library/src/main/java/com/github/siyamed/shapeimageview/path/parser/PathParser.java
private static void drawArc(Path path, double x0, double y0, double x, double y, double rx,
                                double ry, double angle, boolean largeArcFlag, boolean sweepFlag) {
        double dx2 = (x0 - x) / 2.0;
        double dy2 = (y0 - y) / 2.0;
        angle = Math.toRadians(angle % 360.0);
        double cosAngle = Math.cos(angle);
        double sinAngle = Math.sin(angle);

        double x1 = (cosAngle * dx2 + sinAngle * dy2);
        double y1 = (-sinAngle * dx2 + cosAngle * dy2);
        rx = Math.abs(rx);
        ry = Math.abs(ry);

        double Prx = rx * rx;
        double Pry = ry * ry;
        double Px1 = x1 * x1;
        double Py1 = y1 * y1;

        // check that radii are large enough
        double radiiCheck = Px1 / Prx + Py1 / Pry;
        if (radiiCheck > 1) {
            rx = Math.sqrt(radiiCheck) * rx;
            ry = Math.sqrt(radiiCheck) * ry;
            Prx = rx * rx;
            Pry = ry * ry;
        }

        // Step 2 : Compute (cx1, cy1)
        double sign = (largeArcFlag == sweepFlag) ? -1 : 1;
        double sq = ((Prx * Pry) - (Prx * Py1) - (Pry * Px1))
                / ((Prx * Py1) + (Pry * Px1));
        sq = (sq < 0) ? 0 : sq;
        double coef = (sign * Math.sqrt(sq));
        double cx1 = coef * ((rx * y1) / ry);
        double cy1 = coef * -((ry * x1) / rx);

        double sx2 = (x0 + x) / 2.0;
        double sy2 = (y0 + y) / 2.0;
        double cx = sx2 + (cosAngle * cx1 - sinAngle * cy1);
        double cy = sy2 + (sinAngle * cx1 + cosAngle * cy1);

        // Step 4 : Compute the angleStart (angle1) and the angleExtent (dangle)
        double ux = (x1 - cx1) / rx;
        double uy = (y1 - cy1) / ry;
        double vx = (-x1 - cx1) / rx;
        double vy = (-y1 - cy1) / ry;
        double p, n;

        // Compute the angle start
        n = Math.sqrt((ux * ux) + (uy * uy));
        p = ux; // (1 * ux) + (0 * uy)
        sign = (uy < 0) ? -1.0 : 1.0;
        double angleStart = Math.toDegrees(sign * Math.acos(p / n));

        // Compute the angle extent
        n = Math.sqrt((ux * ux + uy * uy) * (vx * vx + vy * vy));
        p = ux * vx + uy * vy;
        sign = (ux * vy - uy * vx < 0) ? -1.0 : 1.0;
        double angleExtent = Math.toDegrees(sign * Math.acos(p / n));
        if (!sweepFlag && angleExtent > 0) {
            angleExtent -= 360f;
        } else if (sweepFlag && angleExtent < 0) {
            angleExtent += 360f;
        }
        angleExtent %= 360f;
        angleStart %= 360f;

        RectF oval = new RectF((float) (cx - rx), (float) (cy - ry), (float) (cx + rx), (float) (cy + ry));
        path.addArc(oval, (float) angleStart, (float) angleExtent);
    }
private static void drawArc(Path path, double x0, double y0, double x, double y, double rx,
                                double ry, double angle, boolean largeArcFlag, boolean sweepFlag) {
        double dx2 = (x0 - x) / 2.0;
        double dy2 = (y0 - y) / 2.0;
        angle = Math.toRadians(angle % 360.0);
        double cosAngle = Math.cos(angle);
        double sinAngle = Math.sin(angle);

        double x1 = (cosAngle * dx2 + sinAngle * dy2);
        double y1 = (-sinAngle * dx2 + cosAngle * dy2);
        rx = Math.abs(rx);
        ry = Math.abs(ry);

        double Prx = rx * rx;
        double Pry = ry * ry;
        double Px1 = x1 * x1;
        double Py1 = y1 * y1;

        // check that radii are large enough
        double radiiCheck = Px1 / Prx + Py1 / Pry;
        if (radiiCheck > 1) {
            rx = Math.sqrt(radiiCheck) * rx;
            ry = Math.sqrt(radiiCheck) * ry;
            Prx = rx * rx;
            Pry = ry * ry;
        }

        // Step 2 : Compute (cx1, cy1)
        double sign = (largeArcFlag == sweepFlag) ? -1 : 1;
        double sq = ((Prx * Pry) - (Prx * Py1) - (Pry * Px1))
                / ((Prx * Py1) + (Pry * Px1));
        sq = (sq < 0) ? 0 : sq;
        double coef = (sign * Math.sqrt(sq));
        double cx1 = coef * ((rx * y1) / ry);
        double cy1 = coef * -((ry * x1) / rx);

        double sx2 = (x0 + x) / 2.0;
        double sy2 = (y0 + y) / 2.0;
        double cx = sx2 + (cosAngle * cx1 - sinAngle * cy1);
        double cy = sy2 + (sinAngle * cx1 + cosAngle * cy1);

        // Step 4 : Compute the angleStart (angle1) and the angleExtent (dangle)
        double ux = (x1 - cx1) / rx;
        double uy = (y1 - cy1) / ry;
        double vx = (-x1 - cx1) / rx;
        double vy = (-y1 - cy1) / ry;
        double p, n;

        // Compute the angle start
        n = Math.sqrt((ux * ux) + (uy * uy));
        p = ux; // (1 * ux) + (0 * uy)
        sign = (uy < 0) ? -1.0 : 1.0;
        double angleStart = Math.toDegrees(sign * Math.acos(p / n));

        // Compute the angle extent
        n = Math.sqrt((ux * ux + uy * uy) * (vx * vx + vy * vy));
        p = ux * vx + uy * vy;
        sign = (ux * vy - uy * vx < 0) ? -1.0 : 1.0;
        double angleExtent = Math.toDegrees(sign * Math.acos(p / n));
        if (!sweepFlag && angleExtent > 0) {
            angleExtent -= 360f;
        } else if (sweepFlag && angleExtent < 0) {
            angleExtent += 360f;
        }
        angleExtent %= 360f;
        angleStart %= 360f;

        RectF oval = new RectF((float) (cx - rx), (float) (cy - ry), (float) (cx + rx), (float) (cy + ry));
        path.addArc(oval, (float) angleStart, (float) angleExtent);
    }
/*
Elliptical arc implementation based on the SVG specification notes
Adapted from the Batik library (Apache-2 license) by SAU