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Differences Between QPOE Files and Image Arrays

QPOE files are event lists. They store information relevant to the arrival of each photon such as position, energy, arrival time, etc. Image arrays are arrays of numbers representing total counts at each position - even if that count may be zero. IMAGE ARRAYS contain SPATIAL INFORMATION only and do NOT contain information such as arrival time or energy. Confusion as to filtering, and input and output formats (qp vs. imh) for various tasks can be alleviated keeping these facts in mind.

• hedit

  The task hedit allows the editing of the header parameter in a image file, but does not work on QPOE files. It looks as though it works properly but it does not. The PROS task qphedit updates QPOE headers.

• Storing of images in the data directory

  IRAF image data is stored by default in the image directory imdir, i.e., *.pix files are written in imdir while *.imh files are written in the current directory, and indicate where the data is stored. No such structure exists with QPOE files, i.e. *.qp files are stored in the current directory. Make sure there is space in your directory before trying to create a QPOE file (for example from xpr2qp).

• Filtering on QPOE files

  On the command line, filters of the PROS type on QPOE files must be specified within quotes. e.g.

   im> imcopy "xdata$rp110590.qp[pi=2:10]" foo.imh        # the input file
                                                              # is rp90.imh
  

  
  but in interactive mode no quotes are needed

  
  

    im> imcopy
    Input images: xdata$rp110590.qp[pi=2:10]                 # No quotes
  

  However, standard IRAF region selections do not require quotes. e.g.

    im> imcopy xdata$rp110590.qp[100:200,100:200] foo.imh
  

  
  

  If in doubt, include quotes. e.g.

    im> imcopy "xdata$rp110590.qp[100:200,100:200]" foo.imh
  

  will work correctly.

  Filters may be combined within brackets, e.g.

    im> qplist "xdata$rp110590.qp[pi=10:20,x=2000:3000,y=2000:3000]"
  

  When blocking and filtering is done simultaneously, the blocking factor is placed in its own pair of brackets, separate from the filter (see Imcopy??).

• Filtering of the QPOE kind

  Filtering commands such as `block=' only work with PROS software on QPOE files. Unfortunately, however, they are accepted by regular IRAF tasks, i.e., no error message or warning will result, so that one might assume they worked properly. e.g.

  
  

    im> imcopy ``rp90[block=2]" foo
  

  
  produces a file foo.imh of the same size as rp90.imh.