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Improved EXIF V3 compatibility

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EXIF specs V3 added the UTF-8 data type. The MicroExif class now allows serializations to choose whether to support the V2 or V3 format. To maximize compatibility with old readers, even when V3 is set, the ASCII data type is used if possible.

The JXR plugin, based on TIFF V6 container, does not allow to use the V3 format (it does not recognize the UTF-8 data type) and therefore V2 has been forced. For all other plugins using MicroExif, it is now possible to save, e.g., descriptions in Japanese.

Please note that this patch is also a bugfix: when saving, version 3 was set but the strings were always saved as ASCII.
This commit is contained in:
Mirco Miranda
2025-04-18 13:53:12 +00:00
committed by Albert Astals Cid
parent 9c47845f15
commit ae62ea3dfc
6 changed files with 80 additions and 39 deletions
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src/imageformats/microexif.cpp
+56 -28
View File
@@ -111,17 +111,17 @@ static const KnownTags staticTagTypes = {
TagInfo(TIFF_IMAGEWIDTH, ExifTagType::Long),
TagInfo(TIFF_IMAGEHEIGHT, ExifTagType::Long),
TagInfo(TIFF_BITSPERSAMPLE, ExifTagType::Short),
TagInfo(TIFF_IMAGEDESCRIPTION, ExifTagType::Ascii),
TagInfo(TIFF_MAKE, ExifTagType::Ascii),
TagInfo(TIFF_MODEL, ExifTagType::Ascii),
TagInfo(TIFF_IMAGEDESCRIPTION, ExifTagType::Utf8),
TagInfo(TIFF_MAKE, ExifTagType::Utf8),
TagInfo(TIFF_MODEL, ExifTagType::Utf8),
TagInfo(TIFF_ORIENT, ExifTagType::Short),
TagInfo(TIFF_XRES, ExifTagType::Rational),
TagInfo(TIFF_YRES, ExifTagType::Rational),
TagInfo(TIFF_URES, ExifTagType::Short),
TagInfo(TIFF_SOFTWARE, ExifTagType::Ascii),
TagInfo(TIFF_ARTIST, ExifTagType::Ascii),
TagInfo(TIFF_SOFTWARE, ExifTagType::Utf8),
TagInfo(TIFF_ARTIST, ExifTagType::Utf8),
TagInfo(TIFF_DATETIME, ExifTagType::Ascii),
TagInfo(TIFF_COPYRIGHT, ExifTagType::Ascii),
TagInfo(TIFF_COPYRIGHT, ExifTagType::Utf8),
TagInfo(EXIF_EXIFIFD, ExifTagType::Long),
TagInfo(EXIF_GPSIFD, ExifTagType::Long),
TagInfo(EXIF_DATETIMEORIGINAL, ExifTagType::Ascii),
@@ -134,10 +134,10 @@ static const KnownTags staticTagTypes = {
TagInfo(EXIF_PIXELYDIM, ExifTagType::Long),
TagInfo(EXIF_IMAGEUNIQUEID, ExifTagType::Ascii),
TagInfo(EXIF_BODYSERIALNUMBER, ExifTagType::Ascii),
TagInfo(EXIF_LENSMAKE, ExifTagType::Ascii),
TagInfo(EXIF_LENSMODEL, ExifTagType::Ascii),
TagInfo(EXIF_LENSMAKE, ExifTagType::Utf8),
TagInfo(EXIF_LENSMODEL, ExifTagType::Utf8),
TagInfo(EXIF_LENSSERIALNUMBER, ExifTagType::Ascii),
TagInfo(EXIF_IMAGETITLE, ExifTagType::Ascii),
TagInfo(EXIF_IMAGETITLE, ExifTagType::Utf8),
TagInfo(EXIF_EXIFVERSION, ExifTagType::Undefined)
};
// clang-format on
@@ -367,6 +367,30 @@ static void writeData(QDataStream &ds, const QVariant &value, const ExifTagType&
}
}
static ExifTagType updateDataType(const ExifTagType &dataType, const QVariant &value, const MicroExif::Version &ver)
{
if (dataType != ExifTagType::Utf8)
return dataType;
if (ver == MicroExif::V2)
return ExifTagType::Ascii;
// Note that in EXIF specs, UTF-8 is backward compatible with ASCII: all UTF-8 tags can also be ASCII.
