Legacy ImageMagick Discussions Archive

I want to convert compressed tiff(Group4 - CCITT_T.6) to PNG format image.

Link to compressed tiff: https://drive.google.com/file/d/1lsNRRR ... sp=sharing

Below command does NOT work becuase tif image is compressed(Group4 CCITT_T.6):
convert.exe CCITT_T.6_Compressed.TIF -auto-orient -strip test.png

I tried so far with:
ImageMagick-6.9.10-34-portable-Q16-x64 (convert.exe)
ImageMagick-7.0.7-11-portable-Q16-x64 (convert.exe / magick.exe)

I keep getting below errors:
Bad value 0 for "ResolutionUnit" tag. `_TIFFVSetField' @ error/tiff.c/TIFFErrors/608. OR
Bad value 0 for "ResolutionUnit" tag. `_TIFFVSetField' @ error/tiff.c/TIFFErrors/645.

The "ResolutionUnit" error prevents IM from reading and processing the file.

As a workaround, the program tiffcp reports the error but allows processing, writing a result without the problem, that can then be processed by IM.

I have already reported this privately to the ImageMagick developers. It works in older versions of ImageMagick such as 6.9.3.0, but not in current versions of IM 6 or 7. Libtiff will handle it, but ImageMagick is seeing that message as an error and perhaps it should just be a warning.

ImageMagick is behaving properly. The exception is thrown by the libtiff delegate library and we respond accordingly. Any TIFF image, upon opening, that throws an error exception is cause for ImageMagick to exit. You can query the libtiff developers to determine if the exception is mis-classified. If libtiff instead throws a warning, ImageMagick can safely ignore the warning and continue execution.

In older versions this does work with the same libtiff and an image is created. So what has changed?

You may recall the developers have spent this last year hardening ImageMagick to make it more secure. ImageMagick previously was forgiving about errors, now its not.

OK. Thanks.