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fix: IPTC fields have length limits (#4568)
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It escaped our notice before that the IPTC spec dictates length limits
for many fields. Getting this wrong can confuse some software, including
Photoshop, apparently.

This patch enforces length limits wherever we could figure them out from
the IPTC spec -- it will simply truncate those strings that are too long
before writing them to a binary IPTC tag.

For this reason, we also are ending the practice of automatically
translating several IPTC fields to and from what we figured were the
equivalent generic metadata names. This was perhaps a dubious practice
to begin with, but now the enforcement of length limits for IPTC (but
not the generic metadata) makes it even more frought. There is probably
nobody depending on this behavior (and maybe few OIIO users depending on
IPTC support at all?), so now anybody purposely using IPTC metadata is
fully responsible for setting it and dealing with any issues of whether
it's "out of sync" with any other metadata that OIIO stores in or reads
from a file.

Fixes #4342

---------

Signed-off-by: Larry Gritz <[email protected]>
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lgritz authored Dec 28, 2024
1 parent 6b11c95 commit bff3377
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49 changes: 32 additions & 17 deletions src/doc/stdmetadata.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -916,23 +916,8 @@ conventions for storing image metadata, and this standard is growing in
popularity and is commonly used in photo-browsing programs to record
captions and keywords.

The following IPTC metadata items correspond exactly to metadata in the
OpenImageIO conventions, so it is recommended that you use the standards and
that plugins supporting IPTC metadata respond likewise:

=============== =========================================================================================================
IPTC tag OpenImageIO metadata convention
=============== =========================================================================================================
Caption `"ImageDescription"`
Keyword IPTC keywords should be concatenated, separated by semicolons (`;`), and stored as the `Keywords` attribute.
ExposureTime `ExposureTime`
CopyrightNotice `Copyright`
Creator `Artist`
=============== =========================================================================================================


The remainder of IPTC metadata fields should use the following names,
prefixed with `IPTC:` to avoid conflicts with other plugins or standards.
IPTC metadata fields should use the following names, prefixed with `IPTC:` to
avoid conflicts with other plugins or standards.

.. option:: "IPTC:ObjecTypeReference" : string

Expand All @@ -958,6 +943,10 @@ prefixed with `IPTC:` to avoid conflicts with other plugins or standards.

Category.

.. option:: "IPTC:Keywords" : string

Semicolon-separated keywords describing the contents of the image.

.. option:: "IPTC:ContentLocationCode" : string

Code for content location.
Expand All @@ -976,6 +965,10 @@ prefixed with `IPTC:` to avoid conflicts with other plugins or standards.

Expiration date and time.

.. option:: "IPTC:ExposureTime" : string

The exposure time (in seconds) of the captured image.

.. option:: "IPTC:Instructions" : string

Special instructions for handling the image.
Expand All @@ -1000,6 +993,10 @@ prefixed with `IPTC:` to avoid conflicts with other plugins or standards.

The version number of the creation software.

.. option:: "IPTC:Creator" : string

The artist, creator, or owner of the image.

.. option:: "IPTC:AuthorsPosition" : string

The job title or position of the creator of the image.
Expand All @@ -1025,11 +1022,19 @@ prefixed with `IPTC:` to avoid conflicts with other plugins or standards.

The source of the image.

.. option:: "IPTC:CopyrightNotice" : string

Any copyright notice for the image.

.. option:: "IPTC:Contact" : string

The contact information for the image (possibly including name, address,
email, etc.).

.. option:: "IPTC:Caption" : string

A caption for the image.

.. option:: "IPTC:CaptionWriter" : string

The name of the person who wrote the caption or description of the
Expand Down Expand Up @@ -1058,6 +1063,16 @@ prefixed with `IPTC:` to avoid conflicts with other plugins or standards.
The history of the image or document.


