private String makeRelativeCubicBezierCurve(final SvgPoint controlPoint1, final SvgPoint controlPoint2, final SvgPoint endPoint) {
        final String sControlPoint1 = controlPoint1.toRelativeCoordinates(mLastPoint);
        final String sControlPoint2 = controlPoint2.toRelativeCoordinates(mLastPoint);
        final String sEndPoint = endPoint.toRelativeCoordinates(mLastPoint);

        final StringBuilder sb = new StringBuilder();
        sb.append(sControlPoint1);
        sb.append(" ");
        sb.append(sControlPoint2);
        sb.append(" ");
        sb.append(sEndPoint);
        sb.append(" ");

        // discard zero curve
        final String svg = sb.toString();
        if ("c0 0 0 0 0 0".equals(svg)) {
            return "";
        } else {
            return svg;
        }
    }
Build a SVG path as a string.

https://www.w3.org/TR/SVGTiny12/paths.html
signature-pad/src/main/java/com/github/gcacace/signaturepad/utils/SvgPathBuilder.java