VC 实现BMP转换到JPG、JPG转换到BMP

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 );

************************************************************/

void SaveFile(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岽笮?   ys = 图象y轴大小,   quality = jpeg图象质量
void SaveCurScreenJpg(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;

}