Most functions in Display are accessible either from the clickable, keyboard pop-up menu or the typing the corresponding key on the actual keyboard. The key will be indicated in square brackets (e.g. [Key]) in this documentation.
From a terminal/console window:
$> Display directory/path/if/required/mri_file.mnc path/if/req/pet_file1.mnc path/if/req/pet_file2.mnc ...
Also, I recommend closing any unnecessary windows and minimizing all other applications so that the 4-panel window can be viewed with no other layers above or below it. When using the "Save Slice Image" option, it seems that everything in the panel (including bits from other windows) of interest gets saved.
If the system can't find the file you've indicated, or if there is a problem with the file, you should get an error message in the terminal window:
$> Display data/doc/bad_file_name.mnc Inputting data/doc/bad_file_name.mnc. Error: opening MINC file "data/doc/bad_file_name.mnc". Error loading data/doc/bad_file_name.mnc
$> Display data/doc/bad_file_type.mnc Inputting data/doc/bad_file_type.mnc. Error: opening MINC file "data/doc/bad_file_type.mnc". Error loading data/doc/bad_file_type.mnc
To change the settings of
From the Main menu, select "Slice View" [S], then Current Volume [T] and keep pressing [T] until the image you want becomes active. When it is, the colour bar (left hand side) and the title bar (top) of the 4-panel window will display the appropriate colour scheme and filename.
Pop to Main menu [space], Select Colour Coding [D], Select desired colour scheme:
In the Colour Coding Menu, select Overcolour [X] and type "transparent" at the prompt in the terminal window. Then, select Undercolour [Z] and type "transparent" at the prompt in the terminal window.
Although tab-completion does not work in the Display terminal window, you can use the mouse to highlight (select with left mouse button) and paste (click middle mouse button) text in the terminal window.
Use sliders on colour bar or, from the Colour Coding Menu, select Range [H] and type in the lower and upper limits at the prompt in the terminal window.
Pop to the Main menu [space], choose Segmenting [F], Cursor Vis On/Off [4]
Pop to the Main menu [space], select File [T]. Put the mouse arrow over the slice of interest and type from the keyboard [S]. Type in a meaningful file name at the prompt in the terminal window. The file is saved in .rgb format; it will be useful if you use that extension as part of the filename.
Use imgview or imgworks, from another terminal window.
$> imgworks meaningful_filename.rgb
The program imgworks allows you to crop the image and perform other manipulations. If you double-click the image file from the "Finder" it will open with imgview.
Both imgview and imgworks allow you to save in various popular file formats (.gif, .tiff, etc.). Imgview seems to have more file format options.