iOS判断UIImage图片类型

+ (NSString *)typeForImageData:(NSData *)data{    

     uint8_t c;

     [data getBytes:&c length:1];

    switch (c)

    {

    case 0xFF:

    return @"image/jpeg";

    case 0x89:

    return @"image/png";

    case 0x47:

    return @"image/gif";

    case 0x49:

    case 0x4D:

    return @"image/tiff";

    }

    return nil;

}