至顶网›软件频道 ›基础软件›在MFC应用程序中显示JPG/GIF图像文件

在MFC应用程序中显示JPG/GIF图像文件

扫一扫
分享文章到微信
扫一扫
关注官方公众号
至顶头条

如果你是一个使用Visual Basic编程的程序员，要在程序中显示JPG或者GIF图像简直易如反掌，将图像控件拖到Form中就可以了。

作者：刘涛来源：天极开发 2007年10月16日

关键字：

三、程序代码

/////////////////// Picture object--encapsulates IPicture
#pragma once
#include <atlbase.h>
class CPicture {
public:
CPicture();
~CPicture();
// Load frm various sosurces
BOOL Load(UINT nIDRes);
BOOL Load(LPCTSTR pszPathName);
BOOL Load(CFile& file);
BOOL Load(CArchive& ar);
BOOL Load(IStream* pstm);
// render to device context
BOOL Render(CDC* pDC, CRect rc=CRect(0,0,0,0),
LPCRECT prcMFBounds=NULL) const;
CSize GetImageSize(CDC* pDC=NULL) const;
operator IPicture*() {
　return m_spIPicture;
}
void GetHIMETRICSize(OLE_XSIZE_HIMETRIC& cx, OLE_YSIZE_HIMETRIC& cy) const
{
　cx = cy = 0;
　const_cast<CPicture*>(this)->m_hr = m_spIPicture->get_Width(&cx);
　ASSERT(SUCCEEDED(m_hr));
　const_cast<CPicture*>(this)->m_hr = m_spIPicture->get_Height(&cy);
　ASSERT(SUCCEEDED(m_hr));
}

void Free()
{
　if (m_spIPicture) {
　　m_spIPicture.Release();
　}
}

protected:
CComQIPtr<IPicture>m_spIPicture; // ATL smart pointer to IPicture
HRESULT m_hr; // last error code
};

/////////////////////////////////////////////////////////////// CPicture implementation
#include "StdAfx.h"
#include "Picture.h"
#ifdef _DEBUG
#define new DEBUG_NEW
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif

CPicture::CPicture()
{}

CPicture::~CPicture()
{}

BOOL CPicture::Load(UINT nIDRes) // Load from resource. Looks for "IMAGE" type.
{
　// find resource in resource file
　HINSTANCE hInst = AfxGetResourceHandle();
　HRSRC hRsrc = ::FindResource(hInst,MAKEINTRESOURCE(nIDRes),"IMAGE"); // type
　if (!hRsrc)
　　return FALSE;
　// load resource into memory
　DWORD len = SizeofResource(hInst, hRsrc);
　BYTE* lpRsrc = (BYTE*)LoadResource(hInst, hRsrc);
　if (!lpRsrc)
　　return FALSE;
　// create memory file and load it
　CMemFile file(lpRsrc, len);
　BOOL bRet = Load(file);
　FreeResource(hRsrc);
　GlobalFree(lpRsrc);
　return bRet;
}

BOOL CPicture::Load(LPCTSTR pszPathName) // Load from path name.
{
　CFile file;
　if (!file.Open(pszPathName, CFile::modeRead|CFile::shareDenyWrite))
　　return FALSE;
　BOOL bRet = Load(file);
　file.Close();
　return bRet;
}

BOOL CPicture::Load(CFile& file) // Load from CFile
{
　CArchive ar(&file, CArchive::load | CArchive::bNoFlushOnDelete);
　return Load(ar);
}

////// Load from archive--create stream and load from stream.
BOOL CPicture::Load(CArchive& ar)
{
　CArchiveStream arcstream(&ar);
　return Load((IStream*)&arcstream);
}

//////////////////
// Load from stream (IStream). This is the one that really does it: call
// OleLoadPicture to do the work.
BOOL CPicture::Load(IStream* pstm)
{
　Free();
　HRESULT hr = OleLoadPicture(pstm, 0, FALSE,IID_IPicture, (void**)&m_spIPicture);
　ASSERT(SUCCEEDED(hr) && m_spIPicture);
　return TRUE;
}

