EXIFGetInfo EXIFGetVersion
A tag for Exif users to write keywords or comments on the image besides those in < ImageDescription> , and without the character code limitations of the < ImageDescription> tag. The character code used in the < UserComment> tag is identified based on an ID code in a fixed 8-byte area at the start of the tag data area. The unused portion of the area is padded with NULL (00.h). ID codes are assigned by means of registration. The designation method and references for each character code are given in Table 6. The value of CountN is determinated based on the 8 bytes in the character code area and the number of bytes in the user comment part. Since the TYPE is not ASCII, NULL termination is not necessary (see Fig. 9). The ID code for the < UserComment> area may be a Defined code such as JIS or ASCII, or may be Undefined. The Undefined name is UndefinedText, and the ID code is filled with 8 bytes of all NULL (00.H). An Exif reader that reads the < UserComment> tag must have a function for determining the ID code. This function is not required in Exif readers that do not use the < UserComment> tag (see Table 7). When a < UserComment> area is set aside, it is recommended that the ID code be ASCII and that the following user comment part be filled with blank characters [20.H]. Define restart interval Information specific to compressed data. The channels of each component are arranged in order from the 1st component to the 4th. For uncompressed data the data arrangement is given in the < PhotometricInterpretation> tag. However, since < PhotometricInterpretation> can only express the order of Y, Cb and Cr, this tag is provided for cases when compressed data uses components other than Y, Cb, and Cr and to enable support of other sequences. Information specific to compressed data. When a compressed file is recorded, the valid height of the meaningful image must be recorded in this tag, whether or not there is padding data or a restart marker. This tag should not exist in an uncompressed file. For details see section 2.8.1 and Appendix F. Since data padding is unnecessary in the vertical direction, the number of lines recorded in this valid image height tag will in fact be the same as that recorded in the SOF. Information specific to compressed data. When a compressed file is recorded, the valid width of the meaningful image must be recorded in this tag, whether or not there is padding data or a restart marker. This tag should not exist in an uncompressed file. For details see section 2.8.1 and Appendix F. Restart 1 Restart 2 Restart 3 Restart 4 Restart 5 Restart 6 Restart 7 Start of image Start of scan The offset to the start byte (SOI) of JPEG compressed thumbnail data. This is not used for primary image JPEG data.