用GDI+对图象旋转和缩小后,发现图象有失真的现象!

Question

最近有个项目,把一JPEG图片旋转 后要缩小到一寸的大小.用GDI+进行上述操作后发现图片有失真的现象, 可客户要拿图片冲洗照片.所以解决这个问题一直很头疼. 
    听说有算法可避免上述现象,   最好还是用GDI+ ,能给出VC++的代码最好.  
    谢谢了

Answer 1

#pragma once 
#ifndef __ENHANCED_SHRINK_HPP__
#define __ENHANCED_SHRINK_HPP__
//shrink using GDI+
struct GdiplusManager
{
GdiplusManager();
~GdiplusManager();
bool gdiplus_ok;
ULONG gdiplusToken; 
};int GDIPlus_StretchDIBits(
  HDC hdc,                      // handle to DC
  int XDest,                    // x-coord of destination upper-left corner
  int YDest,                    // y-coord of destination upper-left corner
  int nDestWidth,               // width of destination rectangle
  int nDestHeight,              // height of destination rectangle
  int XSrc,                     // x-coord of source upper-left corner
  int YSrc,                     // y-coord of source upper-left corner
  int nSrcWidth,                // width of source rectangle
  int nSrcHeight,               // height of source rectangle
  CONST VOID *lpBits,           // bitmap bits
  CONST BITMAPINFO *lpBitsInfo, // bitmap data
  UINT iUsage,                  // usage options
  DWORD dwRop                   // raster operation code
);#endif

Answer 2

#include "StdAfx.h"
//need to have D:\Apps\Microsoft SDK\Include preceeds VC standard headers 
#include "enhanced_shrink.h"
#include <windows.h>
#include <Objbase.h>
#include <Gdiplus.h>
#include <GdiPlusEnums.h>
#pragma comment(lib,"gdiplus")
#pragma comment(lib, "delayimp.lib")
#pragma comment(linker, "/VERBOSE:LIB")
#include <memory>
#include <comutil.h>
#pragma comment(lib,"comsupp.lib")
using namespace Gdiplus;
GdiplusManager::GdiplusManager()
{
Gdiplus::GdiplusStartupInput gdiplusStartupInput; 
Gdiplus::Status gdiplus_status;
gdiplus_status = Gdiplus::GdiplusStartup(&gdiplusToken, &gdiplusStartupInput, NULL); 
if(Gdiplus::Ok == gdiplus_status)
gdiplus_ok = true;
}
GdiplusManager::~GdiplusManager()
{
if(gdiplus_ok)
Gdiplus::GdiplusShutdown(gdiplusToken);
}GdiplusManager global_gdi_object;//must be global objectint GDIPlus_StretchDIBits(
  HDC hdc,                      // handle to DC
  int XDest,                    // x-coord of destination upper-left corner
  int YDest,                    // y-coord of destination upper-left corner
  int nDestWidth,               // width of destination rectangle
  int nDestHeight,              // height of destination rectangle
  int XSrc,                     // x-coord of source upper-left corner
  int YSrc,                     // y-coord of source upper-left corner
  int nSrcWidth,                // width of source rectangle
  int nSrcHeight,               // height of source rectangle
  CONST VOID *lpBits,           // bitmap bits
  CONST BITMAPINFO *lpBitsInfo, // bitmap data
  UINT iUsage,                  // usage options
  DWORD dwRop                   // raster operation code
)
{
if(false == global_gdi_object.gdiplus_ok 
|| nDestHeight >= nSrcHeight 
|| nDestWidth >= nSrcWidth)
{
int nret = StretchDIBits(hdc,XDest,YDest,nDestWidth,nDestHeight,
XSrc,YSrc,nSrcWidth,
nSrcHeight,lpBits,lpBitsInfo,iUsage,dwRop);
return nret;
}
try
{
typedef std::auto_ptr<Bitmap> PtrBitmap;
PtrBitmap imgPhoto(Bitmap::FromBITMAPINFO(lpBitsInfo,(void*)lpBits)) ;
Bitmap bmptmp(nDestWidth, nDestHeight, PixelFormat24bppRGB);
Bitmap* bmPhoto = &bmptmp;
bmPhoto->SetResolution(imgPhoto->GetHorizontalResolution(), 
imgPhoto->GetVerticalResolution());
std::auto_ptr<Graphics> grPhoto (Graphics::FromImage(bmPhoto));
grPhoto->Clear(Color.White);
grPhoto->SetInterpolationMode( InterpolationModeHighQualityBilinear);
Point destPoints[3];
destPoints[0].X = XDest;  //left top
destPoints[0].Y = YDest;
destPoints[1].X = XDest + nDestWidth; //right top
destPoints[1].Y = YDest;
destPoints[2].X = XDest; //left bottom
destPoints[2].Y = YDest + nDestHeight;
grPhoto->DrawImage(imgPhoto.get(),(const Point*)destPoints,3,XSrc,
YSrc,nSrcWidth,nSrcHeight,UnitPixel,
NULL,NULL,NULL);
HBITMAP hbmp = NULL;
Color background;
bmPhoto->GetHBITMAP(background,&hbmp);
BITMAP bm;
GetObject(hbmp,sizeof(bm),&bm);
HDC dcmem;
dcmem = CreateCompatibleDC(hdc);
::SelectObject(dcmem,hbmp);
::BitBlt(hdc,XDest,YDest,nDestWidth,nDestHeight,dcmem,XSrc,YSrc,SRCCOPY);
}
catch(...)
{
int nret = StretchDIBits(hdc,XDest,YDest,nDestWidth,nDestHeight,
XSrc,YSrc,nSrcWidth,
nSrcHeight,lpBits,lpBitsInfo,iUsage,dwRop);
return nret;
}
return 0;
}

Answer 3

to :masterz(www.fruitfruit.com) 
grPhoto->SetInterpolationMode( InterpolationModeHighQualityBilinear);用GDI+的这个方法不行么? 怎么如此复杂!!!

Answer 4

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