VC加载jpeg, png图片的方法

在VC中我们可以直接利用LoadIcon, LoadBitmap或LoadImage来加载bmp和ico图片, 但是加载jpg和png等格式就没有这么方便了. 其实我们可以通过两个系统提供的两个com接口IPicture和IStream类实现类似于VB的Picture控件, 具体的用法请查看msdn或google下, 下面代码是我以前在网上找的一个例子, 主要用到了几个API函数: AfxGetResourceHandle, FindResource, SizeofResource, LoadResource, CreateStreamOnHGlobal, 如果需要保存为新的图片就需要用到IPicture接口了.

m_pImage = new CImage();
ImageFromIDResource(*m_pImage, IDB_PNG_IDISK, _T("PNG"));
HBITMAP hBitmap = m_pImage->Detach();
m_statBitmap.SetBitmap(hBitmap);
void  ImageFromIDResource(CImage& image, UINT nID, LPCTSTR lpType)
{
HINSTANCE hInst = AfxGetResourceHandle();
HRSRC hRsrc = ::FindResource (hInst,MAKEINTRESOURCE(nID),lpType);
if(hRsrc == NULL)
return;
DWORD dwLen = SizeofResource(hInst, hRsrc);
BYTE* lpRsrc = (BYTE*)LoadResource(hInst, hRsrc);
if (!lpRsrc)
return;;
HGLOBAL m_hMem = GlobalAlloc(GMEM_FIXED, dwLen);
BYTE* pmem = (BYTE*)GlobalLock(m_hMem);
memcpy(pmem,lpRsrc,dwLen);
IStream* pstm;
CreateStreamOnHGlobal(m_hMem,FALSE,&pstm);
image.Load(pstm);
GlobalUnlock(m_hMem);
pstm->Release();
FreeResource(lpRsrc);
}

另外, 网上还有一个用IPicture写的Picture类, 源码如下:

////////////////////////////////////////////////////////////////
// MSDN Magazine -- October 2001
// If this code works, it was written by Paul DiLascia.
// If not, I don't know who wrote it.
// Compiles with Visual C++ 6.0 for Windows 98 and probably Windows 2000 too.
// Set tabsize = 3 in your editor.
//
#pragma once
#include <atlbase.h>
//////////////////
// Picture object--encapsulates IPicture
//
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
};

#include "StdAfx.h"
#include "Picture.h"
#ifdef _DEBUG
#define new DEBUG_NEW
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif
////////////////////////////////////////////////////////////////
// CPicture implementation
//
CPicture::CPicture()
{
}
CPicture::~CPicture()
{
}
//////////////////
// Load from resource. Looks for "IMAGE" type.
//
BOOL CPicture::Load(UINT nIDRes)
{
// 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);
return bRet;
}
//////////////////
// Load from path name.
//
BOOL CPicture::Load(LPCTSTR pszPathName)
{
CFile file;
if (!file.Open(pszPathName, CFile::modeRead|CFile::shareDenyWrite))
return FALSE;
BOOL bRet = Load(file);
file.Close();
return bRet;
}
//////////////////
// Load from CFile
//
BOOL CPicture::Load(CFile& file)
{
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;
}