// To maximize compatibility, I check if the string can be encoded in ASCII.
auto txt = value.toString();
// I try to implement a rudimentary check without going through Qt's string conversion classes:
// a UTF-8 string if it uses only characters in the first 127 of the ASCII table is encoded as
// a Latin 1. Each character above 128, whether it is an extended ASCII character or a character
// of another nature, uses 2 or more bytes. Since the EXIF ​​specifications state that the ASCII
// type must use only the first 127 characters, I only need to do the size comparison to understand
// which type to use.
if (txt.toLatin1().size() == txt.toUtf8().size())
return ExifTagType::Ascii;
return dataType;
}
/*!
* \brief writeIfd
* \param ds The stream.
@@ -375,7 +399,12 @@ static void writeData(QDataStream &ds, const QVariant &value, const ExifTagType&
* \param knownTags List of known and supported tags.
* \return True on success, otherwise false.
*/
static bool writeIfd(QDataStream &ds, const MicroExif::Tags &tags, TagPos &positions, quint32 pos = 0, const KnownTags &knownTags = staticTagTypes)
static bool writeIfd(QDataStream &ds,
const MicroExif::Version &ver,
const MicroExif::Tags &tags,
TagPos &positions,
quint32 pos = 0,
const KnownTags &knownTags = staticTagTypes)
{
if (tags.isEmpty())
return true;
@@ -390,7 +419,7 @@ static bool writeIfd(QDataStream &ds, const MicroExif::Tags &tags, TagPos &posit
continue;
}
auto value = tags.value(key);
auto dataType = knownTags.value(key);
auto dataType = updateDataType(knownTags.value(key), value, ver);
auto count = countBytes(dataType, value);
ds << quint16(key);
@@ -412,9 +441,8 @@ static bool writeIfd(QDataStream &ds, const MicroExif::Tags &tags, TagPos &posit
if (!knownTags.contains(key)) {
continue;
}
auto value = tags.value(key);
auto dataType = knownTags.value(key);
auto dataType = updateDataType(knownTags.value(key), value, ver);
auto count = countBytes(dataType, value);
auto valueSize = count * EXIF_TAG_SIZEOF(dataType);
if (valueSize <= 4)
@@ -1032,7 +1060,7 @@ void MicroExif::setImageDirection(double degree, bool isMagnetic)
m_gpsTags.insert(GPS_IMGDIRECTION, degree);
}
QByteArray MicroExif::toByteArray(const QDataStream::ByteOrder &byteOrder) const
QByteArray MicroExif::toByteArray(const QDataStream::ByteOrder &byteOrder, const Version &version) const
{
QByteArray ba;
{
@@ -1043,16 +1071,16 @@ QByteArray MicroExif::toByteArray(const QDataStream::ByteOrder &byteOrder) const
return ba;
}
QByteArray MicroExif::exifIfdByteArray(const QDataStream::ByteOrder &byteOrder) const
QByteArray MicroExif::exifIfdByteArray(const QDataStream::ByteOrder &byteOrder, const Version &version) const
{
QByteArray ba;
{
QDataStream ds(&ba, QIODevice::WriteOnly);
ds.setByteOrder(byteOrder);
auto exifTags = m_exifTags;
exifTags.insert(EXIF_EXIFVERSION, QByteArray("0300"));
exifTags.insert(EXIF_EXIFVERSION, version == Version::V3 ? QByteArray("0300") : QByteArray("0232"));