//////////////////
// Render to device context. Covert to HIMETRIC for IPicture.
BOOL CPicture::Render(CDC* pDC, CRect rc, LPCRECT prcMFBounds) const
{
　ASSERT(pDC);

　if (rc.IsRectNull()) {
　　CSize sz = GetImageSize(pDC);
　　rc.right = sz.cx;
　　rc.bottom = sz.cy;
　}
　long hmWidth,hmHeight; // HIMETRIC units
　GetHIMETRICSize(hmWidth, hmHeight);
　m_spIPicture->Render(*pDC, rc.left, rc.top, rc.Width(), rc.Height(),0, hmHeight, hmWidth, -hmHeight, prcMFBounds);
　return TRUE;
}

//////////////////
// Get image size in pixels. Converts from HIMETRIC to device coords.
CSize CPicture::GetImageSize(CDC* pDC) const
{
　if (!m_spIPicture)
　　return CSize(0,0);
　LONG hmWidth, hmHeight; // HIMETRIC units
　m_spIPicture->get_Width(&hmWidth);
　m_spIPicture->get_Height(&hmHeight);
　CSize sz(hmWidth,hmHeight);
　if (pDC==NULL) {
　　CWindowDC dc(NULL);
　　dc.HIMETRICtoDP(&sz); // convert to pixels
　} else {
　　pDC->HIMETRICtoDP(&sz);
　}
　return sz;
}

///////////////////////////////////// Picture view is a typical scroll view.
#include "Doc.h"
class CPictureView : public CScrollView {
　public:
　　virtual ~CPictureView();
　　CPictureDoc* GetDocument() { return (CPictureDoc*)m_pDocument; }
　protected:
　　BOOL m_rcImage; // rect to display image in
　　UINT m_iHowScale; // how to scale image
　　CPictureView();
　　void GetImageRect(CRect& rc);
　　void SetScrollSizes();
　　virtual void OnDraw(CDC* pDC); // overridden to draw this view
　　virtual void OnInitialUpdate(); // called first time after construct
　　// command/message handlers
　　afx_msg void OnViewScale(UINT nID);
　　afx_msg void OnUpdateViewScale(CCmdUI* pCmdUI);
　　afx_msg BOOL OnEraseBkgnd(CDC* pDC);
　　afx_msg void OnSize(UINT nType, int cx, int cy);
　　DECLARE_DYNCREATE(CPictureView)
　　DECLARE_MESSAGE_MAP()
};

////////////////////////////////////////////////////////////// CPictureView

#include "StdAfx.h"
#include "View.h"
#include "resource.h"
#ifdef _DEBUG
#define new DEBUG_NEW
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif
IMPLEMENT_DYNCREATE(CPictureView, CScrollView)

BEGIN_MESSAGE_MAP(CPictureView, CScrollView)
　ON_WM_ERASEBKGND()
　ON_WM_SIZE()
　ON_COMMAND_RANGE(ID_VIEW_TOFIT, ID_VIEW100, OnViewScale)
　ON_UPDATE_COMMAND_UI_RANGE(ID_VIEW_TOFIT, ID_VIEW100, OnUpdateViewScale)
END_MESSAGE_MAP()

CPictureView::CPictureView()
{
　m_iHowScale = ID_VIEW_TOFIT;
}

CPictureView::~CPictureView()
{}

void CPictureView::OnInitialUpdate()
{
　SetScrollSizes();
}

//////////////////// Set scroll sizes based on picture. Page size = client hieight/width;
// line size = 1/10 of this.
void CPictureView::SetScrollSizes()
{
　CRect rcClient;
　GetClientRect(&rcClient);
　CRect rcImage;
　GetImageRect(rcImage);
　CSize szTotal = rcImage.Size();
　CSize szPage = rcClient.Size();
　CSize szLine = szPage;
　szLine.cx /= 10;
　szLine.cy /= 10;
　CScrollView::SetScrollSizes(MM_TEXT, szTotal, szPage, szLine);
　Invalidate();
}

