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

[Laurent Pinchart]

Hi Stefan,

Thank you for the patch.

On Tue, Jun 25, 2024 at 10:01:11AM +0200, Stefan Klug wrote:
> 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") },

This will fail to compile with libtiff versions older than v4.5.1, where
the bug was introduced. TIFFTAG_CFAREPEATPATTERNDIM and
TIFFTAG_CFAPATTERN became aliases for TIFFTAG_EP_CFAREPEATPATTERNDIM and
TIFFTAG_EP_CFAPATTERN in that version, so I think you can switch to
TIFFTAG_CFAREPEATPATTERNDIM and TIFFTAG_CFAPATTERN here. I would also
change the description string to drop the "EP " prefix.

With that,

Reviewed-by: Laurent Pinchart <laurent.pinchart 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[] = {

-- 
Regards,

Laurent Pinchart