[libcamera-devel] [PATCH 3/3] android: Support initial set of EXIF metadata tags

[Umang Jain]

Support a initial set of  EXIF metadata tags namely:
Make, Model, Height, Width, Orientation and Timestamp.
Each tag is set by a convenient high level helper API
defined in exif.h.

Signed-off-by: Umang Jain <email at uajain.com>
---
 src/android/camera_device.cpp        |  8 +++++++
 src/android/jpeg/encoder_libjpeg.cpp | 12 ++++++++++
 src/android/jpeg/exif.cpp            | 34 ++++++++++++++++++++++++++++
 src/android/jpeg/exif.h              |  8 +++++++
 4 files changed, 62 insertions(+)

diff --git a/src/android/camera_device.cpp b/src/android/camera_device.cpp
index bc5690e..fcf378a 100644
--- a/src/android/camera_device.cpp
+++ b/src/android/camera_device.cpp
@@ -1435,6 +1435,14 @@ void CameraDevice::requestComplete(Request *request)
 		}
 
 		Exif exif;
+		/*
+		 * \todo Discuss setMake String, maybe vendor ID?
+		 * KB suggested to leave it to "libcamera" for now.
+		 * setModel should use the 'model' property of the camera.
+		 */
+		exif.setMake("Libcamera");
+		exif.setModel("cameraModel");
+		exif.setOrientation(orientation_);
 
 		int jpeg_size = encoder->encode(buffer, mapped.maps()[0], &exif);
 		if (jpeg_size < 0) {
diff --git a/src/android/jpeg/encoder_libjpeg.cpp b/src/android/jpeg/encoder_libjpeg.cpp
index 0cd93b6..f84def9 100644
--- a/src/android/jpeg/encoder_libjpeg.cpp
+++ b/src/android/jpeg/encoder_libjpeg.cpp
@@ -213,7 +213,19 @@ int EncoderLibJpeg::encode(const FrameBuffer *source,
 	else
 		compressRGB(&frame);
 
+	exif->setWidth(compress_.image_width);
+	exif->setHeight(compress_.image_height);
+	exif->setTimestamp(source->metadata().timestamp);
+
+	Span<uint8_t> exif_data = exif->generate();
+
 	jpeg_finish_compress(&compress_);
 
+	if (exif->size())
+		/* Store Exif data in the JPEG_APP1 data block. */
+		jpeg_write_marker(&compress_, JPEG_APP0 + 1,
+				  static_cast<const JOCTET *>(exif_data.data()),
+				  exif_data.size());
+
 	return size;
 }
diff --git a/src/android/jpeg/exif.cpp b/src/android/jpeg/exif.cpp
index f6a9f5c..b7591d5 100644
--- a/src/android/jpeg/exif.cpp
+++ b/src/android/jpeg/exif.cpp
@@ -160,6 +160,40 @@ int Exif::setString(ExifIfd ifd, ExifTag tag, ExifFormat format, const std::stri
 	return 0;
 }
 
+int Exif::setHeight(uint16_t height)
+{
+	setShort(EXIF_IFD_0, EXIF_TAG_IMAGE_LENGTH, height);
+	setLong(EXIF_IFD_EXIF, EXIF_TAG_PIXEL_Y_DIMENSION, height);
+
+	return 0;
+}
+
+int Exif::setWidth(uint16_t width)
+{
+	setShort(EXIF_IFD_0, EXIF_TAG_IMAGE_WIDTH, width);
+	setLong(EXIF_IFD_EXIF, EXIF_TAG_PIXEL_X_DIMENSION, width);
+
+	return 0;
+}
+
+int Exif::setTimestamp(const time_t timestamp)
+{
+	std::string ts(std::ctime(&timestamp));
+	int ret = setString(EXIF_IFD_0, EXIF_TAG_DATE_TIME, EXIF_FORMAT_ASCII, ts);
+	if(ret < 0)
+		return ret;
+
+	ret = setString(EXIF_IFD_EXIF, EXIF_TAG_DATE_TIME_ORIGINAL, EXIF_FORMAT_ASCII, ts);
+	if(ret < 0)
+		return ret;
+
+	ret = setString(EXIF_IFD_EXIF, EXIF_TAG_DATE_TIME_DIGITIZED, EXIF_FORMAT_ASCII, ts);
+	if(ret < 0)
+		return ret;
+
+	return ret;
+}
+
 Span<uint8_t> Exif::generate()
 {
 	if (exif_data_) {
diff --git a/src/android/jpeg/exif.h b/src/android/jpeg/exif.h
index 7df83c7..6a8f5f5 100644
--- a/src/android/jpeg/exif.h
+++ b/src/android/jpeg/exif.h
@@ -11,6 +11,7 @@
 
 #include <libcamera/span.h>
 
+#include <ctime>
 #include <string>
 
 class Exif
@@ -24,6 +25,13 @@ public:
 	int setString(ExifIfd ifd, ExifTag tag, ExifFormat format, const std::string &item);
 	int setRational(ExifIfd ifd, ExifTag tag, uint32_t numerator, uint32_t denominator);
 
+	int setHeight(uint16_t height);
+	int setMake(const std::string &make) { return setString(EXIF_IFD_0, EXIF_TAG_MAKE, EXIF_FORMAT_ASCII, make); }
+	int setModel(const std::string &model) { return setString(EXIF_IFD_0, EXIF_TAG_MODEL, EXIF_FORMAT_ASCII, model); }
+	int setOrientation(int orientation) { return setShort(EXIF_IFD_0, EXIF_TAG_ORIENTATION, orientation); }
+	int setTimestamp(const time_t timestamp);
+	int setWidth(uint16_t width);
+
 	libcamera::Span<uint8_t> generate();
 	unsigned char *data() const { return exif_data_; }
 	unsigned int size() const { return size_; }
-- 
2.25.1