fix: IPTC fields have length limits

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]>
AcademySoftwareFoundation · lgritz · Dec 28, 2024 · Dec 23, 2024 · Dec 27, 2024 · Dec 23, 2024
commit 023cebbf3455a4c3b9242695610873748e340b72
diff --git a/src/doc/stdmetadata.rst b/src/doc/stdmetadata.rst
@@ -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
 
@@ -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.
@@ -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.
@@ -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.
@@ -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

diff --git a/src/libOpenImageIO/iptc.cpp b/src/libOpenImageIO/iptc.cpp
@@ -21,63 +21,64 @@ 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
@@ -144,9 +145,13 @@ 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;
                 }
             }
@@ -193,18 +198,28 @@ 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;
 }

diff --git a/testsuite/jpeg-metadata/ref/out.txt b/testsuite/jpeg-metadata/ref/out.txt
@@ -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
@@ -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"