imexpr question

svensk wrote on Jul 08, 2010

IRAF newbie here.

I am trying to use imexpr to do some pixel replacements.

My function:

cl> imexpr "(a > 70000) ? 10*b : a" c

simply replaces an overexposed pixel from "a" with a properly exposed and scaled pixel from "b". This works as expected on a single image set, assuming they are named "a" and "b" but I'd like imexpr to do this to a list of files.

So I thought:

cl> imexpr "(a > 70000) ? 10*b : a" @final
operand a: @long
operand b: @short

but I get an error after the operand a prompt that says

ERROR: Cannot open image (@long)

Can operands not be lists? How should I be rethinking this? Any help is greatly appreciated.

Thanks!

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Mike Fitzpatrick wrote on Jul 08, 2010

Right, operands must be single images or values. To work on lists you'll need to write a small script to process the list with repeated calls to imexpr, e.g.

cl> list = "myfile.txt"
cl> while (fscan (list, s1) != EOF) {
>>      imexpr ( ....., a=s1, .... )
>> }

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svensk wrote on Jul 08, 2010

fitz

Right, operands must be single images or values. To work on lists you'll need to write a small script to process the list with repeated calls to imexpr, e.g.

cl> list = "myfile.txt"
cl> while (fscan (list, s1) != EOF) {
>>      imexpr ( ....., a=s1, .... )
>> }

How should my long and short exposure list be delimited in the txt file?

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Mike Fitzpatrick wrote on Jul 08, 2010

How should my long and short exposure list be delimited in the txt file?

As separate files? Like I said, IMEXPR does one image at a time, it doesn't know what you think is a 'long' vs a 'short' exposure so it all depends on how you write the loops.

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Last post on Jul 08, 2010