MicroExif: API improvements and minor bugfixes

README.md

@@ -129,6 +129,8 @@ About the image:
   ISO 8601 format without milliseconds (e.g. 2024-03-23T15:30:43). This value
   should be kept unchanged when present.
 - `Description`: A string that describes the subject of the image.
+- `Direction`: Floating-point number indicating the direction of the image
+  when it was captured in degrees (e.g. 123.3).
 - `DocumentName`: The name of the document from which this image was 
   scanned.
 - `HostComputer`: The computer and/or operating system in use at the time 

autotests/write/basic/avif.json

@@ -5,6 +5,10 @@
             "key" : "CreationDate",
             "value" : "2025-01-14T13:53:32+01:00"
         },
+        {
+            "key" : "Direction",
+            "value" : "123.7"
+        },
         {
             "key" : "ModificationDate",
             "value" : "2025-02-14T15:58:44+01:00"

autotests/write/basic/heif.json

@@ -5,6 +5,10 @@
             "key" : "CreationDate",
             "value" : "2025-01-14T13:53:32+01:00"
         },
+        {
+            "key" : "Direction",
+            "value" : "123.7"
+        },
         {
             "key" : "ModificationDate",
             "value" : "2025-02-14T15:58:44+01:00"

autotests/write/basic/jxl.json

@@ -5,6 +5,10 @@
             "key" : "CreationDate",
             "value" : "2025-01-14T13:53:32+01:00"
         },
+        {
+            "key" : "Direction",
+            "value" : "123.7"
+        },
         {
             "key" : "ModificationDate",
             "value" : "2025-02-14T15:58:44+01:00"

autotests/write/basic/jxr.json

@@ -5,6 +5,10 @@
             "key" : "CreationDate",
             "value" : "2025-01-14T13:53:32+01:00"
         },
+        {
+            "key" : "Direction",
+            "value" : "123.7"
+        },
         {
             "key" : "ModificationDate",
             "value" : "2025-02-14T15:58:44+01:00"

src/imageformats/avif.cpp

@@ -534,13 +534,8 @@ bool QAVIFHandler::decode_one_frame()
 
     if (m_decoder->image->exif.size) {
         auto exif = MicroExif::fromRawData(reinterpret_cast<const char *>(m_decoder->image->exif.data), m_decoder->image->exif.size);
-        // set image resolution
+        exif.updateImageResolution(m_current_image);
-        if (exif.horizontalResolution() > 0)
+        exif.updateImageMetadata(m_current_image);
-            m_current_image.setDotsPerMeterX(qRound(exif.horizontalResolution() / 25.4 * 1000));
-        if (exif.verticalResolution() > 0)
-            m_current_image.setDotsPerMeterY(qRound(exif.verticalResolution() / 25.4 * 1000));
-        // set image metadata
-        exif.toImageMetadata(m_current_image);
     }
 
     if (m_decoder->image->xmp.size) {

src/imageformats/heif.cpp

@@ -955,13 +955,8 @@ bool HEIFHandler::ensureDecoder()
                 } else if (isExif) {
                     auto exif = MicroExif::fromByteArray(ba.mid(4));
                     if (!exif.isEmpty()) {
-                        // set image resolution
+                        exif.updateImageResolution(m_current_image);
-                        if (exif.horizontalResolution() > 0)
+                        exif.updateImageMetadata(m_current_image);
-                            m_current_image.setDotsPerMeterX(qRound(exif.horizontalResolution() / 25.4 * 1000));
-                        if (exif.verticalResolution() > 0)
-                            m_current_image.setDotsPerMeterY(qRound(exif.verticalResolution() / 25.4 * 1000));
-                        // set image metadata
-                        exif.toImageMetadata(m_current_image);
                     }
                 }
             }

src/imageformats/jxl.cpp

@@ -791,13 +791,8 @@ bool QJpegXLHandler::decode_one_frame()
 
     if (!m_exif.isEmpty()) {
         auto exif = MicroExif::fromByteArray(m_exif);
-        // set image resolution
+        exif.updateImageResolution(m_current_image);
-        if (exif.horizontalResolution() > 0)
+        exif.updateImageMetadata(m_current_image);
-            m_current_image.setDotsPerMeterX(qRound(exif.horizontalResolution() / 25.4 * 1000));
-        if (exif.verticalResolution() > 0)
-            m_current_image.setDotsPerMeterY(qRound(exif.verticalResolution() / 25.4 * 1000));
-        // set image metadata
-        exif.toImageMetadata(m_current_image);
     }
 
     m_next_image_delay = m_framedelays[m_currentimage_index];

