[xcrysden] Determine the angstrom to pixel ratio for printed images

[Matic Poberznik]

Dear Libin,

> Can I fix the angstrom/pixel value before printing? Alternatively, can I know the angstrom/pixel value after the printing (I do not want to do the calibration myself since there are many structure files)? 

> Another solution to this problem is to understand how XCrysDen determines the angstrom/pixel at the beginning of opening a structure. Unfortunately, the src code is too complex for me to find out the answer. 
> 
> Actually, it is enough to determine the relative values of angstrom/pixel for different structure files. 

XCrysDen doesn't determine the angstrom/pixel ration instead it
determines the display bounding box from the input structure (for
example it uses the crystal cell parameters to determine the display
size for crystals). So if you're cell remains the same the size of atoms
should as well.

A way to ensure the same orientation and zoom (for structures with the
same cell parameters) is by using "Save current state and structure"
option, i.e.

File => Save Current State and Structure

This will create a file *.xcrysden suffix. You can "load" an alternative
xsf file into this script and the zoom and orientation will remain the
same.

You do this by opening the *.xcrysden file with a text editor and
editing the "STRUCTURE-PART" of the file. (i.e. delete all structure
data and replace the line:

::scripting::open --xsf $system(SCRDIR)/xc_xsf.$system(PID)

with

::scripting::open --xsf /path/to/xsf/name.xsf

where name.xsf is your xsf file (if it's in the current working
directory the path isn't needed)
You open the script file with the command:

xcrysden -s nameofscript.xcrysden

Further information for scripting files is available here:

http://www.xcrysden.org/doc/scripting.html

Also when posting to the mailing list please state your name and
affiliation.

Best Regards,

Matic Poberznik
J. Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia