄进行释放。 return; } DWORD filesize=GetFileSize( m_hFile,NULL ); char* buffer=new char[filesize+1]; // 最后一位为 '/0',C-Style 字符串的结束符。 DWORD readsize; ReadFile( m_hFile,buffer,filesize,&readsize,NULL); buffer[filesize]=0; LoadMemImage(buffer,readsize); delete[] buffer; // 注意是delete[] 而不是 delete CloseHandle(m_hFile); // 关闭句柄。 } // 设置主窗口标题栏内容 CString str; str.LoadString(AFX_IDS_APP_TITLE); AfxGetMainWnd()->SetWindowText(str + _T("_") + dlg.GetFileName()); Invalidate(); // 强制调用OnDraw } void CJPEGTestView::LoadMemImage( void * pMemData, long len) { HGLOBAL hGlobal = GlobalAlloc(GMEM_MOVEABLE, len); void * pData = GlobalLock(hGlobal); memcpy(pData, pMemData, len); GlobalUnlock(hGlobal); IStream * pStream = NULL; if (CreateStreamOnHGlobal(hGlobal, TRUE, & pStream) == S_OK) { if ( FAILED( m_Image.Load(pStream)) ) { MessageBox(_T("调用图像文件失败!")); return; } pStream -> Release(); } GlobalFree(hGlobal); } void CJPEGTestView::OnDraw(CDC* pDC) { CJPEGTestDoc* pDoc = GetDocument(); ASSERT_VALID(pDoc); if (!m_Image.IsNull()) { m_Image.Draw(pDC->m_hDC,0,0); } } 5.还可以添加放大缩小功能 在:CJPEGTestDoc类中添加: public: inline float GetZoomFactor() { return m_ZoomFactor; } protected: float m_ZoomFactor;//在构造函数中初始化1.00 BEGIN_MESSAGE_MAP(CJPEGTestDoc, CDocument) ON_COMMAND(AFX_ID_PREVIEW_ZOOMOUT, OnViewZoomout) ON_COMMAND(AFX_ID_PREVIEW_ZOOMIN, OnViewZoomin) END_MESSAGE_MAP() void CJPEGTestDoc::OnViewZoomout() { if (m_ZoomFactor<=0.0625) return; if (m_ZoomFactor == 2.00f) m_ZoomFactor = 1.50f; else if (m_ZoomFactor == 1.50f) m_ZoomFactor = 1.00f; else if (m_ZoomFactor == 1.00f) m_ZoomFactor = 0.75f; else if (m_ZoomFactor == 0.75f) m_ZoomFactor = 0.50f; else m_ZoomFactor/=2; CStatusBar& statusBar = ((CMainFrame *)(AfxGetApp()->m_pMainWnd))->GetStatusBar(); CString s; s.Format(_T("%4.1f %%"),m_ZoomFactor*100); statusBar.SetPaneText(2, s); UpdateAllViews(NULL,WM_USER_NEWIMAGE); } void CJPEGTestDoc::OnViewZoomin() { if (m_ZoomFactor>=16) return; if (m_ZoomFactor == 0.50f) m_ZoomFactor = 0.75f; else if (m_ZoomFactor == 0.75f) m_ZoomFactor = 1.00f; else if (m_ZoomFactor == 1.00f) m_ZoomFactor = 1.50f; else if (m_ZoomFactor == 1.50f) m_ZoomFactor = 2.00f; else m_ZoomFactor*=2; CStatusBar& statusBar = ((CMainFrame *)(AfxGetApp()->m_pMainWnd))->GetStatusBar(); CString s; s.Format(_T("%4.0f %%"),m_ZoomFactor*100); statusBar.SetPaneText(2, s); UpdateAllViews(NULL,WM_USER_NEWIMAGE); } 6.显示的时候,做相应的更改 void CJPEGTestView::OnDraw(CDC* pDC) { CJPEGTestDoc* pDoc = GetDocument(); ASSERT_VALID(pDoc); if (!m_Image.IsNull()) { float zoom=pDoc->GetZoomFactor(); if (zoom==1) m_Image.Draw(pDC->m_hDC,0,0); else { pDC->SetStretchBltMode( HALFTONE ); //防止缩小图片失真 m_Image.Draw(pDC->GetSafeHdc(),CRect(0,0,(int)(m_Image.GetWidth()*zoom),(int)(m_Image.GetHeight()*zoom))); } } } 差不多了。就这些,也是从网上看了相关的资料后,自己动手实验一下。
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