TagPos positions;
if (!writeIfd(ds, exifTags, positions))
if (!writeIfd(ds, version, exifTags, positions))
return {};
}
return ba;
@@ -1065,7 +1093,7 @@ bool MicroExif::setExifIfdByteArray(const QByteArray &ba, const QDataStream::Byt
return readIfd(ds, m_exifTags, 0, staticTagTypes);
}
QByteArray MicroExif::gpsIfdByteArray(const QDataStream::ByteOrder &byteOrder) const
QByteArray MicroExif::gpsIfdByteArray(const QDataStream::ByteOrder &byteOrder, const Version &version) const
{
QByteArray ba;
{
@@ -1074,7 +1102,7 @@ QByteArray MicroExif::gpsIfdByteArray(const QDataStream::ByteOrder &byteOrder) c
auto gpsTags = m_gpsTags;
gpsTags.insert(GPS_GPSVERSION, QByteArray("2400"));
TagPos positions;
if (!writeIfd(ds, gpsTags, positions, 0, staticGpsTagTypes))
if (!writeIfd(ds, version, gpsTags, positions, 0, staticGpsTagTypes))
return {};
return ba;
}
@@ -1087,7 +1115,7 @@ bool MicroExif::setGpsIfdByteArray(const QByteArray &ba, const QDataStream::Byte
return readIfd(ds, m_gpsTags, 0, staticGpsTagTypes);
}
bool MicroExif::write(QIODevice *device, const QDataStream::ByteOrder &byteOrder) const
bool MicroExif::write(QIODevice *device, const QDataStream::ByteOrder &byteOrder, const Version &version) const
{
if (device == nullptr || device->isSequential() || isEmpty())
return false;
@@ -1096,7 +1124,7 @@ bool MicroExif::write(QIODevice *device, const QDataStream::ByteOrder &byteOrder
ds.setByteOrder(byteOrder);
if (!writeHeader(ds))
return false;
if (!writeIfds(ds))
if (!writeIfds(ds, version))
return false;
}
device->close();
@@ -1327,30 +1355,30 @@ bool MicroExif::writeHeader(QDataStream &ds) const
return ds.status() == QDataStream::Ok;
}
bool MicroExif::writeIfds(QDataStream &ds) const
bool MicroExif::writeIfds(QDataStream &ds, const Version &version) const
{
auto tiffTags = m_tiffTags;
auto exifTags = m_exifTags;
auto gpsTags = m_gpsTags;
updateTags(tiffTags, exifTags, gpsTags);
updateTags(tiffTags, exifTags, gpsTags, version);
TagPos positions;
if (!writeIfd(ds, tiffTags, positions))
if (!writeIfd(ds, version, tiffTags, positions))
return false;
if (!writeIfd(ds, exifTags, positions, positions.value(EXIF_EXIFIFD)))
if (!writeIfd(ds, version, exifTags, positions, positions.value(EXIF_EXIFIFD)))
return false;
if (!writeIfd(ds, gpsTags, positions, positions.value(EXIF_GPSIFD), staticGpsTagTypes))
if (!writeIfd(ds, version, gpsTags, positions, positions.value(EXIF_GPSIFD), staticGpsTagTypes))
return false;
return true;
}
void MicroExif::updateTags(Tags &tiffTags, Tags &exifTags, Tags &gpsTags) const
void MicroExif::updateTags(Tags &tiffTags, Tags &exifTags, Tags &gpsTags, const Version &version) const
{
if (exifTags.isEmpty()) {
tiffTags.remove(EXIF_EXIFIFD);
} else {
tiffTags.insert(EXIF_EXIFIFD, quint32());
exifTags.insert(EXIF_EXIFVERSION, QByteArray("0300"));
exifTags.insert(EXIF_EXIFVERSION, version == Version::V3 ? QByteArray("0300") : QByteArray("0232"));
}
if (gpsTags.isEmpty()) {
tiffTags.remove(EXIF_GPSIFD);