[libcamera-devel] [PATCH v5 1/2] libcamera: android: Add EXIF infrastructure

[Laurent Pinchart]

Hi Umang,

Thank you for the patch.

On Thu, Sep 03, 2020 at 10:02:15PM +0530, Umang Jain wrote:
> From: Kieran Bingham <kieran.bingham at ideasonboard.com>
> 
> 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 at ideasonboard.com>
> Signed-off-by: Umang Jain <email at uajain.com>
> Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
> ---
>  src/android/jpeg/exif.cpp | 189 ++++++++++++++++++++++++++++++++++++++
>  src/android/jpeg/exif.h   |  46 ++++++++++
>  src/android/meson.build   |   2 +
>  3 files changed, 237 insertions(+)
>  create mode 100644 src/android/jpeg/exif.cpp
>  create mode 100644 src/android/jpeg/exif.h
> 
> diff --git a/src/android/jpeg/exif.cpp b/src/android/jpeg/exif.cpp
> new file mode 100644
> index 0000000..9d8d9bc
> --- /dev/null
> +++ b/src/android/jpeg/exif.cpp
> @@ -0,0 +1,189 @@
> +/* 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;
> +	}
> +
> +	entry->tag = tag;

exif_entry_initialize() sets entry->tag, so I think you can skip this.

> +
> +	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)

I think unsigned int is enough for components, we will never need more
than 4G components :-)

> +{
> +	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);
> +}
> +
> +int Exif::generate()
> +{
> +	if (exifData_) {
> +		free(exifData_);
> +		exifData_ = nullptr;
> +	}
> +
> +	if (!valid_) {
> +		LOG(EXIF, Error) << "Created EXIF instance is invalid";
> +		return -1;
> +	}
> +
> +	exif_data_save_data(data_, &exifData_, &size_);
> +
> +	LOG(EXIF, Debug) << "Created EXIF instance (" << size_ << " bytes)";

I'd write "Generated EXIF data", as the instance is this class.

> +
> +	return 0;
> +}
> diff --git a/src/android/jpeg/exif.h b/src/android/jpeg/exif.h
> new file mode 100644
> index 0000000..8fb8ffd
> --- /dev/null
> +++ b/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_ }; }
> +	int [[nodiscard]]  generate();

The attribute goes at the beginning of the line (clang generated an
error otherwise). The attribute should also be specified in the .cpp
file.

Please make sure to (compile-)test patches before sending them :-)

With those small issues fixed,

Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>

> +
> +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__ */
> diff --git a/src/android/meson.build b/src/android/meson.build
> index f7b81a4..ecb92f6 100644
> --- a/src/android/meson.build
> +++ b/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'),
>  ]
>  

-- 
Regards,

Laurent Pinchart