src/imageformats/jxr.cpp

@@ -473,7 +473,7 @@ public:
         }
         auto exif = exifData();
         if (!exif.isEmpty()) {
-            exif.toImageMetadata(image);
+            exif.updateImageMetadata(image);
         }
     }
 

src/imageformats/microexif.cpp

@@ -63,7 +63,8 @@
 #define GPS_LONGITUDE 4
 #define GPS_ALTITUDEREF 5
 #define GPS_ALTITUDE 6
-
+#define GPS_IMGDIRECTIONREF 16
+#define GPS_IMGDIRECTION 17
 #define EXIF_TAG_VALUE(n, byteSize) (((n) << 6) | ((byteSize) & 0x3F))
 #define EXIF_TAG_SIZEOF(dataType) (quint16(dataType) & 0x3F)
 #define EXIF_TAG_DATATYPE(dataType) (quint16(dataType) >> 6)
@@ -152,7 +153,9 @@ static const KnownTags staticGpsTagTypes = {
     TagInfo(GPS_LONGITUDEREF, ExifTagType::Ascii),
     TagInfo(GPS_LONGITUDE, ExifTagType::Rational),
     TagInfo(GPS_ALTITUDEREF, ExifTagType::Byte),
-    TagInfo(GPS_ALTITUDE, ExifTagType::Rational)
+    TagInfo(GPS_ALTITUDE, ExifTagType::Rational),
+    TagInfo(GPS_IMGDIRECTIONREF, ExifTagType::Ascii),
+    TagInfo(GPS_IMGDIRECTION, ExifTagType::Rational)
 };
 // clang-format on
 
@@ -944,6 +947,10 @@ double MicroExif::latitude() const
 
 void MicroExif::setLatitude(double degree)
 {
+    if (qIsNaN(degree)) {
+        m_gpsTags.remove(GPS_LATITUDEREF);
+        m_gpsTags.remove(GPS_LATITUDE);
+    }
     if (degree < -90.0 || degree > 90.0)
         return; // invalid latitude
     auto adeg = qAbs(degree);
@@ -969,6 +976,10 @@ double MicroExif::longitude() const
 
 void MicroExif::setLongitude(double degree)
 {
+    if (qIsNaN(degree)) {
+        m_gpsTags.remove(GPS_LONGITUDEREF);
+        m_gpsTags.remove(GPS_LONGITUDE);
+    }
     if (degree < -180.0 || degree > 180.0)
         return; // invalid longitude
     auto adeg = qAbs(degree);
@@ -983,16 +994,44 @@ double MicroExif::altitude() const
     auto ref = m_gpsTags.value(GPS_ALTITUDEREF);
     if (ref.isNull())
         return qQNaN();
+    if (!m_gpsTags.contains(GPS_ALTITUDE))
+        return qQNaN();
     auto alt = m_gpsTags.value(GPS_ALTITUDE).toDouble();
     return (ref.toInt() == 0 || ref.toInt() == 2) ? alt : -alt;
 }
 
 void MicroExif::setAltitude(double meters)
 {
+    if (qIsNaN(meters)) {
+        m_gpsTags.remove(GPS_ALTITUDEREF);
+        m_gpsTags.remove(GPS_ALTITUDE);
+    }
     m_gpsTags.insert(GPS_ALTITUDEREF, quint8(meters < 0 ? 1 : 0));
     m_gpsTags.insert(GPS_ALTITUDE, meters);
 }
 
+double MicroExif::imageDirection(bool *isMagnetic) const
+{
+    auto tmp = false;
+    if (isMagnetic == nullptr)
+        isMagnetic = &tmp;
+    if (!m_gpsTags.contains(GPS_IMGDIRECTION))
+        return qQNaN();
+    auto ref = gpsString(GPS_IMGDIRECTIONREF).toUpper();
+    *isMagnetic = (ref == QStringLiteral("M"));
+    return m_gpsTags.value(GPS_IMGDIRECTION).toDouble();
+}
+
+void MicroExif::setImageDirection(double degree, bool isMagnetic)
+{
+    if (qIsNaN(degree)) {
+        m_gpsTags.remove(GPS_IMGDIRECTIONREF);
+        m_gpsTags.remove(GPS_IMGDIRECTION);
+    }
+    m_gpsTags.insert(GPS_IMGDIRECTIONREF, isMagnetic ? QStringLiteral("M") : QStringLiteral("T"));
+    m_gpsTags.insert(GPS_IMGDIRECTION, degree);
+}
+
 QByteArray MicroExif::toByteArray(const QDataStream::ByteOrder &byteOrder) const
 {
     QByteArray ba;
@@ -1064,7 +1103,7 @@ bool MicroExif::write(QIODevice *device, const QDataStream::ByteOrder &byteOrder
     return true;
 }
 
