yes Mark, I know that the axis is reversed, but I don't get the point
why the if clause is needed: fabs(pt->y) always returns a positive value
or 0 and multiplying 0 with -1 doesn't do any harm. So why not use
sprintf(y, "%.*f", precision, pt->y * -1) and skip the test?
Klaus
Mark Cave-Ayland wrote:
Klaus Förster wrote:
I've just checked the source of lwgeom_svg.c in postgis-1.3.4rc3 and
wonder what the fabs() testing in lines 243, 262, 303, 324 and 348 is
for. Why is it needed?
e.g. line 243:
sprintf(y, "%.*f", precision, fabs(pt->y) > 0 ? (pt->y * -1) : pt->y);
thanks for any hints,
Klaus
Hi Klaus,
The trick is the use of the ? operator, and so the above logic reads:
if fabs(pt->y) > 0 then value = (pt->y * -1), otherwise value = pt->y
In other words, it inverts the Y-axis - presumably because SVG has a
top-left origin point as opposed to a bottom-left origin point used by
the majority of coordinate systems.
HTH,
Mark.
--
Klaus Förster
Institut für Geographie
Universität Innsbruck
A-6020 Innsbruck, Innrain 52
Tel.: +43 (0)512 507 5434
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