Gradient line ?

[jesclaine]

Hi,

Is it possible to have a gradient line in XYlinechart ?

I tried this but is not good :

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XYItemRenderer renderer = plot.getRenderer();
Paint p = new GradientPaint(x1, y1, Color.blue, x2, y2, Color.red);
renderer.setSeriesPaint(0, p);

The problem is i don't know the absolute position of my first point (x1,y1) and of my last point (x2,y2).

Someone have an idea ?

Thanks

[barbarius]

in jfreechart, the lines are drawn one by one. so each line has its own color but jfc doesnt have a mechanism to set that colors seperately.

you can use this method with true parameter at the end for some different look but i dont think this is what you want..

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Paint p = new GradientPaint(x1, y1, Color.blue, x2, y2, Color.red, true);

maybe if you override that method in AbstractRenderer and make a big custom beautiful code, you might return proper gradient paint variables. I dont know if it will work for sure though..:

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public Paint getItemPaint(int row, int column)

[lfkpoa]

My suggestion is for creating a new GradientXYLineAndShapeRenderer like this:

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package org.jfree.chart.demo;

import java.awt.Color;
import java.awt.GradientPaint;
import java.awt.Graphics2D;
import java.awt.Paint;
import java.awt.geom.Rectangle2D;
import org.jfree.chart.plot.PlotRenderingInfo;
import org.jfree.chart.plot.XYPlot;
import org.jfree.chart.renderer.xy.XYItemRendererState;
import org.jfree.chart.renderer.xy.XYLineAndShapeRenderer;
import org.jfree.data.xy.XYDataset;
import org.jfree.util.PaintList;

public class GradientXYLineRenderer extends XYLineAndShapeRenderer {
    private PaintList paintList2;
    private Rectangle2D dataArea;

    public GradientXYLineRenderer() {
        paintList2 = new PaintList();
    }

    public GradientXYLineRenderer(boolean lines, boolean shapes) {
        super(lines, shapes);
        paintList2 = new PaintList();
    }
    
    public void setSeriesPaint2(int series, Paint paint) {
        paintList2.setPaint(series, paint);
    }

    @Override
    public XYItemRendererState initialise(Graphics2D g2, Rectangle2D dataArea, XYPlot plot, XYDataset data, PlotRenderingInfo info) {
        this.dataArea = dataArea;
        return super.initialise(g2, dataArea, plot, data, info);
    }
    
    @Override
    public Paint getSeriesPaint(int series) {
        Paint c1 = super.getSeriesPaint(series);
        if(! (c1 instanceof Color) || dataArea==null)
            return c1;
        Paint c2 = paintList2.getPaint(series);
        if(c2==null || c1==c2 || ! (c2 instanceof Color))
            return c1;
        float y = 1;
        GradientPaint gp = new GradientPaint((float)dataArea.getMinX(),y,(Color) c1,(float)dataArea.getMaxX(),y,(Color)c2);
        return gp;
    }

}

Create a new instance of this renderer, set the Colors you would like to use and set it as the plot renderer:

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     GradientXYLineRenderer renderer = new GradientXYLineRenderer();
     renderer.setSeriesPaint(0, Color.BLUE);
     renderer.setSeriesPaint2(0, Color.WHITE);
     plot.setRenderer(renderer);

[aubreya94]

A line that goes straight across (Horizontal) has a Gradient of zero.
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