Trouble with Imatest Charts

[Guido]

Hi Frans,
I'm have trouble with pictures from an Imatest chart.
Only if I make the picture brighter I get results.
Even with the brighter picture I only get results in the center but not on the top and bottom line.
Any idea what could cause the problem?
Kind regards
Guido

[Frans van den Bergh]

Hi Guido,

Sure! To deal with the image brightness problem you could try adjusting the Threshold parameter (in the GUI, Settings->Preferences, the Threshold field under the "Input Flags" group). Or on the command line, try the -t option, I found -t 0.3 worked with your 139.jpg.

For dealing with Imatest charts there is the --imatest-chart command line option, and the corresponding File->Open Imatest image GUI menu item. Except I noticed that this is not working correctly with your input images. I have not found the root cause yet, but the temporary solution is to crop your images before passing them to MTF Mapper.
For 139.jpg, it seems that cropping about 130 to 150 rows from the top and bottom of the image allows MTF Mapper's --imatest-chart option to work as expected.

Regards,
Frans

[Frans van den Bergh]

Hi Guido,

I have found the underlying reason why MTF Mapper's --imatest-chart option was not working with your images. I think my code was based around an older Imatest chart type that did not have those bright white squares inside the centre column, second row block. Those blocks were brighter than the white background of the chart, causing all kinds of trouble.

I have released MTF Mapper 0.7.40 to fix the problem, your test images should now work correctly (maybe with a little adjustment of the Threshold / -t option to compensate for brightness). I have only released the Windows binaries for the new version; let me know if you require Linux versions. (If you are building from source you should be fine after updating the source and rebuilding).

Regards,
Frans

[Guido]

That worked perfekt.
Thank you very much Frans!
Instead of cropping the picture I put a white rectangle over the two black horizontal lines.

Though I can not save the results on my three windows PC with the save buttons in mtf mapper.
One of them is windows 11 and two are windows 10.
It is not working with mtfmapper 0.7.38 or 0.7.40.

I found the data in:
C:\Users\Guido\AppData\Local\Temp\mtfmappertemp_0

So at least I was able to copy the data from there.

[Guido]

Is it only me having this problem with saving data with the save buttons on windows PCs?