IMEXPR: odd behavior with single character image names

Frank Valdes wrote on Aug 25, 1998

Q:  Any idea why this doesn't work? I have been using imexpr successfully...

imexpr "(a == -10) ? -10 : b" output=vgs.imh a=v.imh b=vgstemp.imh
ERROR: bad image parameter reference vgstemp.imh


A:  This is a quirk of this task.  The variable names in the expression are
a-z.  The values of these variables can be images or image header
parameters.  For image header parameters the syntax is operand.param.
So in your case:

imexpr "(a == -10) ? -10 : b" output=vgs.imh a=v.imh b=vgstemp.imh
ERROR: bad image parameter reference vgstemp.imh

where you have a=v.imh, I believe the task is saying use the header
parameter "imh" from operand image "v".  The error message is also
wrong.  So your workaround is to either rename your image to be other
than a single lower-case letter or not use the full image name with
the extension.  For the latter solution use:

imexpr "(a == -10) ? -10 : b" output=vgs.imh a=v b=vgstemp.imh

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Last post on Aug 25, 1998