//////////////////// View was sized: readjust scroll sizes if I'm in "zoom to fit" mode
void CPictureView::OnSize(UINT nType, int cx, int cy)
{
　CScrollView::OnSize(nType, cx, cy);
　if (m_iHowScale==ID_VIEW_TOFIT) {
　　SetScrollSizes();
　}
}

//////////////////
// Erase the background. This is required in case the image is smaller than
// the client area, to paint the extra background. Use clipping to avoid flicker.
BOOL CPictureView::OnEraseBkgnd(CDC* pDC)
{
　CPictureDoc* pDoc = GetDocument();
　ASSERT_VALID(pDoc);
　// get client rectangle
　CRect rcClient;
　GetClientRect(&rcClient);
　CRect rc = rcClient;
　// get image rectangle
　CRect rcImage;
　GetImageRect(rcImage);
　rc = rcImage;
　CPoint pt = pDC->GetViewportOrg();
　CSize sz = GetTotalSize();
　// create clipping region
　CRgn clipRgn;
　clipRgn.CreateRectRgnIndirect(&rcClient);
　pDC->SelectClipRgn(&clipRgn);
　pDC->ExcludeClipRect(&rcImage);
　CBrush brush(RGB(0,0,0)); // black
　pDC->FillRect(&rcClient, &brush);
　pDC->SelectClipRgn(NULL);
　return TRUE;
}

//////////////////
// Draw the picture -- call CPicture to do it.
void CPictureView::OnDraw(CDC* pDC)
{
　CPictureDoc* pDoc = GetDocument();
　ASSERT_VALID(pDoc);
　CPicture* ppic = pDoc->GetPicture();
　ASSERT(ppic);
　if (*ppic) {
　　CRect rc;
　　GetImageRect(rc);
　　ppic->Render(pDC,rc);
　}
}

//////////////////
// Get image rectangle, scaled for current zoom factor.
void CPictureView::GetImageRect(CRect& rc)
{
　CPictureDoc* pDoc = GetDocument();
　ASSERT_VALID(pDoc);
　CPicture* ppic = pDoc->GetPicture();
　ASSERT(ppic);
　if (!ppic || !*ppic) {
　　rc.SetRect(0,0,0,0);
　} else if (m_iHowScale==ID_VIEW_TOFIT) {
　　GetClientRect(&rc);
　} else {
　　CSize sz = ppic->GetImageSize();
　　switch (m_iHowScale) {
　　　case ID_VIEW25:
　　　　sz.cx >>= 2;
　　　　sz.cy >>= 2;
　　　　break;
　　　case ID_VIEW33:
　　　　sz.cx /= 3;
　　　　sz.cy /= 3;
　　　　break;
　　　case ID_VIEW50:
　　　　sz.cx >>= 1;
　　　　sz.cy >>= 1;
　　　　break;
　　　case ID_VIEW75:
　　　　sz.cx = (sz.cx * 3)/4;
　　　　sz.cy = (sz.cy * 3)/4;
　　　　break;
　　}
　　rc.SetRect(0,0,sz.cx,sz.cy);
　}
}

//////////////////
// Handle zoom command.
void CPictureView::OnViewScale(UINT nID)
{
　if (m_iHowScale != nID) {
　　m_iHowScale = nID;
　　ScrollToPosition(CPoint(0,0));
　　OnInitialUpdate();
　}
}

//////////// Update zoom menu -- check the whichever zoom factor I'm at now.
void CPictureView::OnUpdateViewScale(CCmdUI* pCmdUI)
{
　pCmdUI->SetCheck(pCmdUI->m_nID == m_iHowScale);
}

　　四、小结

　　本实例通过Cpicutre类现了JEPG图像的显示，读者可以将该类直接用在多媒体应用程序的开发中。另外，MFC提供了一个现成的类--CPictureHolder，这个类的功能几乎与CPicture完全一样，读者朋友可以在afxctl.h文件中找到它的定义。

查看本文源

VIP专区

VIP用户

普通用户

邮件订阅

如果您非常迫切的想了解IT领域最新产品与技术信息，那么订阅至顶网技术邮件将是您的最佳途径之一。

重磅专题

往期文章

在MFC应用程序中显示JPG/GIF图像文件

业界热点: