PJSR: some questions (creating dir, writing FITS key)

[kwiechen]

Hello,

I have two questions regarding PJSR programming:

1) Is there an OS-independent way to check if a directory exists and to create one if not?

2) Is it possible to write FITS keywords and values back when saving an ImageWindow?

Best,

Kai

[Juan Conejero]

Hi Kai,

1) Is there an OS-independent way to check if a directory exists and to create one if not?

These global methods of the File object provide the functionality you're looking for:

Boolean File.directoryExists( String dirPath )
void File.createDirectory( String dirPath[, Boolean createIntermediateDirs=true] )

Example:

var pathToMyDir = "/path/to/mydir";
if ( !File.directoryExists( pathToMyDir ) )
   File.createDirectory( pathToMyDir );

2) Is it possible to write FITS keywords and values back when saving an ImageWindow?

The ImageWindow.keywords property is an array of FITSKeyword objects:

Array ImageWindow.keywords

The FITSKeyword object has name, value and comment String properties that you can read and write. It also has a constructor that allows you to set all of these properties at once:

new FITSKeyword( String name, String value[, String comment] )

Using the keywords property you can get and set FITS keywords for an image window before saving it. For example:

ImageWindow window = ImageWindow.activeWindow;
if ( !window.isNull )
   window.keywords.push( new FITSKeyword( "MYKWD", 123.456, "my private keyword" ) );

Hope this helps.

[kwiechen]

Thank you! Is a PJSR documentation available?

Best,

Kai

[georg.viehoever]

Thank you! Is a PJSR documentation available?

Not really. Your best bet is the bubble help that appear when you hover above function calls in the script editor browser window, and trying to derive the functionality from the PCL documentation http://pixinsight.com/developer/pcl/doc/index.html . Some of the Core Javascript Objects are also documented in Javascript tutorials (e.g. Array).

Of course, you can always ask in the forum, and Juan will usually help within in couple of days.
Georg

[zvrastil]

Just to make sure it is not forgot, I'd like to cite Juan's word from this recent post: http://pixinsight.com/forum/index.php?topic=3585.msg24965#msg24965 .

Then we'll have to start documenting the PJSR, which is another important pending task, but that's a different story.

cheers, Zbynek

[kwiechen]

/*
The ImageWindow.keywords property is an array of FITSKeyword objects:

Array ImageWindow.keywords

The FITSKeyword object has name, value and comment String properties that you can read and write. It also has a constructor that allows you to set all of these properties at once:

new FITSKeyword( String name, String value[, String comment] )

Using the keywords property you can get and set FITS keywords for an image window before saving it. For example:

ImageWindow window = ImageWindow.activeWindow;
if ( !window.isNull )
   window.keywords.push( new FITSKeyword( "MYKWD", 123.456, "my private keyword" ) );

*/

I have tried for example this:

var img = ImageWindow.windowById(id);
var kw = new FITSKeyword( "MyKW", "MyValue");
img.keywords.push( kw  ) ;
img.saveAs(savePath, false, false, false, false);
img.forceClose();

The FITSKeyword object is correctly constructed. The resulting FITS file does not contain the FITSKeyword and trying to query img.keywords.length gives 0

What is going wrong here?

Best,

Kai

[Juan Conejero]

Hi Kai,

The problem is here:

img.keywords.push( kw  ) ;

The ImageWindow.keywords property yields a *new* Array object that is a copy of the current list of FITS keywords in the image window. It does not give a reference to the current list. Hence, the above code is functionally equivalent to:

var a = img.keywords;
a.push( kw );

Note that this is a feature of the JavaScript language, not of the PJSR: properties are in general not mutable. The correct way to do what you want is this:

var a = img.keywords;
a.push( kw );
img.keywords = a;

Hope this helps.

[kwiechen]

Thank you very much - this does work! Sorry for these questions and problems - its my first try with javascript.

Best

Kai

[Juan Conejero]

Kai, thank *you* for your interest in PI and in scripting on PI, and sorry for not having a complete documentation for PJSR. Hopefully we'll be able to fix this lack in a near future.

Please keep all the questions coming; I'll always be happy to answer everything related to PJSR and PCL development.