//获得图片
Image bg = Image.FromFile("文件地址");
//获得Graphics
Graphics g = CreateGraphics();
//以图片中心为原点平移
g.TranslateTransform(bg.Width/2 ,bgg.Height/2);
//旋转度数
int i = 60;
g.RotateTransform(i);
g.TranslateTransform(-bg.Width/2,-bgg.Height/2);
//重置
g.ResetTransform();