[libcamera-devel] [PATCH v2 1/4] android: jpeg: exif: Fix and expand setRational

[Paul Elder]

setRational was not working properly for EXIF tags in the GPS IFD due to
libexif not supporting those tags in exif_entry_initialize().  Manually
specify the size of the EXIF entry to fix this. While at it, add support
for setting multiple rationals, as that is a common use case for
rational EXIF tags.

As Rational types are no longer initialized by libexif directly, the
EXIF_TAG_{X,Y}_RESOLUTION exif tags will not have their default values
populated.

This allows the GPS altitude to be set properly, and is part of the fix
to allow the following CTS test to pass:
- android.hardware.cts.CameraTest#testJpegExif

Signed-off-by: Paul Elder <paul.elder at ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>

---
Changes in v2:
- use span instead of size + array
- expand commit message
---
 src/android/jpeg/exif.cpp | 15 +++++++++++++--
 src/android/jpeg/exif.h   |  2 ++
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/src/android/jpeg/exif.cpp b/src/android/jpeg/exif.cpp
index fdd46070..929ac542 100644
--- a/src/android/jpeg/exif.cpp
+++ b/src/android/jpeg/exif.cpp
@@ -14,6 +14,8 @@
 #include <tuple>
 #include <uchar.h>
 
+#include <libcamera/span.h>
+
 #include "libcamera/internal/log.h"
 #include "libcamera/internal/utils.h"
 
@@ -187,11 +189,20 @@ void Exif::setLong(ExifIfd ifd, ExifTag tag, uint32_t item)
 
 void Exif::setRational(ExifIfd ifd, ExifTag tag, ExifRational item)
 {
-	ExifEntry *entry = createEntry(ifd, tag);
+	setRational(ifd, tag, Span<const ExifRational>{ &item, 1 });
+}
+
+void Exif::setRational(ExifIfd ifd, ExifTag tag, Span<const ExifRational> items)
+{
+	ExifEntry *entry = createEntry(ifd, tag, EXIF_FORMAT_RATIONAL,
+				       items.size(),
+				       items.size() * sizeof(ExifRational));
 	if (!entry)
 		return;
 
-	exif_set_rational(entry->data, order_, item);
+	for (size_t i = 0; i < items.size(); i++)
+		exif_set_rational(entry->data + i * sizeof(ExifRational),
+				  order_, items[i]);
 	exif_entry_unref(entry);
 }
 
diff --git a/src/android/jpeg/exif.h b/src/android/jpeg/exif.h
index b0d61402..8aa1b123 100644
--- a/src/android/jpeg/exif.h
+++ b/src/android/jpeg/exif.h
@@ -89,6 +89,8 @@ private:
 		       const std::string &item,
 		       StringEncoding encoding = NoEncoding);
 	void setRational(ExifIfd ifd, ExifTag tag, ExifRational item);
+	void setRational(ExifIfd ifd, ExifTag tag,
+			 libcamera::Span<const ExifRational> items);
 
 	std::tuple<int, int, int> degreesToDMS(double decimalDegrees);
 	void setGPSDMS(ExifIfd ifd, ExifTag tag, int deg, int min, int sec);
-- 
2.27.0