(texdraw)Resolution

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5.2.2 Resolution
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TeXdraw scales coordinates before passing them to PostScript.  Keeping
track of the coordinate scaling is necessary, in any event, to allow
TeXdraw to compute the maximum excursions of the coordinates.  TeXdraw
uses pixel units in its PostScript code.  One pixel unit is equal to
1/300 of an inch.  TeXdraw issues PostScript commands with integer
valued pixel coordinates.  This sets the positioning resolution for
TeXdraw.  The passing of integer valued coordinates which correspond to
the device resolution keeps lines aligned with the device grid; parallel
lines of the same width will be rendered with the same width.

   The position saving mechanism in TeXdraw (Note: Saving positions)
associates the pixel coordinates of a position with the specified name.

   TeXdraw uses the limited real number representation provided by TeX.
These operations are based on the representation of dimensions as
real-valued numbers of points.  Internally in TeX, dimensions are stored
32-bit values, normalized so that 1 pt corresponds to the scaled point
(sp) value of 65536.  Dimensions with magnitudes between 0.000015 pt and
32767 pt can be represented.  This is also the dynamic range of the
TeXdraw pixel coordinates passed to PostScript.  TeXdraw must convert
from user supplied coordinates using the scaling factor (which itself
consists of two components, the unit scale and the segment scale) and a
pixel conversion factor.  The use of limited precision real numbers in
these computations can cause accumulation of error when relative scaling
is used repeatedly.