android: jpeg: Add EXIF infrastructure

Provide helper classes to utilise the libexif interfaces and link
against libexif to support tag additions when creating JPEG images.

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/jpeg/exif.cpp

@@ -0,0 +1,188 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Copyright (C) 2020, Google Inc.
+ *
+ * exif.cpp - EXIF tag creation using libexif
+ */
+
+#include "exif.h"
+
+#include "libcamera/internal/log.h"
+
+using namespace libcamera;
+
+LOG_DEFINE_CATEGORY(EXIF)
+
+/*
+ * The Exif class should be instantiated and specific properties set
+ * through the exposed public API.
+ *
+ * Once all desired properties have been set, the user shall call
+ * generate() to process the entries and generate the Exif data.
+ *
+ * Calls to generate() must check the return code to determine if any error
+ * occurred during the construction of the Exif data, and if successful the
+ * data can be obtained using the data() method.
+ */
+Exif::Exif()
+	: valid_(false), data_(nullptr), exifData_(0), size_(0)
+{
+	/* Create an ExifMem allocator to construct entries. */
+	mem_ = exif_mem_new_default();
+	if (!mem_) {
+		LOG(EXIF, Error) << "Failed to allocate ExifMem Allocator";
+		return;
+	}
+
+	data_ = exif_data_new_mem(mem_);
+	if (!data_) {
+		LOG(EXIF, Error) << "Failed to allocate an ExifData structure";
+		return;
+	}
+
+	valid_ = true;
+
+	exif_data_set_option(data_, EXIF_DATA_OPTION_FOLLOW_SPECIFICATION);
+	exif_data_set_data_type(data_, EXIF_DATA_TYPE_COMPRESSED);
+
+	/*
+	 * Big-Endian: EXIF_BYTE_ORDER_MOTOROLA
+	 * Little Endian: EXIF_BYTE_ORDER_INTEL
+	 */
+	exif_data_set_byte_order(data_, EXIF_BYTE_ORDER_INTEL);
+
+	/* Create the mandatory EXIF fields with default data. */
+	exif_data_fix(data_);
+}
+
+Exif::~Exif()
+{
+	if (exifData_)
+		free(exifData_);
+
+	if (data_)
+		exif_data_unref(data_);
+
+	if (mem_)
+		exif_mem_unref(mem_);
+}
+
+ExifEntry *Exif::createEntry(ExifIfd ifd, ExifTag tag)
+{
+	ExifContent *content = data_->ifd[ifd];
+	ExifEntry *entry = exif_content_get_entry(content, tag);
+
+	if (entry) {
+		exif_entry_ref(entry);
+		return entry;
+	}
+
+	entry = exif_entry_new_mem(mem_);
+	if (!entry) {
+		LOG(EXIF, Error) << "Failed to allocated new entry";
+		valid_ = false;
+		return nullptr;
+	}
+
+	exif_content_add_entry(content, entry);
+	exif_entry_initialize(entry, tag);
+
+	return entry;
+}
+
+ExifEntry *Exif::createEntry(ExifIfd ifd, ExifTag tag, ExifFormat format,
+			     unsigned long components, unsigned int size)
+{
+	ExifContent *content = data_->ifd[ifd];
+
+	/* Replace any existing entry with the same tag. */
+	ExifEntry *existing = exif_content_get_entry(content, tag);
+	exif_content_remove_entry(content, existing);
+
+	ExifEntry *entry = exif_entry_new_mem(mem_);
+	if (!entry) {
+		LOG(EXIF, Error) << "Failed to allocated new entry";
+		valid_ = false;
+		return nullptr;
+	}
+
+	void *buffer = exif_mem_alloc(mem_, size);
+	if (!buffer) {
+		LOG(EXIF, Error) << "Failed to allocate buffer for variable entry";
+		exif_mem_unref(mem_);
+		valid_ = false;
+		return nullptr;
+	}
+
+	entry->data = static_cast<unsigned char *>(buffer);
+	entry->components = components;
+	entry->format = format;
+	entry->size = size;
+	entry->tag = tag;
+
+	exif_content_add_entry(content, entry);
+
+	return entry;
+}
+
+void Exif::setShort(ExifIfd ifd, ExifTag tag, uint16_t item)
+{
+	ExifEntry *entry = createEntry(ifd, tag);
+	if (!entry)
+		return;
+
+	exif_set_short(entry->data, EXIF_BYTE_ORDER_INTEL, item);
+	exif_entry_unref(entry);
+}
+
+void Exif::setLong(ExifIfd ifd, ExifTag tag, uint32_t item)
+{
+	ExifEntry *entry = createEntry(ifd, tag);
+	if (!entry)
+		return;
+
+	exif_set_long(entry->data, EXIF_BYTE_ORDER_INTEL, item);
+	exif_entry_unref(entry);
+}
+
+void Exif::setRational(ExifIfd ifd, ExifTag tag, ExifRational item)
+{
+	ExifEntry *entry = createEntry(ifd, tag);
+	if (!entry)
+		return;
+
+	exif_set_rational(entry->data, EXIF_BYTE_ORDER_INTEL, item);
+	exif_entry_unref(entry);
+}
+
+void Exif::setString(ExifIfd ifd, ExifTag tag, ExifFormat format, const std::string &item)
+{
+	/* Pad 1 extra byte for null-terminated string. */
+	size_t length = item.length() + 1;
+
+	ExifEntry *entry = createEntry(ifd, tag, format, length, length);
+	if (!entry)
+		return;
+
+	memcpy(entry->data, item.c_str(), length);
+	exif_entry_unref(entry);
+}
+
+[[nodiscard]] int Exif::generate()
+{
+	if (exifData_) {
+		free(exifData_);
+		exifData_ = nullptr;
+	}
+
+	if (!valid_) {
+		LOG(EXIF, Error) << "Generated EXIF data is invalid";
+		return -1;
+	}
+
+	exif_data_save_data(data_, &exifData_, &size_);
+
+	LOG(EXIF, Debug) << "Created EXIF instance (" << size_ << " bytes)";
+
+	return 0;
+}

