Try this.

#define GDIPLUS_ROTATEFLIPTYPE_RotateNoneFlipNone 0
#define GDIPLUS_ROTATEFLIPTYPE_Rotate90FlipNone   1
#define GDIPLUS_ROTATEFLIPTYPE_Rotate180FlipNone  2
#define GDIPLUS_ROTATEFLIPTYPE_Rotate270FlipNone  3

#define GDIPLUS_ROTATEFLIPTYPE_RotateNoneFlipX    4
#define GDIPLUS_ROTATEFLIPTYPE_Rotate90FlipX      5
#define GDIPLUS_ROTATEFLIPTYPE_Rotate180FlipX     6
#define GDIPLUS_ROTATEFLIPTYPE_Rotate270FlipX     7

oImage= newobject(GpBitmap','ffc/_gdiplus.vcx')
oImage.CreateFromFile(GETpic())
oImage.RotateFlip(GDIPLUS_ROTATEFLIPTYPE_Rotate180FlipNone )
oImg=oImage.GetThumbnailImage(32,33)
oImg.SaveToFile('c:\ImgRot.jpg',"image/jpeg",'quality=100')

>I have a large number of tiff images I need to rotate 180 degrees.
>
>What is the most effective way to do this?