笔记:使用 JavaScript 读取 JPEG 文件 EXIF 中的 Orientation - 4. Brief on Exif's IFD(Image File Directory):
>> Exif's IFD(Image File Directory):
+------+---------------------------+
| Exif | ··· |
+ +---------------------------+
| | IFD0 | XXXX |
+ + +--------------------+
| | | entry 1 |
+ + +--------------------+
| | | entry n |
+ + +--------------------+
| | | offset to next IFD |
+ +------+--------------------+
| | ··· |
+------+---------------------------+