[PATCH] apps: common: dng_writer: Workaround for "Unknown tag 33421" error

[Kieran Bingham]

Quoting Stefan Klug (2024-06-25 09:01:11)
> In libtiff version 4.5.1 and later the CFA* tags were missing. This got
> fixed in https://gitlab.com/libtiff/libtiff/-/commit/49856998c3d82e65444b47bb4fb11b7830a0c2be
> Unfortunately the fix is not released yet, but the faulty libtiff is
> contained in current buildroot. As a local fix is pretty easy and
> without side effects, let's workaround that.
> 
> Signed-off-by: Stefan Klug <stefan.klug at ideasonboard.com>
> ---
>  src/apps/common/dng_writer.cpp | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/src/apps/common/dng_writer.cpp b/src/apps/common/dng_writer.cpp
> index 103e5c828c4d..7375577e920f 100644
> --- a/src/apps/common/dng_writer.cpp
> +++ b/src/apps/common/dng_writer.cpp
> @@ -541,6 +541,23 @@ int DNGWriter::write(const char *filename, const Camera *camera,
>  
>         TIFFWriteDirectory(tif);
>  
> +       /*
> +        * Workaround for a bug introduced in libtiff version 4.5.1 and no fix
> +        * released. In these versions the CFA* tags were missing in the field
> +        * info.
> +        * Introduced by: https://gitlab.com/libtiff/libtiff/-/commit/738e04099b13192bb1f654e74e9b5829313f3161
> +        * Fixed by: https://gitlab.com/libtiff/libtiff/-/commit/49856998c3d82e65444b47bb4fb11b7830a0c2be
> +        */
> +       if (!TIFFFindField(tif, TIFFTAG_CFAREPEATPATTERNDIM, TIFF_ANY)) {
> +               static const TIFFFieldInfo infos[] = {
> +                       { TIFFTAG_EP_CFAREPEATPATTERNDIM, 2, 2, TIFF_SHORT, FIELD_CUSTOM,
> +                         1, 0, const_cast<char *>("EP CFARepeatPatternDim") },
> +                       { TIFFTAG_EP_CFAPATTERN, -1, -1, TIFF_BYTE, FIELD_CUSTOM,
> +                         1, 1, const_cast<char *>("EP CFAPattern") },
> +               };

As a workaround it sounds fine, but shouldn't there be something here
which writes out the pattern based on the metadata/properties of the
camera/raw stream? Or are these always fixed data entries?

Aha, actually I think I see this is preparing the fields so that it can
be set below!


Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>

> +               TIFFMergeFieldInfo(tif, infos, 2);
> +       }
> +
>         /* Create a new IFD for the RAW image. */
>         const uint16_t cfaRepeatPatternDim[] = { 2, 2 };
>         const uint8_t cfaPlaneColor[] = {
> -- 
> 2.43.0
>