[libcamera-devel,v2,2/2] utils: raspberrypi: ctt: dng_load_image: Work with DNG files from Picamera2

16583 diff mbox series

From: William Vinnicombe <william.vinnicombe@raspberrypi.com>

The exif tags are different between raw files from libcamera-apps and
from Picamera2, causing issues loading data.

Add code to identify which tags are being used, and then load the
metadata from the correct tags.

Signed-off-by: William Vinnicombe <william.vinnicombe@raspberrypi.com>
Reviewed-by: David Plowman <david.plowman@raspberrypi.com>
Reviewed-by: Naushir Patuck <naush@raspberrypi.com>
---
 utils/raspberrypi/ctt/ctt_image_load.py | 26 ++++++++++++++++++-------
 1 file changed, 19 insertions(+), 7 deletions(-)

Hi William,

Thank you for the patch.

On Mon, Jul 11, 2022 at 11:26:28AM +0100, william.vinnicombe--- via libcamera-devel wrote:
> From: William Vinnicombe <william.vinnicombe@raspberrypi.com>
> 
> The exif tags are different between raw files from libcamera-apps and
> from Picamera2, causing issues loading data.
> 
> Add code to identify which tags are being used, and then load the
> metadata from the correct tags.

I haven't received a reply to
https://github.com/schoolpost/PiDNG/issues/65 yet so I'm still puzzled
by why PiDNG went this way, but that's not a reason to delay this patch.
I'd like to record more information in the commit message to explain the
issue though. Here's a proposal:

The DNG specification is based on the TIFF file format and recommends
storing the raw image data in a SubIFD and the Exif tags in an Exif IFD.
Other options are allowed, even if not recommended, such as storing both
the raw image data and the Exif data in IFD0, as done by the TIFF/EP
specification.

libcamera-apps use pyexiv2 to produce DNG files, following the DNG
recommendation, while applications based on picamera2 use PiDNG, which
adopts the TIFF/EP structure. Why it does so is not currently clear (see
https://github.com/schoolpost/PiDNG/issues/65 for discussions on this
topic), but as files based on the DNG and TIFF/EP variants exist in the
wild, both need to be supported by ctt.

> Signed-off-by: William Vinnicombe <william.vinnicombe@raspberrypi.com>
> Reviewed-by: David Plowman <david.plowman@raspberrypi.com>
> Reviewed-by: Naushir Patuck <naush@raspberrypi.com>
> ---
>  utils/raspberrypi/ctt/ctt_image_load.py | 26 ++++++++++++++++++-------
>  1 file changed, 19 insertions(+), 7 deletions(-)
> 
> diff --git a/utils/raspberrypi/ctt/ctt_image_load.py b/utils/raspberrypi/ctt/ctt_image_load.py
> index 934db123..29c17581 100644
> --- a/utils/raspberrypi/ctt/ctt_image_load.py
> +++ b/utils/raspberrypi/ctt/ctt_image_load.py
> @@ -301,17 +301,29 @@ def dng_load_image(Cam, im_str):
>          metadata.read()
>  
>          Img.ver = 100  # random value
> -        Img.w = metadata['Exif.SubImage1.ImageWidth'].value
> +        """
> +        libcamera-apps create a separate Exif.Subimage1 for the picture
> +        picamera2 stores everything under Exif.Image
> +        this code detects which one is being used, and therefore extracts the correct values

And here, to match the reworded commit message,

The DNG and TIFF/EP specifications use different IFDs to store the raw
image data and the Exif tags. DNG stores them in a SubIFD and in an Exif
IFD respectively (named "SubImage1" and "Photo" by pyexiv2), while
TIFF/EP stores them both in IFD0 (name "Image"). Both are used in "DNG"
files, with libcamera-apps following the DNG recommendation and
applications based on picamera2 following TIFF/EP.

> +        """
> +        try:
> +            Img.w = metadata['Exif.SubImage1.ImageWidth'].value
> +            subimage = "SubImage1"
> +            photo = "Photo"
> +        except KeyError:
> +            Img.w = metadata['Exif.Image.ImageWidth'].value
> +            subimage = "Image"
> +            photo = "Image"
>          Img.pad = 0
> -        Img.h = metadata['Exif.SubImage1.ImageLength'].value
> -        white = metadata['Exif.SubImage1.WhiteLevel'].value
> +        Img.h = metadata[f'Exif.{subimage}.ImageLength'].value
> +        white = metadata[f'Exif.{subimage}.WhiteLevel'].value
>          Img.sigbits = int(white).bit_length()
>          Img.fmt = (Img.sigbits - 4) // 2
> -        Img.exposure = int(metadata['Exif.Photo.ExposureTime'].value*1000000)
> -        Img.againQ8 = metadata['Exif.Photo.ISOSpeedRatings'].value*256/100
> +        Img.exposure = int(metadata[f'Exif.{photo}.ExposureTime'].value*1000000)
> +        Img.againQ8 = metadata[f'Exif.{photo}.ISOSpeedRatings'].value*256/100
>          Img.againQ8_norm = Img.againQ8 / 256
>          Img.camName = metadata['Exif.Image.Model'].value
> -        Img.blacklevel = int(metadata['Exif.SubImage1.BlackLevel'].value[0])
> +        Img.blacklevel = int(metadata[f'Exif.{subimage}.BlackLevel'].value[0])
>          Img.blacklevel_16 = Img.blacklevel << (16 - Img.sigbits)
>          bayer_case = {
>              '0 1 1 2': (0, (0, 1, 2, 3)),
> @@ -319,7 +331,7 @@ def dng_load_image(Cam, im_str):
>              '2 1 1 0': (2, (3, 2, 1, 0)),
>              '1 0 2 1': (3, (1, 0, 3, 2))
>          }
> -        cfa_pattern = metadata['Exif.SubImage1.CFAPattern'].value
> +        cfa_pattern = metadata[f'Exif.{subimage}.CFAPattern'].value
>          Img.pattern = bayer_case[cfa_pattern][0]
>          Img.order = bayer_case[cfa_pattern][1]
>