src/android/jpeg/exif.h

@@ -0,0 +1,46 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Copyright (C) 2020, Google Inc.
+ *
+ * exif.h - EXIF tag creator using libexif
+ */
+#ifndef __ANDROID_JPEG_EXIF_H__
+#define __ANDROID_JPEG_EXIF_H__
+
+#include <ctime>
+#include <string>
+
+#include <libexif/exif-data.h>
+
+#include <libcamera/span.h>
+
+class Exif
+{
+public:
+	Exif();
+	~Exif();
+
+	libcamera::Span<const uint8_t> data() const { return { exifData_, size_ }; }
+	[[nodiscard]] int generate();
+
+private:
+	ExifEntry *createEntry(ExifIfd ifd, ExifTag tag);
+	ExifEntry *createEntry(ExifIfd ifd, ExifTag tag, ExifFormat format,
+			       unsigned long components, unsigned int size);
+
+	void setShort(ExifIfd ifd, ExifTag tag, uint16_t item);
+	void setLong(ExifIfd ifd, ExifTag tag, uint32_t item);
+	void setString(ExifIfd ifd, ExifTag tag, ExifFormat format,
+		       const std::string &item);
+	void setRational(ExifIfd ifd, ExifTag tag, ExifRational item);
+
+	bool valid_;
+
+	ExifData *data_;
+	ExifMem *mem_;
+
+	unsigned char *exifData_;
+	unsigned int size_;
+};
+
+#endif /* __ANDROID_JPEG_EXIF_H__ */

src/android/meson.build

@@ -7,6 +7,7 @@ android_hal_sources = files([
     'camera_metadata.cpp',
     'camera_ops.cpp',
     'jpeg/encoder_libjpeg.cpp',
+    'jpeg/exif.cpp',
 ])
 
 android_camera_metadata_sources = files([
@@ -14,6 +15,7 @@ android_camera_metadata_sources = files([
 ])
 
 android_deps = [
+    dependency('libexif'),
     dependency('libjpeg'),
 ]