References for more information on IPTC metadata:

* https://www.iptc.org/std/photometadata/specification/IPTC-PhotoMetadata
* https://www.iptc.org/std/photometadata/specification/IPTC-PhotoMetadata#iptc-core-schema-1-5-specifications
This is the one where you can find the length limits
* ExifTool's documentation about IPTC tags (caveat: not a definitive
reference, could be outdated or incorrect):
https://exiftool.org/TagNames/IPTC.html


SMPTE metadata
==============

Expand Down
134 changes: 79 additions & 55 deletions src/libOpenImageIO/iptc.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -21,68 +21,78 @@ struct IIMtag {
const char* name; // Attribute name we use
const char* anothername; // Optional second name
bool repeatable; // May repeat
unsigned int maxlen; // Maximum length (if nonzero)
};

static IIMtag iimtag[] = {
{ 3, "IPTC:ObjectTypeReference", NULL, false },
{ 4, "IPTC:ObjectAttributeReference", NULL, true },
{ 5, "IPTC:ObjectName", NULL, false },
{ 7, "IPTC:EditStatus", NULL, false },
{ 10, "IPTC:Urgency", NULL, false }, // deprecated by IPTC
{ 12, "IPTC:SubjectReference", NULL, true },
{ 15, "IPTC:Category", NULL, false },
{ 20, "IPTC:SupplementalCategories", NULL, true }, // deprecated by IPTC
{ 22, "IPTC:FixtureIdentifier", NULL, false },
{ 25, "Keywords", NULL, true },
{ 26, "IPTC:ContentLocationCode", NULL, true },
{ 27, "IPTC:ContentLocationName", NULL, true },
{ 30, "IPTC:ReleaseDate", NULL, false },
{ 35, "IPTC:ReleaseTime", NULL, false },
{ 37, "IPTC:ExpirationDate", NULL, false },
{ 38, "IPTC:ExpirationTime", NULL, false },
{ 40, "IPTC:Instructions", NULL, false },
{ 45, "IPTC:ReferenceService", NULL, true },
{ 47, "IPTC:ReferenceDate", NULL, false },
{ 50, "IPTC:ReferenceNumber", NULL, true },
{ 55, "IPTC:DateCreated", NULL, false },
{ 60, "IPTC:TimeCreated", NULL, false },
{ 62, "IPTC:DigitalCreationDate", NULL, false },
{ 63, "IPTC:DigitalCreationTime", NULL, false },
{ 65, "IPTC:OriginatingProgram", "Software", false },
{ 70, "IPTC:ProgramVersion", NULL, false },
{ 80, "IPTC:Creator", "Artist", true }, // sometimes called "byline"
{ 85, "IPTC:AuthorsPosition", NULL, true }, // sometimes "byline title"
{ 90, "IPTC:City", NULL, false },
{ 92, "IPTC:Sublocation", NULL, false },
{ 95, "IPTC:State", NULL, false }, // sometimes "Province/State"
{ 100, "IPTC:CountryCode", NULL, false },
{ 101, "IPTC:Country", NULL, false },
{ 103, "IPTC:TransmissionReference", NULL, false },
{ 105, "IPTC:Headline", NULL, false },
{ 110, "IPTC:Provider", NULL, false }, // aka Credit
{ 115, "IPTC:Source", NULL, false },
{ 116, "IPTC:CopyrightNotice", "Copyright", false },
{ 118, "IPTC:Contact", NULL, false },
{ 120, "IPTC:Caption", "ImageDescription", false },
{ 121, "IPTC:LocalCaption", NULL, false },
{ 122, "IPTC:CaptionWriter", NULL, false }, // aka Writer/Editor
{ 3, "IPTC:ObjectTypeReference", NULL, false, 67 },
{ 4, "IPTC:ObjectAttributeReference", NULL, true, 68 },
{ 5, "IPTC:ObjectName", NULL, false, 64 },
