vs2008中GDI+的使用方法

将bmp转成jpg格式:

方法一(优点:能控制压缩比):
int GetEncoderClsid(const WCHAR* format, CLSID* pClsid) 
{ 
    UINT num = 0;                     // number of image encoders 
    UINT size = 0;                   // size of the image encoder array in bytes 
    ImageCodecInfo* pImageCodecInfo = NULL; 
    GetImageEncodersSize(&num, &size); 
    if(size == 0) 
        return -1;     //   Failure 
  
    pImageCodecInfo = (ImageCodecInfo*)(malloc(size)); 
    if(pImageCodecInfo == NULL) 
        return -1;     //   Failure 
  
    GetImageEncoders(num, size, pImageCodecInfo); 
    for(UINT j = 0; j < num; ++j) 
    { 
        if( wcscmp(pImageCodecInfo[j].MimeType, format) == 0 ) 
        { 
            *pClsid = pImageCodecInfo[j].Clsid; 
            free(pImageCodecInfo); 
            return j;     //   Success 
        }         
    } 
    free(pImageCodecInfo); 
    return -1;     //   Failure 
}
 
/****************BMP转JPG*********用法示例**************************
Bitmap newbitmap(L"d:\\d.bmp");//加载BMP
const unsigned short *pFileName=L"d:\\new.jpg";//保存路径
SaveFile(&newbitmap,pFileName );
************************************************************/
voidSaveFile(Bitmap* pImage, const wchar_t* pFileName)//
{
    EncoderParameters encoderParameters;
    CLSID jpgClsid;
GetEncoderClsid(L"image/jpeg", &jpgClsid);
    encoderParameters.Count = 1;
    encoderParameters.Parameter[0].Guid = EncoderQuality;
    encoderParameters.Parameter[0].Type = EncoderParameterValueTypeLong;
    encoderParameters.Parameter[0].NumberOfValues = 1;
    // Save the image as a JPEG with quality level 100.
    ULONG             quality;
    quality = 100;
    encoderParameters.Parameter[0].Value = &quality;
    Status status = pImage->Save(pFileName, &jpgClsid, &encoderParameters);
    if (status != Ok)
    {
        wprintf(L"%d Attempt to save %s failed.\n", status, pFileName);
    }
}

// 将当前屏幕保存成为jpg图片     
// 参数   xs = 图象x轴大小,   ys = 图象y轴大小,   quality = jpeg图象质量     
voidSaveCurScreenJpg(LPCWSTR   pszFileName,   int   xs,   int   ys,   int   quality) 
{ 
    HWND hwnd = ::GetDesktopWindow(); 
    HDC hdc = GetWindowDC(NULL); 
    int x = GetDeviceCaps(hdc, HORZRES); 
    int y = GetDeviceCaps(hdc, VERTRES); 
    HBITMAP hbmp = ::CreateCompatibleBitmap(hdc, x, y), hold; 
    HDC hmemdc = ::CreateCompatibleDC(hdc); 
    hold = (HBITMAP)::SelectObject(hmemdc,   hbmp); 
    BitBlt(hmemdc, 0, 0, x, y, hdc, 0, 0, SRCCOPY); 
    SelectObject(hmemdc, hold); 
  
    Bitmap bit(xs, ys), bit2(hbmp, NULL); 
    Graphics g(&bit); 
    g.ScaleTransform((float)xs/x,   (float)ys/y); 
    g.DrawImage(&bit2,   0,   0); 
  
    CLSID                           encoderClsid; 
    EncoderParameters   encoderParameters; 
  
    encoderParameters.Count   =   1; 
    encoderParameters.Parameter[0].Guid   =   EncoderQuality; 
    encoderParameters.Parameter[0].Type   =   EncoderParameterValueTypeLong; 
    encoderParameters.Parameter[0].NumberOfValues   =   1; 
    encoderParameters.Parameter[0].Value   =   &quality; 
  
    GetEncoderClsid(L"image/jpeg",   &encoderClsid); 
    bit.Save(pszFileName,   &encoderClsid,   &encoderParameters); 
 
    ::DeleteObject(hbmp); 
    ::DeleteObject(hmemdc); 
    return; 
} 

HBITMAP  ReturnHBITMAP(CString   FileName)//FileName可能是bmp、dib、png、gif、jpeg/jpg、tiff、emf等文件的文件名
{
          Bitmap   tempBmp(FileName.AllocSysString())   ;
        Color       backColor;     
        HBITMAP       HBitmap; 
        tempBmp.GetHBITMAP(backColor,&HBitmap);
        return   HBitmap;
}

方法二(优点:简单;缺点:不能控制压缩比):
bool CCaptureWindow::SaevBitmapToJpg(HBITMAP hBitmap, LPCTSTR lpFileName)

{

CImage img;

img.Attach(hBitmap);

HRESULT hResult = img.Save(lpFileName);

DeleteObject(hBitmap);

return TRUE;

}