android: jpeg: post_processor_jpeg: Embed thumbnail into Exif metadata

Embed a Jpeg-encoded thumbnail into Exif metadata using the Thumbnailer
class that got introduced.

Introduce a helper function in Exif class for setting the thumbnail
data.

Signed-off-by: Umang Jain <email@uajain.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
[Kieran: Add todo comment, and Compression enum]
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

1 files changed, 23 insertions, 1 deletions

diff --git a/src/android/jpeg/exif.cpp b/src/android/jpeg/exif.cpp
index d21534a4..33b3fa7f 100644
--- a/src/android/jpeg/exif.cpp
+++ b/src/android/jpeg/exif.cpp
@@ -75,8 +75,16 @@ Exif::~Exif()
 	if (exifData_)
 		free(exifData_);
 
-	if (data_)
+	if (data_) {
+		/*
+		 * Reset thumbnail data to avoid getting double-freed by
+		 * libexif. It is owned by the caller (i.e. PostProcessorJpeg).
+		 */
+		data_->data = nullptr;
+		data_->size = 0;
+
 		exif_data_unref(data_);
+	}
 
 	if (mem_)
 		exif_mem_unref(mem_);
@@ -268,6 +276,20 @@ void Exif::setOrientation(int orientation)
 	setShort(EXIF_IFD_0, EXIF_TAG_ORIENTATION, value);
 }
 
+/*
+ * The thumbnail data should remain valid until the Exif object is destroyed.
+ * Failing to do so, might result in no thumbnail data being set even after a
+ * call to Exif::setThumbnail().
+ */
+void Exif::setThumbnail(Span<const unsigned char> thumbnail,
+			Compression compression)
+{
+	data_->data = const_cast<unsigned char *>(thumbnail.data());
+	data_->size = thumbnail.size();
+
+	setShort(EXIF_IFD_0, EXIF_TAG_COMPRESSION, compression);
+}
+
 [[nodiscard]] int Exif::generate()
 {
 	if (exifData_) {