{ 7, "IPTC:EditStatus", NULL, false, 64 },
{ 10, "IPTC:Urgency", NULL, false, 1 }, // deprecated by IPTC
{ 12, "IPTC:SubjectReference", NULL, true, 236 },
{ 15, "IPTC:Category", NULL, false, 3 },
{ 20, "IPTC:SupplementalCategories", NULL, true, 32 }, // deprecated by IPTC
{ 22, "IPTC:FixtureIdentifier", NULL, false, 32 },
{ 25, "IPTC:Keywords", NULL, true, 64 },
{ 26, "IPTC:ContentLocationCode", NULL, true, 3 },
{ 27, "IPTC:ContentLocationName", NULL, true, 64 },
{ 30, "IPTC:ReleaseDate", NULL, false, 8 },
{ 35, "IPTC:ReleaseTime", NULL, false, 11 },
{ 37, "IPTC:ExpirationDate", NULL, false, 8 },
{ 38, "IPTC:ExpirationTime", NULL, false, 11 },
{ 40, "IPTC:Instructions", NULL, false, 256 },
{ 45, "IPTC:ReferenceService", NULL, true, 10 },
{ 47, "IPTC:ReferenceDate", NULL, false, 8 },
{ 50, "IPTC:ReferenceNumber", NULL, true, 8 },
{ 55, "IPTC:DateCreated", NULL, false, 8 },
{ 60, "IPTC:TimeCreated", NULL, false, 11 },
{ 62, "IPTC:DigitalCreationDate", NULL, false, 8 },
{ 63, "IPTC:DigitalCreationTime", NULL, false, 11 },
{ 65, "IPTC:OriginatingProgram", "Software", false, 32 },
{ 70, "IPTC:ProgramVersion", NULL, false, 10 },
{ 80, "IPTC:Creator", "Artist", true, 32 }, // sometimes called "byline"
{ 85, "IPTC:AuthorsPosition", NULL, true, 32 }, // sometimes "byline title"
{ 90, "IPTC:City", NULL, false, 32 },
{ 92, "IPTC:Sublocation", NULL, false, 32 },
{ 95, "IPTC:State", NULL, false, 32 }, // sometimes "Province/State"
{ 100, "IPTC:CountryCode", NULL, false, 3 },
{ 101, "IPTC:Country", NULL, false, 64 },
{ 103, "IPTC:TransmissionReference", NULL, false, 32 },
{ 105, "IPTC:Headline", NULL, false, 256 },
{ 110, "IPTC:Provider", NULL, false, 32 }, // aka Credit
{ 115, "IPTC:Source", NULL, false, 32 },
{ 116, "IPTC:CopyrightNotice", "Copyright", false, 128 },
{ 118, "IPTC:Contact", NULL, false, 128 },
{ 120, "IPTC:Caption", "ImageDescription", false, 2000 },
{ 121, "IPTC:LocalCaption", NULL, false, 256 },
{ 122, "IPTC:CaptionWriter", NULL, false, 32 }, // aka Writer/Editor
// Note: 150-154 is audio sampling stuff
{ 184, "IPTC:JobID", NULL, false },
{ 185, "IPTC:MasterDocumentID", NULL, false },
{ 186, "IPTC:ShortDocumentID", NULL, false },
{ 187, "IPTC:UniqueDocumentID", NULL, false },
{ 188, "IPTC:OwnerID", NULL, false },
{ 221, "IPTC:Prefs", NULL, false },
{ 225, "IPTC:ClassifyState", NULL, false },
{ 228, "IPTC:SimilarityIndex", NULL, false },
{ 230, "IPTC:DocumentNotes", NULL, false },
{ 231, "IPTC:DocumentHistory", NULL, false },
{ -1, NULL, NULL, false }
{ 184, "IPTC:JobID", NULL, false, 64 },
{ 185, "IPTC:MasterDocumentID", NULL, false, 256 },
{ 186, "IPTC:ShortDocumentID", NULL, false, 64 },
{ 187, "IPTC:UniqueDocumentID", NULL, false, 128 },
{ 188, "IPTC:OwnerID", NULL, false, 128 },
{ 221, "IPTC:Prefs", NULL, false, 64 },
{ 225, "IPTC:ClassifyState", NULL, false, 64 },
{ 228, "IPTC:SimilarityIndex", NULL, false, 32 },
{ 230, "IPTC:DocumentNotes", NULL, false, 1024 },
{ 231, "IPTC:DocumentHistory", NULL, false, 256 },
{ -1, NULL, NULL, false, 0 }
};

