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CrystFEL detector geometry files
--------------------------------

The detector geometry is taken from a text file rather than hardcoded into the
program.  Programs which care about the geometry (indexamajig, pattern_sim and
powder_plot) take an argument "--geometry=<file>" (or "-g <file>"), where <file>
contains the geometry.  CrystFEL's representation of a detector is broken down
into one or more "panels", each of which has its own location for the centre of
the panel (i.e. the location of the central beam), its own camera length,
resolution and so on.  Each panel fits into the overall image taken from the
HDF5 file, defined by minimum and maximum coordinates in x and y.  The
coordinates are specified inclusively, meaning that a minimum of 0 and a maximum
of 9 results in ten items.  Counting begins from zero.  All pixels in the image
must be assigned to a panel.

See "A note on data orientation" in the top level README file for important
information about how CrystFEL defines the axes.  All coordinates (including the
centre coordinates for each panel) are measured according to these axes:  there
is no coordinate system local to a panel.

The syntax for a simple geometry might be as follows:

; The number of panels
n_panels = 1

; "0/" specifies the first (and only) panel.  If we had more panels, there would
; be a copy of the following lines but prefixes with "1/", "2/" and so on.

; The region of the image which belongs to this panel:
0/min_x = 0
0/max_x = 1023
0/min_y = 512
0/max_y = 1023

; The coordinates of the central beam which should be
; used for pixels in this panel:
0/cx = 491.9
0/cy = 440.7

; The camera length (in metres) for this panel
0/clen = 67.8e-3

; The resolution (in pixels per metre) for this panel
0/res = 13333.3  ; 75 micron pixel size

; The readout direction (x or y).  If more than three peaks are found in
; the same readout region, they are all discarded.  This helps to avoid
; problems due to streaks appearing along the readout direction.
0/badrow_direction = y


See the "examples" folder for some examples.