[libcamera-devel] [PATCH 0/3] Initial EXIF metadata support

[Umang Jain]

H Kieran,

On 8/25/20 2:58 AM, Kieran Bingham wrote:
> Hi Umang,
>
> Thanks for taking this on.
>
> On 24/08/2020 21:46, Umang Jain wrote:
>> Hi all,
>>
>> This patch series targets adding initial EXIF metadata support
>> for the frames captured in Android/Libcamera framework.
>>
>> It is initial in the sense, it adds the base infrastructure for
>> Exif metadata support via 'libexif' and also encodes a initial
>> set of metadata tags into the frames.
>>
>> Testing:
>> The testing of this work was carried out via vivid pipeline-handler
>> in conjunction with patch in `cam` using EncoderLibJpeg as the
>> file sink [1]. That way we could see what EXIF metadata could be written
>> and inspect that `exif` or `exiv2` commandline tools.
>>
>> ($) ./build/src/cam/cam -c vivid -C5 -F -s pixelformat=NV12
>>
>> Sample output (1):  exif  frame-stream0-000000.jpg
>> EXIF tags in 'frame-stream0-000000.jpg' ('Intel' byte order):
>> --------------------+----------------------------------------------------------
>> Tag                 |Value
>> --------------------+----------------------------------------------------------
>> Image Width         |1280
>> Image Length        |720
>> Manufacturer        |Libcamera
> Looking at my branch, it was of course me who put this in (incorrectly)
> with a capital L, but please make it lowercase ;-)
>
>> Model               |Camera2111
> I assume you set this Camera2111 string manually for testing ?
>
>
>> Orientation         |Bottom-left
>> X-Resolution        |72
>> Y-Resolution        |72
>> Resolution Unit     |Inch
>> Date and Time       |Sun Oct 13 07:03:20 734137
>>
>> YCbCr Positioning   |Centered
>> Exif Version        |Exif Version 2.1
>> Date and Time (Origi|Sun Oct 13 07:03:20 734137
>>
>> Date and Time (Digit|Sun Oct 13 07:03:20 734137
> Hrm ... we might have some work to do on converting the timestamp values
> appropriately here. That doesn't look right at all ;-)
>
>
>> Components Configura|Y Cb Cr -
>> FlashPixVersion     |FlashPix Version 1.0
>> Color Space         |Internal error (unknown value 65535)
> This one needs to be checked if there is an error/incorrect parameter set.
I found out that, this is not an error. The error messsage however, is 
misleading.
https://github.com/Aries85/LightZone/issues/171#issuecomment-195730879

Color Space 65535 => Uncalibrated.
We are running exif_data_fix(data_); in exif's constructor, so I think 
it's where
this "Uncalibrated" value is getting set as the default value for color 
space.

Can we query colorspace as of now? Then we can try setting it here as well.
>
>> Pixel X Dimension   |1280
>> Pixel Y Dimension   |720
>>
>>
>>
>> Sample output (2): exiv2  frame-stream0-000000.jpg
>> File name       : frame-stream0-000000.jpg
>> File size       : 38787 Bytes
>> MIME type       : image/jpeg
>> Image size      : 1280 x 720
>> Camera make     : Libcamera
>> Camera model    : Camera2111
>> Image timestamp : Sun Oct 13 07:03:20 734137
>>
>> Image number    :
> Hrm, I wonder if we should put the sequence number in here.
>
>
>> Exposure time   :
>> Aperture        :
>> Exposure bias   :
>> Flash           :
>> Flash bias      :
>> Focal length    :
>> Subject distance:
>> ISO speed       :
>> Exposure mode   :
>> Metering mode   :
>> Macro mode      :
>> Image quality   :
> Plenty of parameters we'll want to get from the IPAs there, but that
> will be later.
>
>> Exif Resolution : 1280 x 720
>> White balance   :
>> Thumbnail       : None
>> Copyright       :
>> Exif comment    :
>>
>> There are still a lot of tags that needs to be populated,
>> that can be built on top of this groundwork.
>>
>> [1]: https://github.com/kbingham/libcamera/commit/10ed8ec
>>
>> Kieran Bingham (1):
>>    libcamera: android: Add EXIF infrastructure
>>
>> Umang Jain (2):
>>    android: jpeg: Pass a Exif object while encoding
>>    android: Support initial set of EXIF metadata tags
>>
>>   src/android/camera_device.cpp        |  12 +-
>>   src/android/jpeg/encoder.h           |   5 +-
>>   src/android/jpeg/encoder_libjpeg.cpp |  15 +-
>>   src/android/jpeg/encoder_libjpeg.h   |   3 +-
>>   src/android/jpeg/exif.cpp            | 210 +++++++++++++++++++++++++++
>>   src/android/jpeg/exif.h              |  53 +++++++
>>   src/android/meson.build              |   2 +
>>   7 files changed, 296 insertions(+), 4 deletions(-)
>>   create mode 100644 src/android/jpeg/exif.cpp
>>   create mode 100644 src/android/jpeg/exif.h
>>