// N.B. All "Date" fields are 8 digit strings: CCYYMMDD
// All "Time" fields are 11 digit strings (what format?)

// IPTC references:
//
// * https://www.iptc.org/std/photometadata/specification/IPTC-PhotoMetadata
// * https://www.iptc.org/std/photometadata/specification/IPTC-PhotoMetadata#iptc-core-schema-1-5-specifications
// This is the one where you can find the length limits
// * ExifTool's documentation about IPTC tags (caveat: not a definitive
// reference, could be outdated or incorrect):
// https://exiftool.org/TagNames/IPTC.html

} // anonymous namespace


Expand Down Expand Up @@ -144,9 +154,13 @@ decode_iptc_iim(const void* iptc, int length, ImageSpec& spec)
} else {
spec.attribute(iimtag[i].name, s);
}
#if 0
// We are no longer confident about auto-translating IPTC
// data into allegedly equivalent metadata.
if (iimtag[i].anothername
&& !spec.extra_attribs.contains(iimtag[i].anothername))
spec.attribute(iimtag[i].anothername, s);
#endif
break;
}
}
Expand Down Expand Up @@ -193,18 +207,28 @@ encode_iptc_iim(const ImageSpec& spec, std::vector<char>& iptc)
Strutil::split(allvals, tokens, ";");
for (auto& token : tokens) {
token = Strutil::strip(token);
if (token.size())
if (token.size()) {
if (iimtag[i].maxlen && iimtag[i].maxlen < token.size())
token = token.substr(0, iimtag[i].maxlen);
encode_iptc_iim_one_tag(iimtag[i].tag, token, iptc);
}
}
} else {
// Regular, non-repeating
encode_iptc_iim_one_tag(iimtag[i].tag, p->get_string(0), iptc);
std::string token = p->get_string(0);
if (iimtag[i].maxlen && iimtag[i].maxlen < token.size())
token = token.substr(0, iimtag[i].maxlen);
encode_iptc_iim_one_tag(iimtag[i].tag, token, iptc);
}
}
#if 0
// We are no longer confident about auto-translating other metadata
// into allegedly equivalent IPTC.
if (iimtag[i].anothername) {
if ((p = spec.find_attribute(iimtag[i].anothername)))
encode_iptc_iim_one_tag(iimtag[i].tag, p->get_string(0), iptc);
}
#endif
}
return iptc.size() != 0;
}
Expand Down
2 changes: 0 additions & 2 deletions testsuite/jpeg-metadata/ref/out.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -83,7 +83,6 @@ with-attribs-and-desc.jpg : 640 x 480, 3 channel, uint8 jpeg
Exif:ColorSpace: 1
Exif:ExifVersion: "0230"
Exif:FlashPixVersion: "0100"
IPTC:Caption: "A photo"
jpeg:subsampling: "4:2:0"
oiio:ColorSpace: "sRGB"
Reading src/blender-render.jpg
Expand All @@ -109,6 +108,5 @@ with-colon-desc.jpg : 640 x 480, 3 channel, uint8 jpeg
Exif:ColorSpace: 1
Exif:ExifVersion: "0230"
Exif:FlashPixVersion: "0100"
IPTC:Caption: "Example:Text"
jpeg:subsampling: "4:2:0"
oiio:ColorSpace: "sRGB"

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