imagetoraster and 16bit images

[jpnp]

When I print a 16bit TIFF file, imagetoraster fails with this in the debug logs:

   DEBUG: TIFF resolution = 70.866142x70.866142, units=3
   DEBUG: Stored resolution = 180x180 PPI
   DEBUG: Bad TIFF dimensions 2104x1488x16x3!
   ERROR: The print file could not be opened.
   ERROR: imagetoraster (PID 259068) stopped with status 1

If I convert the tiff to a 16bit PNG (and use a ppd which specifies /cupsBitsPerColor 16/ then the filter runs and produces a 16bit raster, but it is entirely blank white.

If I force cups to go via imagetopdf by disabling imagetoraster then things are better and gs produces a sensible 16bit raster. The image values are not exactly the same as the input (some sample's channel values are 1-3 out compared to the original image). i.e. it passes an effectively 14-15bit per channel image to gutenprint.

I'm using Ubuntu 20.04 with cups 2.3.1-9ubuntu1.1 and cups-filters 1.27.4-1, and gutenprint 5.3.4.

[tillkamppeter]

Could you attach the 16-bit TIFF file here (or give me a link to a publicly available one)? Thanks.

[jpnp]

Here are a 16bit PNG and 16bit TIFF (zipped as github doesn't like TIFF).
The files can be viewed with the Gnome image viewer, and opened by GIMP or ImageMagick.

1page.zip

[tillkamppeter]

I have checked and the function to read TIFF in libcupsfilters actually does not support 16 bit per color. There was no complaint about that for all the years and so I did not realize that. In addition, direct printing of files to CUPS (not using an application) is only rarely done. Therefore it is also planned to remove support for all image formats except JPG and PNG in cups-filters 2.x.

So I will have a look to see whether it is trivial to fix or whether it will be a wont-fix.

In general you can do high-color-depth printing via PNG and also via PDF (if you print your image from an application, the application will send PDF to CUPS).

[jpnp]

GUI apps offer options and control via print dialogs but are not easily scripted, and it's often hard to have control of colour management. (PhotoPrint works well with gutenprint printers by doing the RIP in app and send raw data to the print queue, but that has been unsupported for years and is unreliable on current OSs.)

PNG is fine as a TIFF alternative. However, when I print the PNG file attached above, I get no errors in the log, but a blank print as output (it gives a totally white cups raster file).

[Harshit09-lang]

@jpnp Could you perhaps upload your /var/log/cups/error_log file after running the problematic job? Set CUPS to debug logging before delivering the task (cupsctil --debug-logging), then modify your error log file to have a .txt extension so that GitHub accepts it.

[tillkamppeter]

@Harshit09-lang you will not need any more from the original poster, I could reproduce it, with both cups-filters 1.x and 2.x. Download this PPD file:
C43x.ppd.txt
and the PNG image from the original poster (click the image). Then run tthe following command line:

cat image.png | PPD=C43x.ppd.txt ./imagetoraster 1 1 1 1 'PageSize=A4 PwgRasterDocumentType=SRgb_16' > out.raster

image.png is the image from the original poster. Open out.raster with rasterview and you see a white page, but at least with correct metadata.

[tillkamppeter]

Fixed in commits c83bead and bb180dc. Thanks, @Harshit09-lang for your contribution!