In plotting data or displaying images in a LUX window on your screen, you can select from various coordinate systems. These coordinate systems are listed below.
DEPThe magnitude-dependent coordinate system. It corresponds to the
dev system if the coordinate is negative or if the magnitude of
the coordinate is greater than or equal to 1, and to the dvi
system if the magnitude is less than 1.
DVIThe device-independent coordinate system. The origin is in the lower
left-hand corner of the screen, and the coordinates increase toward the
upper right-hand corner, which has coordinates (1,1).
DEVThe device-dependent coordinate system. The origin, with coordinates
(0,0), is in the lower left-hand corner of the screen, and the
coordinates increase toward the upper right-hand corner. The unit is
one pixel.
PLTThe plot coordinate system. The coordinates increase from left to right
and from bottom to top. The origin and scale correspond to that of the
last-drawn plot window (i.e., plt point (!mxb,!myb)
corresponds to dvi point (!wxb,!wyb), and plt point
(!mxt,!myt) to dvi point (!wxt,!wyt)).
RPLThe relative plot-coordinate system. The origin is in the lower
left-hand corner of the last drawn plot window, at dvi point
(!wxb,!wyb), and the coordinates increase to (1,1) in the
upper right-hand corner of the last drawn plot, at dvi point
(!wxt,!wyt)).
IMGThe image coordinate system. By default, the origin is at the lower
left-hand corner of the last displayed image (at dev coordinates
(!tvix,!tviy), and the coordinates increase toward the upper
right-hand corner. However, if SET,/YREVERSEIMG has been
executed, then image coordinates are measured using the native
X11 coordinate orientation, with the image origin in the upper
left-hand corner and the coordinates increasing toward the lower
right-hand corner. The unit is equal to !tvscale pixels.
RIMThe relative image-coordinate system. By default, the origin is at the
lower left-hand corner of the last displayed image (at dev
coordinates (!tvix,!tviy), and the coordinates increase toward
the upper right-hand corner, whose coordinates are (1,1).
However, if SET,/YREVERSEIMG has been executed, then image
coordinates are measured using the native X11 coordinate
orientation, with the image origin in the upper left-hand corner and the
coordinates increasing toward the lower right-hand corner.
X11The native X11 coordinate system, with its origin at the upper
left-hand corner of the window, the y coordinate increasing downward,
and with a unit of one pixel.
Several graphics routines allow you to specify coordinates as well as
the coordinate system in which these coordinates are expressed. You
specify a particular coordinate system by including a keyword
corresponding to one of the coordinate system codes listed above, e.g.,
/PLT for the plt coordinate system. Alternatively, you
can specify the coordinate system numerically through the mode
keyword MODE=#coordsys.sys where sys stands for the
three-letter abbreviation of the coordinate system name.
For example, you can display a box (symbol type -4) at
coordinates (100,200) in the img coordinate system through
command XYMOV,100,200,-4,/IMG, or
XYMOV,100,200,-4,MODE=#coordsys.IMG. The latter form is more
convenient if you want to allow the user to select a coordinate system
through a parameter of a user-defined subroutine or function.
In older versions of LUX, image positions in routines such as tv
were specified in a coordinate system that had its origin in the upper
left-hand corner with the y coordinate increasing towards the bottom,
and the position specified for an image was the location of its upper
left-hand corner (the X11 coordinate system). TV,x,0,0
would display an image in the upper left-hand corner of the window. In
the current version of LUX, image positions are specified in the
dev coordinate system, and the specified position is the one of
the lower left-hand corner of the image, so TV,x,0,0 displays an
image in the lower left-hand corner of the window. For backwards
compatibility, one can still request the older-style image coordinate
specification (i.e., the X11 coordinate system) as default, by
executing SET,/ULIMCOORDS, and the older-style image orientation
(with the image origin in the upper left-hand corner of the image) by
executing SET,/YREVERSEIMG.
See also: !mxb, !mxt, !myb, !myt, set, !tvix, !tviy, !tvscale, !wxb, !wxt, !wyb, !wyt, #coordsys