GDI+调整图像文件尺寸大小

stdafx.h

#include "gdiplus.h" 

using namespace Gdiplus; 

#pragma comment( lib, "gdiplus.lib" )

class CImageResizeApp : public CWinApp

{

public:
CImageResizeApp();

GdiplusStartupInput    m_Gdistart; 
ULONG_PTR    m_GdiplusToken; 

BOOL CImageResizeApp::InitInstance()

{

GdiplusStartup(&m_GdiplusToken,&m_Gdistart,NULL);

}

int CImageResizeApp::ExitInstance()

{
// TODO: 在此添加专用代码和/或调用基类
GdiplusShutdown(m_GdiplusToken);

return CWinApp::ExitInstance();

}

void ResizePicture(LPCWSTR   lpSrcFile,LPCWSTR   lpDstFile,int   wRatio,int   hRatio)        

{ 
Image     srcImg(lpSrcFile); 
int   srcWidth=srcImg.GetWidth(); 
int   srcHeight=srcImg.GetHeight(); 
//计算调整后的Width和Height 
int   dstWidth=srcWidth*wRatio; 
int   dstHeight=srcHeight*hRatio; 
//   Construct   a   Graphics   object   based   on   the   image. 
Graphics   imgGraphics(&srcImg); 

Bitmap   bitmap(dstWidth,dstHeight,&imgGraphics); 
Graphics   bmpGraphics(&bitmap); 
bmpGraphics.DrawImage(&srcImg,0,0,dstWidth,dstHeight); 
//   Save   the   altered   image. 
const  wchar_t*   lpExt=wcsrchr(lpSrcFile, '.');
if(!lpExt)
return; 
lpExt++; 
LPWSTR   lpEncoder; 
switch(*lpExt) 
{ 
case    'J ': 
case   'j ': 
lpEncoder=L"image/jpeg "; 
break; 
case   'P ': 
case    'p ': 
lpEncoder=L"image/png "; 
break; 
case   'B ': 
case    'b ': 
lpEncoder=L"image/bmp "; 
break; 
case    'G ': 
case   'g ': 
lpEncoder=L"image/gif "; 
break; 
case    't ': 
case    'T ': 
lpEncoder=L"image/tiff "; 
break; 
default: 
lpEncoder=L"image/jpeg "; 
} 

CLSID   imgClsid; 
GetEncoderClsid(lpEncoder,   &imgClsid); 
bitmap.Save(lpDstFile,&imgClsid,NULL); 

}

int GetEncoderClsid(const WCHAR* format, CLSID* pClsid)

{
UINT num= 0;
UINT size= 0;

ImageCodecInfo* pImageCodecInfo= NULL;

GetImageEncodersSize(&num, &size);
if(size== 0)
{
return -1;
}
pImageCodecInfo= (ImageCodecInfo*)(malloc(size));
if(pImageCodecInfo== NULL)
{
return -1;
}

GetImageEncoders(num, size, pImageCodecInfo);

for(UINT j=0; j< num; ++j)
{
//if(wcsstr(pImageCodecInfo[j].MimeType, format))
{
*pClsid= pImageCodecInfo[1].Clsid;
free(pImageCodecInfo);
return j;
}
}

free(pImageCodecInfo);
return -1;
}

call       ResizePicture(L"QQ2.png",L"test.png",2,2);