[libcamera-devel] [PATCH] qcam: dng_writer: Write EXIF IFD as custom directory

[Niklas Söderlund]

Hi Laurent,

Thanks for your fix, libtiff is fun.

On 2020-05-04 10:04:25 +0300, Laurent Pinchart wrote:
> The EXIF IFD is incorrectly chained to IFD 0 in addition to being a
> referenced as a sub IFD through the EXIFIFD tag. While the libtiff API
> doesn't clearly document why this happens, inspection of the
> TIFFWriteDirectory() source code show that the function treats the IFD
> being written as containing an image, which isn't correct for the EXIF
> IFD. Use TIFFWriteCustomDirectory() instead, which fixes the problem.
> The resulting DNG file can now be opened with darktable in addition to
> rawtherapee.
> 
> Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>

Reviewed-by: Niklas Söderlund <niklas.soderlund at ragnatech.se>

> ---
>  src/qcam/dng_writer.cpp | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/src/qcam/dng_writer.cpp b/src/qcam/dng_writer.cpp
> index ea4616f63d8e..cbd8bed3e6d0 100644
> --- a/src/qcam/dng_writer.cpp
> +++ b/src/qcam/dng_writer.cpp
> @@ -316,9 +316,7 @@ int DNGWriter::write(const char *filename, const Camera *camera,
>  		TIFFSetField(tif, EXIFTAG_EXPOSURETIME, exposureTime);
>  	}
>  
> -	TIFFCheckpointDirectory(tif);
> -	exifIFDOffset = TIFFCurrentDirOffset(tif);
> -	TIFFWriteDirectory(tif);
> +	TIFFWriteCustomDirectory(tif, &exifIFDOffset);
>  
>  	/* Update the IFD offsets and close the file. */
>  	TIFFSetDirectory(tif, 0);
> -- 
> Regards,
> 
> Laurent Pinchart
> 
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-- 
Regards,
Niklas Söderlund