[libcamera-devel] [PATCH 2/4] android: jpeg: exif: Simplify setGPSDateTimestamp and setGPSDMS

[Laurent Pinchart]

Hi Paul,

Thank you for the patch.

On Mon, Mar 08, 2021 at 10:46:42AM +0000, Kieran Bingham wrote:
> On 08/03/2021 10:13, Paul Elder wrote:
> > Now that setRational() supports setting multiple rational values, use
> > that in setGPSDateTimestamp and setGPSDMS which previously set every
> > rational manually.
> 
> This feels better to me ;-)
> 
> > Signed-off-by: Paul Elder <paul.elder at ideasonboard.com>
> > ---
> >  src/android/jpeg/exif.cpp | 24 ++----------------------
> >  1 file changed, 2 insertions(+), 22 deletions(-)
> > 
> > diff --git a/src/android/jpeg/exif.cpp b/src/android/jpeg/exif.cpp
> > index e5a3e448..c8b2f072 100644
> > --- a/src/android/jpeg/exif.cpp
> > +++ b/src/android/jpeg/exif.cpp
> > @@ -345,24 +345,13 @@ void Exif::setGPSDateTimestamp(time_t timestamp)
> >  		  EXIF_FORMAT_ASCII, tsStr);
> >  
> >  	/* Set GPS_TIME_STAMP */
> > -	ExifEntry *entry =
> > -		createEntry(EXIF_IFD_GPS,
> > -			    static_cast<ExifTag>(EXIF_TAG_GPS_TIME_STAMP),
> > -			    EXIF_FORMAT_RATIONAL, 3, 3 * sizeof(ExifRational));
> > -	if (!entry)
> > -		return;
> > -
> >  	ExifRational ts[] = {
> >  		{ static_cast<ExifLong>(tm.tm_hour), 1 },
> >  		{ static_cast<ExifLong>(tm.tm_min),  1 },
> >  		{ static_cast<ExifLong>(tm.tm_sec),  1 },
> >  	};
> >  
> > -	for (int i = 0; i < 3; i++)
> > -		exif_set_rational(entry->data + i * sizeof(ExifRational),
> > -				  order_, ts[i]);
> > -
> > -	exif_entry_unref(entry);
> > +	setRational(EXIF_IFD_GPS, static_cast<ExifTag>(EXIF_TAG_GPS_TIME_STAMP), 3, ts);
> 
> We're now encoding the size of these tags (EXIF_TAG_GPS_TIME_STAMP) in
> our layer, where for most other tags are defined by libexif.
> 
> Given that libexif doesn't support those tags correctly it would seem,
> this is fine - but perhaps we should send a patch to libexif as well.

I've been tempted to send patches to libexif before...

> Even if we patch libexif, we will still have to do this ourselves so no
> blocker.

... and this is what stopped me :-) Coupled with the fact that the
libexif API definitely shows its age, and I would have been too tempted
of rewriting parts of it :-D The project doesn't seem very active, but
it could still be worth a try.

> Also rather than hardcoding '3' should we use std::size(coords) ?

I assume you mean ts here. If setRational() switched to Span, then this
would be automatic :-)

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

> 5cfbbcd20731 ("libcamera: Replace ARRAY_SIZE() with std::size()")
> suggests it should be possible.
> 
> >  }
> >  
> >  std::tuple<int, int, int> Exif::degreesToDMS(double decimalDegrees)
> > @@ -376,22 +365,13 @@ std::tuple<int, int, int> Exif::degreesToDMS(double decimalDegrees)
> >  
> >  void Exif::setGPSDMS(ExifIfd ifd, ExifTag tag, int deg, int min, int sec)
> >  {
> > -	ExifEntry *entry = createEntry(ifd, tag, EXIF_FORMAT_RATIONAL, 3,
> > -				       3 * sizeof(ExifRational));
> > -	if (!entry)
> > -		return;
> > -
> >  	ExifRational coords[] = {
> >  		{ static_cast<ExifLong>(deg), 1 },
> >  		{ static_cast<ExifLong>(min), 1 },
> >  		{ static_cast<ExifLong>(sec), 1 },
> >  	};
> >  
> > -	for (int i = 0; i < 3; i++)
> > -		exif_set_rational(entry->data + i * sizeof(ExifRational),
> > -				  order_, coords[i]);
> > -
> > -	exif_entry_unref(entry);
> > +	setRational(ifd, tag, 3, coords);
> 
> And here with std::size()
> 
> With that
> 
> Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
> 
> >  }
> >  
> >  /*

-- 
Regards,

Laurent Pinchart