-void MicroExif::toImageMetadata(QImage &targetImage, bool replaceExisting) const
+void MicroExif::updateImageMetadata(QImage &targetImage, bool replaceExisting) const
 {
     // set TIFF strings
     for (auto &&p : tiffStrMap) {
@@ -1112,6 +1151,19 @@ void MicroExif::toImageMetadata(QImage &targetImage, bool replaceExisting) const
         if (!qIsNaN(v))
             targetImage.setText(QStringLiteral(META_KEY_LONGITUDE), QStringLiteral("%1").arg(v, 0, 'g', 9));
     }
+    if (replaceExisting || targetImage.text(QStringLiteral(META_KEY_DIRECTION)).isEmpty()) {
+        auto v = imageDirection();
+        if (!qIsNaN(v))
+            targetImage.setText(QStringLiteral(META_KEY_DIRECTION), QStringLiteral("%1").arg(v, 0, 'g', 9));
+    }
+}
+
+void MicroExif::updateImageResolution(QImage &targetImage)
+{
+    if (horizontalResolution() > 0)
+        targetImage.setDotsPerMeterX(qRound(horizontalResolution() / 25.4 * 1000));
+    if (verticalResolution() > 0)
+        targetImage.setDotsPerMeterY(qRound(verticalResolution() / 25.4 * 1000));
 }
 
 MicroExif MicroExif::fromByteArray(const QByteArray &ba)
@@ -1215,6 +1267,9 @@ MicroExif MicroExif::fromImage(const QImage &image)
     auto lon = image.text(QStringLiteral(META_KEY_LONGITUDE)).toDouble(&ok);
     if (ok)
         exif.setLongitude(lon);
+    auto dir = image.text(QStringLiteral(META_KEY_DIRECTION)).toDouble(&ok);
+    if (ok)
+        exif.setImageDirection(dir);
 
     return exif;
 }

src/imageformats/microexif_p.h

@@ -31,8 +31,6 @@
  *
  * This class is a partial (or rather minimal) implementation and is only used
  * to avoid including external libraries when only a few tags are needed.
- *
- * It reads/writes the main IFD only.
  */
 class MicroExif
 {
@@ -251,6 +249,14 @@ public:
     double altitude() const;
     void setAltitude(double meters);
 
+    /*!
+     * \brief imageDirection
+     * \param isMagnetic Set to true if the direction is relative to magnetic north, false if it is relative to true north. Leave nullptr if is not of interest.
+     * \return Floating-point number indicating the direction of the image when it was captured. The range of values is from 0.00 to 359.99 or NaN if not set.
+     */
+    double imageDirection(bool *isMagnetic = nullptr) const;
+    void setImageDirection(double degree, bool isMagnetic = false);
+
     /*!
      * \brief toByteArray
      * Converts the class to RAW data. The raw data contains:
@@ -309,12 +315,19 @@ public:
     bool write(QIODevice *device, const QDataStream::ByteOrder &byteOrder = EXIF_DEFAULT_BYTEORDER) const;
 
     /*!
-     * \brief toImageMetadata
+     * \brief updateImageMetadata
-     * Helper to set metadata in an image.
+     * Helper to set EXIF metadata to the image.
      * \param targetImage The image to set metadata on.
      * \param replaceExisting Replaces any existing metadata.
      */
-    void toImageMetadata(QImage& targetImage, bool replaceExisting = false) const;
+    void updateImageMetadata(QImage &targetImage, bool replaceExisting = false) const;
+
+    /*!
+     * \brief updateImageResolution
+     * Helper to set the EXIF resolution to the image. Resolution is set only if valid.
+     * \param targetImage The image to set resolution on.
+     */
+    void updateImageResolution(QImage &targetImage);
 
     /*!
      * \brief fromByteArray

src/imageformats/psd.cpp

@@ -545,7 +545,7 @@ static bool setExifData(QImage &img, const MicroExif &exif)
 {
     if (exif.isEmpty())
         return false;
-    exif.toImageMetadata(img);
+    exif.updateImageMetadata(img);
     return true;
 }
 

src/imageformats/util_p.h

@@ -20,6 +20,7 @@
 #define META_KEY_COPYRIGHT "Copyright"
 #define META_KEY_CREATIONDATE "CreationDate"
 #define META_KEY_DESCRIPTION "Description"
+#define META_KEY_DIRECTION "Direction"
 #define META_KEY_DOCUMENTNAME "DocumentName"
 #define META_KEY_HOSTCOMPUTER "HostComputer"
 #define META_KEY_LATITUDE "Latitude"