/// <summary>
/// C# Image图片格式转换(gif/jpg/png/bmp)
/// </summary>
/// <param name="img"></param>
/// <param name="filePath"></param>
/// <returns></returns>
public bool SaveJpeg(Image img, string filePath)
{
    try
    {
        using (var bmp = new Bitmap(img.Width, img.Height))
        {
            bmp.SetResolution(img.HorizontalResolution, img.VerticalResolution);

            using (var g = Graphics.FromImage(bmp))
            {
                g.Clear(Color.White);
                g.DrawImageUnscaled(img, 0, 0);
            }

            //存储各种格式
            //bmp.Save(filePath, System.Drawing.Imaging.ImageFormat.Gif);
            //bmp.Save(filePath, System.Drawing.Imaging.ImageFormat.Png);
            bmp.Save(filePath, System.Drawing.Imaging.ImageFormat.Jpeg);
        }

        return true;
    }
    catch
    {
        return false;
    }
}