[sfmData] Retrieve focal length from metadata for specific cameras

For ARRI, RED and Sony cameras, the focal length information might be
located at an unsual place in the metadata, or provided with another unit
than millimeters.

This commit ensures we retrieve it if it is available, and convert it
to the correct unit.

src/aliceVision/sfmData/imageInfo.cpp

@@ -254,11 +254,23 @@ int ImageInfo::getSensorSize(const std::vector<sensorDB::Datasheet>& sensorDatab
     }
 
     // try to find / compute with 'FocalLengthIn35mmFilm' metadata
-    const bool hasFocalIn35mmMetadata = hasDigitMetadata({"Exif:FocalLengthIn35mmFilm", "FocalLengthIn35mmFilm"});
+    const bool hasFocalIn35mmMetadata = hasDigitMetadata({
+        "Exif:FocalLengthIn35mmFilm",
+        "FocalLengthIn35mmFilm",
+        "LensZoom35mmStillCameraEquivalent"
+    });
+
     if (hasFocalIn35mmMetadata)
     {
         const double diag24x36 = std::sqrt(36.0 * 36.0 + 24.0 * 24.0);
-        const double focalIn35mm = hasFocalIn35mmMetadata ? getDoubleMetadata({"Exif:FocalLengthIn35mmFilm", "FocalLengthIn35mmFilm"}) : -1.0;
+
+        double focalIn35mm = getDoubleMetadata({"Exif:FocalLengthIn35mmFilm", "FocalLengthIn35mmFilm"});
+        if (focalIn35mm == -1)
+        {
+            // Info not available in the "classic" metadata, look for the one that's specific to Sony.
+            // Sony metadata: the 35mm focal length equivalent is provided in meters.
+            focalIn35mm = getDoubleMetadata({"LensZoom35mmStillCameraEquivalent"}) * 1000;
+        }
 
         if (sensorWidth == -1.0)
         {
@@ -274,7 +286,7 @@ int ImageInfo::getSensorSize(const std::vector<sensorDB::Datasheet>& sensorDatab
             }
             else
             {
-                // no sensorWidth and no focalLength but valid focalLengthIn35mm, so consider sensorWith
+                // no sensorWidth and no focalLength but valid focalLengthIn35mm, so consider sensorWidth
                 // as 35mm
                 sensorWidth = diag24x36 * std::sqrt(1.0 / (1.0 + invRatio * invRatio));
                 focalLengthmm = sensorWidth * (focalIn35mm) / 36.0;
@@ -316,6 +328,22 @@ int ImageInfo::getSensorSize(const std::vector<sensorDB::Datasheet>& sensorDatab
         }
     }
 
+    // If available, effective sensor width and height are provided in µm (Sony)
+    const double effectiveSensorWidth = getDoubleMetadata({ "ImageSensorEffectiveWidth" });
+    const double effectiveSensorHeight = getDoubleMetadata({ "ImageSensorEffectiveHeight "});
+
+    // If no sensor width has been found or computed yet and the effective sensor width is available, then use it
+    const bool effectiveSensorSizeApplied = effectiveSensorWidth != -1.0 && sensorWidth == -1.0;
+    if (effectiveSensorSizeApplied)
+    {
+        sensorWidth = effectiveSensorWidth / 1000.0;
+        if (effectiveSensorHeight != -1.0)
+        {
+            sensorHeight = effectiveSensorHeight / 1000.0;
+        }
+        sensorWidthSource = ESensorWidthSource::FROM_METADATA_ESTIMATION;
+    }
+
     // error handling
     if (sensorWidth == -1.0)
     {
@@ -369,7 +397,7 @@ int ImageInfo::getSensorSize(const std::vector<sensorDB::Datasheet>& sensorDatab
         sensorWidth = 36.0;
         sensorHeight = 24.0;
     }
-    else
+    else if (sensorHeight == -1.0)  // If the sensor height has already been set with the effective height, don't overwrite it
     {
         sensorHeight = (imageRatio > 1.0) ? sensorWidth / imageRatio : sensorWidth * imageRatio;
     }

src/aliceVision/sfmData/imageInfo.hpp

@@ -183,7 +183,8 @@ class ImageInfo
      */
     const std::string& getMetadataModel() const
     {
-        return getMetadata({"Model", "cameraModel", "cameraModelName", "camera model", "camera model name"});
+        return getMetadata({"Model", "cameraModel", "cameraModelName", "CameraModel",
+                            "camera model", "camera_model", "camera model name"});
     }
 
     /**
@@ -219,7 +220,7 @@ class ImageInfo
      */
     const std::string& getMetadataLensSerialNumber() const
     {
-        return getMetadata({ "Exif:LensSerialNumber", "lensSerialNumber", "lens serial number" });
+        return getMetadata({ "Exif:LensSerialNumber", "lensSerialNumber", "lens serial number", "lens_serial_number" });
     }
 
     /**
@@ -228,7 +229,34 @@ class ImageInfo
      */
     double getMetadataFocalLength() const
     {
-        return getDoubleMetadata({"Exif:FocalLength", "focalLength", "focal length"});
+        double focalLength = getDoubleMetadata({"Exif:FocalLength", "focalLength", "focal length", "lens_focal_length"});
+
+        if (focalLength == -1)
+        {
+            // Sony metadata: the focal length is provided in meters
+            focalLength = getDoubleMetadata({"LensZoomActualFocalLength"});
+            if (focalLength != -1)
+            {
+                focalLength *= 1000;
+            }
+        }
+
+        // 32767 = (2^16 - 1) - Maximum of a signed short: means there is no available focal length
+        // 4294967295 = (2^32 - 1) - Maximum of a signed integer: means there is no available focal length
+        //   -> might be truncated and/or rounded up to 4.29497e+06
+        else if (focalLength == SHRT_MAX - 1 || focalLength == UINT_MAX - 1 || focalLength == 4294970)
+        {
+            focalLength = -1;
+        }
+
+        // Might be available and more precise (especially if the focal length was initially retrieved from a string)
+        double nominativeFocalLength = getDoubleMetadata({"AxialNominalFocalLength"});
+        if (nominativeFocalLength != -1)
+        {
+            focalLength = nominativeFocalLength;
+        }
+
+        return focalLength;
     }
 
     /**