JEITA CP-3451
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4.6 Tags
4.6.1 Features of Attribute Information
RGB data conforms to Baseline TIFF Rev. 6.0 RGB Full Color Images, and YCbCr data to TIFF Rev. 6.0
Extensions YCbCr Images. Accordingly, the parts that follow the TIFF structure shall be recorded in conformance to
the TIFF standard. In addition to the attribute information indicated as mandatory in the TIFF standard, this Exif
standard adds the TIFF optional tags that can be used in a DSC or other system, Exif-specific tags for recording
DSC-specific attribute information, and GPS tags for recording position information. There are also Exif-original
specifications not found in the TIFF standard for compressed recording of thumbnails.
Recording of compressed data differs from uncompressed data in the following respects:
· When the primary image data is recorded in compressed form, there is no tag indicating the primary image
itself or its address (pointer),
· When thumbnail data is recorded in compressed form, address and size are designated using Exif-specific
tags,
· Tags that duplicate information given in the JPEG Baseline are not recorded (for either primary images or
thumbnails).
· Information relating to compression can be recorded using the tags for this purpose.
4.6.2 IFD Structure
The IFD used in this standard consists of a 2-byte count (number of fields), 12-byte field Interoperability arrays, and
4-byte offset to the next IFD, in conformance with TIFF Rev. 6.0.
Each of the 12-byte field Interoperability consists of the following four elements respectively.
Bytes 0-1
Tag
Bytes 2-3
Type
Bytes 4-7
Count
Bytes 8-11
Value Offset
Each element is explained briefly below. For details see TIFF Rev. 6.0.