fix(exif): Support EXIF 3.0 tags

We were supporting Exif 2.3, but in 2024, Exif 3.0 was published and
it adds some more tags for us to recognize.

The only part I am not sure about here is that the ExifVersion we
output is still marked as 2.3, not 3.0, because I'm worried that if we
mark it as 3.0, older software reading the images will reject
it. Let's see what happens. If downstream apps care, maybe we can bump
to 3.0, or even bump to 3.0 only if any of the 3.0 tags are used (that
is more involved).

Signed-off-by: Larry Gritz <[email protected]>

Author: lgritz

src/doc/stdmetadata.rst

@@ -760,6 +760,59 @@ A sum of:
     A unique identifier for the image, as 16 ASCII hexadecimal digits
     representing a 128-bit number.
 
+.. option:: "Exif:ImageTitle" : string
+
+    Title of the image.
+
+.. option:: "Exif:Photographer" : string
+
+    The name of the photographer. This may be different from the "Artist"
+    field.
+
+.. option:: "Exif:ImageEdtor" : string
+
+    The name of the main person who edited the image.
+
+.. option:: "Exif:CameraFirmware" : string
+
+    The name and version of the firmware of the camera that captured the image.
+
+.. option:: "Exif:RAWDevelopingSoftware" : string
+
+    The name and version of the software that developed the RAW image.
+
+.. option:: "Exif:ImageEditingSoftware" : string
+
+    The name and version of any image editing software that was used to
+    process or edit the image.
+
+.. option:: "Exif:MetadataEditingSoftware" : string
+
+    The name and version of any image editing software that was used to
+    edit the image metadata but not the pixels.
+
+.. option:: "Exif:CompositeImage" : int
+
+    Indicates whether the recorded image is a composite image (generated
+    from capturing multiple, tentatively recorded, source images).
+
+    ===  ==============================================================
+     0   unknown
+     1   non-composite image
+     2   general composite image
+     3   composite image captured when shooting
+    ===  ==============================================================
+
+.. option:: "Exif:SourceImageNumberOfCompositeImage" : ushort[2]
+
+    If a composite image, the first value is the number of source images
+    captured (at least 2) and the second value is the number of those
+    source images ultimately used in the comopsite image.
+
+.. option:: "Exif:SourceImageExposureTimesOfCompositeImage"
+
+    This is currently unsupported by OpenImageIO.
+
 
 
 GPS Exif metadata

src/include/OpenImageIO/tiffutils.h

@@ -45,6 +45,14 @@ struct TIFFDirEntry {
 
 OIIO_NAMESPACE_BEGIN
 
+// Exif spec extends TIFFDataType beyond what TIFF or litiff define in
+// TIFFDataType.
+enum TIFFDataType_Exif3_Extensions {
+    EXIF_UTF8_TYPE = 129
+};
+
+
+
 // Define EXIF constants
 enum TIFFTAG {
     EXIF_EXPOSURETIME               = 33434,
@@ -128,6 +136,16 @@ enum TIFFTAG {
     EXIF_LENSMODEL                  = 42036,
     EXIF_LENSSERIALNUMBER           = 42037,
     EXIF_GAMMA                      = 42240,
+    EXIF_IMAGETITLE                 = 42038,
+    EXIF_PHOTOGRAPHER               = 42039,
+    EXIF_IMAGEEDTOR                 = 42040,
+    EXIF_CAMERAFIRMWARE             = 42041,
+    EXIF_RAWDEVELOPINGSOFTWARE      = 42042,
+    EXIF_IMAGEEDITINGSOFTWARE       = 42043,
+    EXIF_METADATAEDITINGSOFTWARE    = 42044,
+    EXIF_COMPOSITEIMAGE             = 42080,
+    EXIF_SOURCEIMAGENUMBEROFCOMPOSITEIMAGE        = 42080,
+    EXIF_SOURCEIMAGEEXPOSURETIMESOFCOMPOSITEIMAGE = 42080,
 };
 
