mathfns.h revision f10eb2c8e53724d2e6055b539da14e65aaa843c3
/*
* Inkscape::Util::... some mathmatical functions
*
* Authors:
* Johan Engelen <goejendaagh@zonnet.nl>
*
* Copyright (C) 2007 Johan Engelen
*
* Released under GNU GPL, read the file 'COPYING' for more information
*/
#ifndef SEEN_INKSCAPE_UTIL_MATHFNS_H
#define SEEN_INKSCAPE_UTIL_MATHFNS_H
namespace Inkscape {
namespace Util {
/**
* Returns area in triangle given by points; may be negative.
*/
inline double
triangle_area (NR::Point p1, NR::Point p2, NR::Point p3)
{
return (p1[NR::X]*p2[NR::Y] + p1[NR::Y]*p3[NR::X] + p2[NR::X]*p3[NR::Y] - p2[NR::Y]*p3[NR::X] - p1[NR::Y]*p2[NR::X] - p1[NR::X]*p3[NR::Y]);
}
/**
* \return x rounded to the nearest multiple of c1 plus c0.
*
* \note
* If c1==0 (and c0 is finite), then returns +/-inf. This makes grid spacing of zero
* mean "ignore the grid in this dimension".
*/
inline double round_to_nearest_multiple_plus(double x, double const c1, double const c0)
{
return floor((x - c0) / c1 + .5) * c1 + c0;
}
/**
* \return x rounded to the lower multiple of c1 plus c0.
*
* \note
* If c1==0 (and c0 is finite), then returns +/-inf. This makes grid spacing of zero
* mean "ignore the grid in this dimension".
*/
inline double round_to_lower_multiple_plus(double x, double const c1, double const c0)
{
return floor((x - c0) / c1) * c1 + c0;
}
/**
* \return x rounded to the upper multiple of c1 plus c0.
*
* \note
* If c1==0 (and c0 is finite), then returns +/-inf. This makes grid spacing of zero
* mean "ignore the grid in this dimension".
*/
inline double round_to_upper_multiple_plus(double x, double const c1, double const c0)
{
return ceil((x - c0) / c1) * c1 + c0;
}
}
}
#endif
/*
Local Variables:
mode:c++
c-file-style:"stroustrup"
c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
indent-tabs-mode:nil
fill-column:99
End:
*/
// vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:encoding=utf-8:textwidth=99 :