iraf.net

NUMBER:	502
MODULE:	pl files and fixpix, imreplace, and others
SYSTEM:	V2.12
DATE:	Mon Jul 22 08:42:45 MST 2002
FROM:	valdes

BUG:	Between IRAF versions 2.11 and 2.12 there was a change in the
	structure of pixel list (pl) files to allow for larger images.  The
	change was made so that old format pl files can be read.  However,
	updating of old format files is not supported.  This means some
	tasks that truly work in-place, such as IMREPLACE, will fail.
	(Tasks that replace the input file by their result using a
	temporary intermediate file, which are more common, are not truly
	in-place operations and so do not have this problem.)  It is a bug
	that in-place update operations will result in the file being
	deleted.  Some tasks don't actually write out a pl file but
	internally modify it.  The task FIXPIX is in this class.  This will
	result in the same type of error.  Typically the error is 'Cannot
	update image header'.  The workaround is to use IMCOPY to create a
	new version of the pl files when starting with V2.11 or early files
	but working with V2.12.

STATUS:	There is currently no plan to support pl update operations on
	the older pl format.