Merge pull request #1759 from alicevision/dev/focalLength

[sfmData] ImageInfo: Add support for ARRI- and DJI-specific focal length metadata
alicevision · Oct 16, 2024 · f784cd3 · f784cd3
2 parents 11efc39 + 8d519a3
commit f784cd3
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Showing 2 changed files with 78 additions and 31 deletions.
diff --git a/src/aliceVision/sfmData/ImageInfo.cpp b/src/aliceVision/sfmData/ImageInfo.cpp
@@ -395,5 +395,82 @@ int ImageInfo::getSensorSize(const std::vector<sensorDB::Datasheet>& sensorDatab
     return errCode;
 }
 
+double ImageInfo::getMetadataFocalLength() const
+{
+    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)
+        {
+            ALICEVISION_LOG_DEBUG("Used Sony metadata 'LensZoomActualFocalLength'. The retrieved focal length ("
+                                    << focalLength << ") is in meters and will be multiplied by 1000.");
+            focalLength *= 1000;
+        }
+    }
+
+    // 32767 = (2^15 - 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 == USHRT_MAX || focalLength == SHRT_MAX || focalLength == UINT_MAX || focalLength == INT_MAX || focalLength == 4294970)
+    {
+        focalLength = -1;
+    }
+
+    // For DJI drones, the focal length may be expressed as a list (e.g. [50000,1000])
+    std::string focalLengthList = getMetadata({"focal_length"});
+    std::string focalLengthStr = "";
+    std::string focalLengthDividerStr = "";
+
+    if (!focalLengthList.empty() && focalLengthList.find("[") == 0 && focalLengthList.find("]") == focalLengthList.size() - 1)
+    {
+        ALICEVISION_LOG_DEBUG("Used DJI drones metadata 'focal_length'. The retrieved focal length ("
+                                << focalLengthList << ") will have its first term divided by its second term.");
+        std::size_t delimiterPosition = focalLengthList.find(",");
+        if (delimiterPosition != std::string::npos)
+        {
+            focalLengthStr = focalLengthList.substr(1, delimiterPosition - 1);
+            focalLengthDividerStr = focalLengthList.substr(delimiterPosition + 1, focalLengthList.size() - delimiterPosition - 2);
+        }
+
+        // Focal length is provided in µm, hence the required division
+        double uf = 0.0;
+        bool valid = true;
+
+        try
+        {
+            uf = std::stod(focalLengthStr) / std::stod(focalLengthDividerStr);
+        }
+        catch(const std::exception& e)
+        {
+            valid = false;
+        }
+
+        if (valid) 
+        {
+            focalLength = uf;
+        }
+    }
+
+    // Might be available and more precise (especially if the focal length was initially retrieved from a string)
+    double nominalFocalLength = getDoubleMetadata({"AxialNominalFocalLength", "axialNominalFocalLength"});
+    if (nominalFocalLength != -1)
+    {
+        ALICEVISION_LOG_DEBUG("Used ARRI metadata 'AxialNominalFocalLength'. The retrieved focal length ("
+                                << nominalFocalLength << ") will need to be converted from mm or µm.");
+        // For ARRI camera, the axial nominal focal length might either be available as mm or µm.
+        // We assume that if the result is larger than 9999, then the unit cannot be mm
+        if (nominalFocalLength > 9999)
+        {
+            nominalFocalLength /= 1000;
+        }
+        focalLength = nominalFocalLength;
+    }
+
+    return focalLength;
+}
+
 }  // namespace sfmData
 }  // namespace aliceVision
diff --git a/src/aliceVision/sfmData/ImageInfo.hpp b/src/aliceVision/sfmData/ImageInfo.hpp
@@ -198,37 +198,7 @@ class ImageInfo
      * @brief Get the corresponding "FocalLength" metadata value
      * @return the metadata value float or -1 if no corresponding value
      */
-    double getMetadataFocalLength() const
-    {
-        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 = (2^15 - 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 == USHRT_MAX || focalLength == SHRT_MAX || focalLength == UINT_MAX || focalLength == INT_MAX || 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;
-    }
+    double getMetadataFocalLength() const;
 
     /**
      * @brief Get the corresponding "ExposureTime" (shutter) metadata value