 OIIO_NAMESPACE_END

src/libOpenImageIO/exif.cpp

@@ -260,6 +260,7 @@ print_dir_entry(std::ostream& out, const TagMap& tagmap,
 
     switch (dir.tdir_type) {
     case TIFF_ASCII:
+    case EXIF_TIFF_UTF8:
         OIIO::print(out, "'{}'", string_view(mydata, dir.tdir_count));
         break;
     case TIFF_RATIONAL: {
@@ -522,7 +523,17 @@ static const TagInfo exif_tag_table[] = {
     { EXIF_LENSMAKE,  "Exif:LensMake",         TIFF_ASCII, 0 },
     { EXIF_LENSMODEL,  "Exif:LensModel",        TIFF_ASCII, 0 },
     { EXIF_LENSSERIALNUMBER,  "Exif:LensSerialNumber", TIFF_ASCII, 0 },
-    { EXIF_GAMMA,  "Exif:Gamma", TIFF_RATIONAL, 0 }
+    { EXIF_GAMMA,  "Exif:Gamma", TIFF_RATIONAL, 0 },
+    { EXIF_IMAGETITLE, "Exif:ImageTitle", TIFF_ASCII, 0 },
+    { EXIF_PHOTOGRAPHER, "Exif:Photographer", TIFF_ASCII, 0 },
+    { EXIF_IMAGEEDTOR, "Exif:ImageEdtor", TIFF_ASCII, 0 },
+    { EXIF_CAMERAFIRMWARE, "Exif:CameraFirmware", TIFF_ASCII, 0 },
+    { EXIF_RAWDEVELOPINGSOFTWARE, "Exif:RAWDevelopingSoftware", TIFF_ASCII, 0 },
+    { EXIF_IMAGEEDITINGSOFTWARE, "Exif:ImageEditingSoftware", TIFF_ASCII, 0 },
+    { EXIF_METADATAEDITINGSOFTWARE, "Exif:MetadataEditingSoftware", TIFF_ASCII, 0 },
+    { EXIF_COMPOSITEIMAGE, "Exif:CompositeImage", TIFF_SHORT, 1 },
+    { EXIF_SOURCEIMAGENUMBEROFCOMPOSITEIMAGE, "Exif:SourceImageNumberOfCompositeImage", TIFF_SHORT, 2 },
+    { EXIF_SOURCEIMAGEEXPOSURETIMESOFCOMPOSITEIMAGE, "Exif:SourceImageExposureTimesOfCompositeImage", TIFF_NOTYPE, 0 },
     // clang-format on
 };
 
@@ -742,7 +753,7 @@ add_exif_item_to_spec(ImageSpec& spec, const char* name,
             spec.attribute(name, TypeDesc(TypeDesc::FLOAT, int(count)), f);
         return;
     }
-    if (dirp->tdir_type == TIFF_ASCII) {
+    if (dirp->tdir_type == TIFF_ASCII || dirp->tdir_type == EXIF_UTF8_TYPE) {
         size_t len           = tiff_data_size(*dirp);
         cspan<uint8_t> dspan = pvt::dataspan<char>(*dirp, buf,
                                                    offset_adjustment, len);
@@ -1393,6 +1404,8 @@ encode_exif(const ImageSpec& spec, std::vector<char>& blob,
         // Add some required Exif tags that wouldn't be in the spec
         append_tiff_dir_entry(exifdirs, blob, EXIF_EXIFVERSION, TIFF_UNDEFINED,
                               4, as_bytes("0230", 4), tiffstart, 0, endianreq);
+        // NOTE: We are still saying we write Exif 2.3 even though we support
+        // the additional 3.0 tags.
         append_tiff_dir_entry(exifdirs, blob, EXIF_FLASHPIXVERSION,
                               TIFF_UNDEFINED, 4, as_bytes("0100", 4), tiffstart,
                               0, endianreq);

src/libOpenImageIO/exif.h

@@ -22,6 +22,9 @@
 #define DEBUG_EXIF_UNHANDLED 0
 
 
+// Exif Documentation:
+//   - https://archive.org/details/exif-specs-3.0-dc-008-translation-2023-e
+
 
 OIIO_NAMESPACE_BEGIN
 namespace pvt {

src/libOpenImageIO/xmp.cpp

@@ -317,7 +317,7 @@ add_attrib(ImageSpec& spec, string_view xmlname, string_view xmlvalue,
                  && count == 1) {
             oiiotype = TypeDesc::FLOAT;
             special  = Rational;
-        } else if (tifftype == TIFF_ASCII)
+        } else if (tifftype == TIFF_ASCII || tifftype == EXIF_UTF8_TYPE)
             oiiotype = TypeDesc::STRING;
         else if (tifftype == TIFF_BYTE && count == 1)
             oiiotype = TypeDesc::INT;