android: jpeg: Support an initial set of EXIF metadata tags

Create a Exif object with various metadata tags set, just before
the encoder starts to encode the frame. The object is passed
directly as libcamera::Span<> to make sure EXIF tags can be set
in a single place i.e. in CameraDevice and the encoder only has
the job to write the data in the final output.

Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Signed-off-by: Umang Jain <email@uajain.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

src/android/camera_device.cpp

@@ -24,6 +24,7 @@
 #include "system/graphics.h"
 
 #include "jpeg/encoder_libjpeg.h"
+#include "jpeg/exif.h"
 
 using namespace libcamera;
 
@@ -1439,7 +1440,23 @@ void CameraDevice::requestComplete(Request *request)
 			continue;
 		}
 
-		int jpeg_size = encoder->encode(buffer, mapped.maps()[0]);
+		/* Set EXIF metadata for various tags. */
+		Exif exif;
+		/* \todo Set Make and Model from external vendor tags. */
+		exif.setMake("libcamera");
+		exif.setModel("cameraModel");
+		exif.setOrientation(orientation_);
+		exif.setSize(cameraStream->size);
+		/*
+		 * We set the frame's EXIF timestamp as the time of encode.
+		 * Since the precision we need for EXIF timestamp is only one
+		 * second, it is good enough.
+		 */
+		exif.setTimestamp(std::time(nullptr));
+		if (exif.generate() != 0)
+			LOG(HAL, Error) << "Failed to generate valid EXIF data";
+
+		int jpeg_size = encoder->encode(buffer, mapped.maps()[0], exif.data());
 		if (jpeg_size < 0) {
 			LOG(HAL, Error) << "Failed to encode stream image";
 			status = CAMERA3_BUFFER_STATUS_ERROR;

src/android/jpeg/encoder.h

@@ -18,7 +18,8 @@ public:
 
 	virtual int configure(const libcamera::StreamConfiguration &cfg) = 0;
 	virtual int encode(const libcamera::FrameBuffer *source,
-			   const libcamera::Span<uint8_t> &destination) = 0;
+			   const libcamera::Span<uint8_t> &destination,
+			   const libcamera::Span<const uint8_t> &exifData) = 0;
 };
 
 #endif /* __ANDROID_JPEG_ENCODER_H__ */

src/android/jpeg/encoder_libjpeg.cpp

@@ -180,7 +180,8 @@ void EncoderLibJpeg::compressNV(const libcamera::MappedBuffer *frame)
 }
 
 int EncoderLibJpeg::encode(const FrameBuffer *source,
-			   const libcamera::Span<uint8_t> &dest)
+			   const libcamera::Span<uint8_t> &dest,
+			   const libcamera::Span<const uint8_t> &exifData)
 {
 	MappedFrameBuffer frame(source, PROT_READ);
 	if (!frame.isValid()) {
@@ -204,6 +205,12 @@ int EncoderLibJpeg::encode(const FrameBuffer *source,
 
 	jpeg_start_compress(&compress_, TRUE);
 
+	if (exifData.size())
+		/* Store Exif data in the JPEG_APP1 data block. */
+		jpeg_write_marker(&compress_, JPEG_APP0 + 1,
+				  static_cast<const JOCTET *>(exifData.data()),
+				  exifData.size());
+
 	LOG(JPEG, Debug) << "JPEG Encode Starting:" << compress_.image_width
 			 << "x" << compress_.image_height;
 

src/android/jpeg/encoder_libjpeg.h

@@ -22,7 +22,8 @@ public:
 
 	int configure(const libcamera::StreamConfiguration &cfg) override;
 	int encode(const libcamera::FrameBuffer *source,
-		   const libcamera::Span<uint8_t> &destination) override;
+		   const libcamera::Span<uint8_t> &destination,
+		   const libcamera::Span<const uint8_t> &exifData) override;
 
 private:
 	void compressRGB(const libcamera::MappedBuffer *frame);

src/android/jpeg/exif.cpp

@@ -168,6 +168,56 @@ void Exif::setString(ExifIfd ifd, ExifTag tag, ExifFormat format, const std::str
 	exif_entry_unref(entry);
 }
 
+void Exif::setMake(const std::string &make)
+{
+	setString(EXIF_IFD_0, EXIF_TAG_MAKE, EXIF_FORMAT_ASCII, make);
+}
+
+void Exif::setModel(const std::string &model)
+{
+	setString(EXIF_IFD_0, EXIF_TAG_MODEL, EXIF_FORMAT_ASCII, model);
+}
+
+void Exif::setSize(const Size &size)
+{
+	setLong(EXIF_IFD_EXIF, EXIF_TAG_PIXEL_Y_DIMENSION, size.height);
+	setLong(EXIF_IFD_EXIF, EXIF_TAG_PIXEL_X_DIMENSION, size.width);
+}
+
+void Exif::setTimestamp(time_t timestamp)
+{
+	char str[20];
+	std::strftime(str, sizeof(str), "%Y:%m:%d %H:%M:%S",
+		      std::localtime(&timestamp));
+	std::string ts(str);
+
+	setString(EXIF_IFD_0, EXIF_TAG_DATE_TIME, EXIF_FORMAT_ASCII, ts);
+	setString(EXIF_IFD_EXIF, EXIF_TAG_DATE_TIME_ORIGINAL, EXIF_FORMAT_ASCII, ts);
+	setString(EXIF_IFD_EXIF, EXIF_TAG_DATE_TIME_DIGITIZED, EXIF_FORMAT_ASCII, ts);
+}
+
+void Exif::setOrientation(int orientation)
+{
+	int value;
+	switch (orientation) {
+	case 0:
+	default:
+		value = 1;
+		break;
+	case 90:
+		value = 8;
+		break;
+	case 180:
+		value = 3;
+		break;
+	case 270:
+		value = 6;
+		break;
+	}
+
+	setShort(EXIF_IFD_0, EXIF_TAG_ORIENTATION, value);
+}
+
 [[nodiscard]] int Exif::generate()
 {
 	if (exifData_) {

src/android/jpeg/exif.h

@@ -12,6 +12,7 @@
 
 #include <libexif/exif-data.h>
 
+#include <libcamera/geometry.h>
 #include <libcamera/span.h>
 
 class Exif
@@ -20,6 +21,13 @@ public:
 	Exif();
 	~Exif();
 
+	void setMake(const std::string &make);
+	void setModel(const std::string &model);
+
+	void setOrientation(int orientation);
+	void setSize(const libcamera::Size &size);
+	void setTimestamp(time_t timestamp);
+
 	libcamera::Span<const uint8_t> data() const { return { exifData_, size_ }; }
 	[[nodiscard]] int generate();