[C#]旋转图片

#region 图片旋转函数

/// <summary>--以顺时针为方向对图像进行旋转--
/// Guo Jin
/// </summary>
/// <param name="b">位图流</param>
/// <param name="angle">旋转角度[0,360](前台给的)</param>
/// <returns></returns>
private Image RotateImg(Image b, int angle)
{
    angle = angle % 360;
    //弧度转换
    double radian = angle * Math.PI / 180.0;
    double cos = Math.Cos(radian);
    double sin = Math.Sin(radian);
    //原图的宽和高
    int w = b.Width;
    int h = b.Height;
    int W = (int)(Math.Max(Math.Abs(w * cos - h * sin), Math.Abs(w * cos + h * sin)));
    int H = (int)(Math.Max(Math.Abs(w * sin - h * cos), Math.Abs(w * sin + h * cos)));
    //目标位图
    Bitmap dsImage = new Bitmap(W, H);
    System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(dsImage);
    g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.Bilinear;
    g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
    //计算偏移量
    Point Offset = new Point((W - w) / 2, (H - h) / 2);
    //构造图像显示区域：让图像的中心与窗口的中心点一致
    Rectangle rect = new Rectangle(Offset.X, Offset.Y, w, h);
    Point center = new Point(rect.X + rect.Width / 2, rect.Y + rect.Height / 2);
    g.TranslateTransform(center.X, center.Y);
    g.RotateTransform(360 - angle);
    //恢复图像在水平和垂直方向的平移
    g.TranslateTransform(-center.X, -center.Y);
    g.DrawImage(b, rect);
    //重至绘图的所有变换
    g.ResetTransform();
    g.Save();
    g.Dispose();
    //保存旋转后的图片
    b.Dispose();
    //try
    //{
    //    if (this.tabControl1.SelectedIndex == 0)
    //    {
    //        //dsImage.Save(GlobalInfo.AppPath + file1, System.Drawing.Imaging.ImageFormat.Jpeg);
    //    }
    //    else if (this.tabControl1.SelectedIndex == 1)
    //    {
    //        //dsImage.Save(GlobalInfo.AppPath + file2, System.Drawing.Imaging.ImageFormat.Jpeg);
    //    }
    //}
    //catch (Exception ex)
    //{ }
    return dsImage;
}

private Image RotateImg(string filename, int angle)
{
    return RotateImg(GetSourceImg(filename), angle);
}

private Image GetSourceImg(string filename)
{
    Image img;
    img = Bitmap.FromFile(filename);
    return img;
}

#endregion 图片旋转函数

//使用方法
Image g = RotateImg(GlobalInfo.AppPath + file1, -90);