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Distribution of this memo is unlimited.
Initial proposals were in the png-mng-misc mailing list, January 2017.
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It is proposed to add the following section to the document "Extensions to the PNG 1.2 Specification, Version 1.2.0"
101 88 73 102 (ASCII "e X I f")
When present, the eXIf chunk contains contains EXIF metadata that is compatible with specifications issued by CIPA, "Exchangeable image file format for digital still cameras" [CIPA DC-008-2016] or its successors. See https://www.media.mit.edu/pia/Research/deepview/exif.html
The eXIf chunk contains an EXIF profile in a raw format:
Data: length bytes where "length" is determined
by the chunk "length" field, containing a
raw EXIF profile.
At most one eXIF chunk shall occur in a PNG datastream. There are no ordering constraints upon the position of the eXIf beyond those imposed by the PNG specification, i.e., if present, the eXIf chunk may appear anywhere between the IHDR and IEND chunks except between IDAT chunks.
It is proposed to add the following section to the document "Extensions to the PNG 1.2 Specification, Version 1.2.0"
101 88 73 102 (ASCII "e X I f")
When present, the eXIf chunk contains contains EXIF metadata that is compatible with specifications issued by CIPA, "Exchangeable image file format for digital still cameras" [CIPA DC-008-2016] or its successors. See https://www.media.mit.edu/pia/Research/deepview/exif.html
The eXIf chunk contains an optional "mode" byte followed by an EXIF profile in a raw format or in a zlib-encoded compressed format:
Mode: 1 byte
0: the remaining length-1 bytes of data make up a
zlib-encoded EXIF profile written in accordance
with chapter 5, "Deflate/Inflate Compression"
of the PNG specification version 1.2 (which
is Clause 10.1, "Compression method 0" of the
ISO PNG specification).
69: (ASCII "E") the remaining length-1 bytes of
data, combined with the byte "E", make up a raw
uncompressed EXIF profile
Other values of Mode are reserved for other
compression methods which might be defined
in a future version of this specification.
Data: the remaining length-1 bytes where "length" is
determined by the chunk "length" field
At most one eXIF chunk shall occur in a PNG datastream. There are no ordering constraints upon the position of the eXIf beyond those imposed by the PNG specification, i.e., if present, the eXIf chunk may appear anywhere between the IHDR and IEND chunks except between IDAT chunks.