pointArray_svg_arc()

static void pointArray_svg_arc ( stringbuffer_t *  sb, const POINTARRAY *  pa, int  close_ring, int  relative, int  precision  )

static

angles

endAngle - startAngle <= 180 ? "0" : "1"

add MoveTo first point

is circle: need to start at center of circle

add MoveTo center of circle

is circle need to handle differently

Definition at line 162 of file lwout_svg.c.

{
        uint32_t i; //, end;
        char sx[OUT_DOUBLE_BUFFER_SIZE];
        char sy[OUT_DOUBLE_BUFFER_SIZE];
 
        LWDEBUG(2, "pointArray_svg_arc called.");
 
        for (i = 2; i < pa->npoints; i+=2)
        {
                LWDEBUGF(3, "assvg_circstring: arc ending at point %d", i);
                int largeArcFlag, sweepFlag, clockwise;
                int is_circle = LW_FALSE;
                double a1, a3;
                double radius; /* Arc radius */
                double total_angle;
                POINT2D center;
                const POINT2D *t1;
                const POINT2D *t2;
                const POINT2D *t3;
                int p2_side = 0;
                t1 = getPoint2d_cp(pa, i - 2);
                t2 = getPoint2d_cp(pa, i - 1);
                t3 = getPoint2d_cp(pa, i);
                radius = lw_arc_center(t1, t2, t3, &center);
                if ( t1->x == t3->x && t1->y == t3->y ){
                        is_circle = LW_TRUE;
                }
                p2_side = lw_segment_side(t1, t3, t2);
                if ( p2_side == -1 )
                        clockwise = LW_TRUE;
                else
                        clockwise = LW_FALSE;
                /* Angles of each point that defines the arc section */
                a1 = atan2(t1->y - center.y, t1->x - center.x)*180/M_PI;
                //a2 = atan2(t2->y - center.y, t2->x - center.x)*180/M_PI;
                a3 = atan2(t3->y - center.y, t3->x - center.x)*180/M_PI;
 
                LWDEBUGF(2, " center is POINT(%.15g %.15g) - radius:%g", center.x, center.y, radius);
 
                total_angle = clockwise ? a1 - a3 : a3 - a1;
                if (total_angle < 0 ){
                        total_angle += 360;
                }
 
                //stringbuffer_aprintf(sb, "angles (a1 a2 a3): %g %g %g is_circle: %d, total_angle: %g, t1.x: %f, t3.x: %f, t1.y: %f, t3.y: %f ", a1, a2, a3, is_circle, total_angle, t1->x, t3->x, t1->y, t3->y);
 
                largeArcFlag = (total_angle <= 180)? 0 : 1;
                /* The side of the t1/t3 line that t2 falls on dictates the sweep
                direction from t1 to t3. */
                sweepFlag = (p2_side == -1) ? 1 : 0;
                if ( (i == 2) && !is_circle ){
                        lwprint_double(t1->x, precision, sx);
                        lwprint_double(-(t1->y), precision, sy);
                        stringbuffer_aprintf(sb, "%s %s", sx, sy);
                }
                if ( (i == 2) && is_circle){
                        lwprint_double(center.x, precision, sx);
                        lwprint_double(-(center.y), precision, sy);
                        stringbuffer_aprintf(sb, "%s %s", sx, sy);
                }
                lwprint_double(radius, precision, sx);
                lwprint_double(0, precision, sy);
                if (is_circle){
                        //https://stackoverflow.com/questions/5737975/circle-drawing-with-svgs-arc-path
                        lwprint_double(radius*2, precision, sy);
                        stringbuffer_aprintf(sb, " m %s 0 a %s %s 0 1 0 -%s 0", sx, sx, sx, sy);
                        stringbuffer_aprintf(sb, " a %s %s 0 1 0 %s 0", sx, sx, sy);
                }
                else {
                        /* Arc radius radius 0 arcflag swipeflag */
                        if (relative){
                                stringbuffer_aprintf(sb, " a %s %s 0 %d %d ", sx, sx, largeArcFlag, sweepFlag);
                        }
                        else {
                                stringbuffer_aprintf(sb, " A %s %s 0 %d %d ", sx, sx, largeArcFlag, sweepFlag);
                        }
                        lwprint_double(t3->x, precision, sx);
                        lwprint_double(-(t3->y), precision, sy);
                        /* end point */
                        stringbuffer_aprintf(sb, "%s %s", sx, sy);
                }
        }
}

References getPoint2d_cp(), lw_arc_center(), LW_FALSE, lw_segment_side(), LW_TRUE, LWDEBUG, LWDEBUGF, lwprint_double(), POINTARRAY::npoints, OUT_DOUBLE_BUFFER_SIZE, precision, stringbuffer_aprintf(), POINT2D::x, and POINT2D::y.

Referenced by assvg_circstring(), and assvg_compound().

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