c#获取图片正确格式的方法

var ext = Path.GetExtension("C:\\coderbusy.jpg");
Console.WriteLine(ext);

var img = Image.FromFile(@"D:\coderbusy.jpg");
Console.WriteLine(img.RawFormat.ToString());

public static class ImageHelper
{
	static ImageHelper()
	{
		lock (typeof(ImageHelper))
		{
			_mapping = GetImageFormatMapping();
		}
	}
	private static IDictionary<Guid, String> _mapping;
	private static IDictionary<Guid, String> GetImageFormatMapping()
	{
		var dic = new Dictionary<Guid, String>();
		var properties = typeof(ImageFormat).GetProperties(
			BindingFlags.Static | BindingFlags.Public
		);
		foreach (var property in properties)
		{
			var format = property.GetValue(null, null) as ImageFormat;
			if (format == null) continue;
			dic[format.Guid] = "." + property.Name.ToLower();
		}
		return dic;
	}

	public static String GetExtension(Image image)
	{
		var format = image.RawFormat;
		if (_mapping.ContainsKey(format.Guid))
		{
			return _mapping[format.Guid];
		}
		return String.Empty;
	}
}

var img = Image.FromFile(@"D:\coderbusy.jpg");
var ext = ImageHelper.GetExtension(img);
Console.WriteLine(ext);