src/main/java/org/jfree/graphics2d/svg/SVGGraphics2D.java
private String getLinearGradientElement(String id, GradientPaint paint) {
        StringBuilder b = new StringBuilder("<linearGradient id=\"").append(id)
                .append("\" ");
        Point2D p1 = paint.getPoint1();
        Point2D p2 = paint.getPoint2();
        b.append("x1=\"").append(geomDP(p1.getX())).append("\" ");
        b.append("y1=\"").append(geomDP(p1.getY())).append("\" ");
        b.append("x2=\"").append(geomDP(p2.getX())).append("\" ");
        b.append("y2=\"").append(geomDP(p2.getY())).append("\" ");
        b.append("gradientUnits=\"userSpaceOnUse\">");
        Color c1 = paint.getColor1();
        b.append("<stop offset=\"0%\" stop-color=\"").append(rgbColorStr(c1))
                .append("\"");
        if (c1.getAlpha() < 255) {
            double alphaPercent = c1.getAlpha() / 255.0;
            b.append(" stop-opacity=\"").append(transformDP(alphaPercent))
                    .append("\"");
        }
        b.append("/>");
        Color c2 = paint.getColor2();
        b.append("<stop offset=\"100%\" stop-color=\"").append(rgbColorStr(c2))
                .append("\"");
        if (c2.getAlpha() < 255) {
            double alphaPercent = c2.getAlpha() / 255.0;
            b.append(" stop-opacity=\"").append(transformDP(alphaPercent))
                    .append("\"");
        }
        b.append("/>");
        return b.append("</linearGradient>").toString();
    }
private String getLinearGradientElement(String id, GradientPaint paint) {
        StringBuilder b = new StringBuilder("<linearGradient id=\"").append(id)
                .append("\" ");
        Point2D p1 = paint.getPoint1();
        Point2D p2 = paint.getPoint2();
        b.append("x1=\"").append(geomDP(p1.getX())).append("\" ");
        b.append("y1=\"").append(geomDP(p1.getY())).append("\" ");
        b.append("x2=\"").append(geomDP(p2.getX())).append("\" ");
        b.append("y2=\"").append(geomDP(p2.getY())).append("\" ");
        b.append("gradientUnits=\"userSpaceOnUse\">");
        Color c1 = paint.getColor1();
        b.append("<stop offset=\"0%\" stop-color=\"").append(rgbColorStr(c1))
                .append("\"");
        if (c1.getAlpha() < 255) {
            double alphaPercent = c1.getAlpha() / 255.0;
            b.append(" stop-opacity=\"").append(transformDP(alphaPercent))
                    .append("\"");
        }
        b.append("/>");
        Color c2 = paint.getColor2();
        b.append("<stop offset=\"100%\" stop-color=\"").append(rgbColorStr(c2))
                .append("\"");
        if (c2.getAlpha() < 255) {
            double alphaPercent = c2.getAlpha() / 255.0;
            b.append(" stop-opacity=\"").append(transformDP(alphaPercent))
                    .append("\"");
        }
        b.append("/>");
        return b.append("</linearGradient>").toString();
    }
Returns an element to represent a linear gradient.  All the linear
gradients that are used get written to the DEFS element in the SVG.

@param id  the reference id.
@param paint  the gradient.

@return The SVG element.