Exporting Images

jCharts exports to the following formats: PNG, JPEG, and SVG, via encoder objects located in the org.krysalis.jcharts.encoders package. Each of these encoders has a method to encode your charts:

encode( Chart chart, OutputStream outputStream ) - a generic version so you can pass any implementation of OutputStream through this method, such as FileOutputStream.

PNG and JPEG support is provided through the JSDK 1.4. In other words, you need the JSDK 1.4 to use the provided jCharts image encoders. However, there is now a JPEGEncoder13 class for legacy support of older JDK's.

SVG support is provided via the Apache XML project: Batik. Please visit: http://xml.apache.org/batik/

There has been a helper Class, org.krysalis.jcharts.encoders.ServletEncoderHelper, added for exporting charts from Servlets and JSP's. There are methods on this class to export to any of the jCharts supported formats, with the added benefit of automatically setting the MIME type of the chart for your browser so that the browser knows how to render the image correctly.

I don't know about you, but I always had trouble remembering the MIME types for different file formats.

The JSDK 1.4+ allows jCharts to run on a headless *nix box without a virtual frame buffer! Set the follow property may be specified at the java command line: -Djava.awt.headless=true or a less flexible placement in your code: System.setProperty("java.awt.headless","true");

Otherwise, if you are running pre JDK 1.4, you will have to use a virtual frame buffer, like: xvfb.

You can also use jcharts inside a Swing application. Below is the SwingDemo Class from the org.krysalis.jcharts.demo.swing package. Here, you simply set the Graphics Object from your Swing Component, into the Chart and call: render()

import org.krysalis.jcharts.chartData.ChartDataException;
import org.krysalis.jcharts.chartData.PieChartDataSet;
import org.krysalis.jcharts.properties.PropertyException;
import org.krysalis.jcharts.properties.PieChart2DProperties;
import org.krysalis.jcharts.properties.ChartProperties;
import org.krysalis.jcharts.properties.LegendProperties;
import org.krysalis.jcharts.nonAxisChart.PieChart2D;

import javax.swing.*;
import java.awt.*;
import java.awt.event.WindowEvent;


public class SwingDemo extends JFrame
{
  private JPanel panel;


  public SwingDemo() throws ChartDataException, PropertyException
  {
    initComponents();
  }


  private void initComponents() throws ChartDataException,PropertyException
  {
    this.setSize( 500, 500 );
    this.panel = new JPanel( true );
    this.panel.setSize( 500, 500 );
    this.getContentPane().add( this.panel );

    this.pieChart2DProperties = new PieChart2DProperties();
    this.legendProperties= new LegendProperties();
    this.chartProperties= new ChartProperties();

    this.setVisible( true );


    addWindowListener( new java.awt.event.WindowAdapter()
    {
      public void windowClosing( WindowEvent windowEvent )
      {
        exitForm( windowEvent );
      }
    }
    );
  }


  /************************************************************************
	*
	* @param graphics
	***********************************************************************/
  public void paint( Graphics graphics )
  {
    try {
      String[] labels = {"BMW", "Audi", "Lexus"};
      String title = "Cars that Own";
      Paint[] paints = {Color.blue, Color.gray, Color.red};
      double[] data = {50d, 30d, 20d};
      PieChartDataSet pieChartDataSet = new PieChartDataSet( title, data,
                               labels, paints, this.pieChart2DProperties );
      Dimension dimension= this.panel.getSize();
      PieChart2D pieChart2D = new PieChart2D( pieChartDataSet,
                                              this.legendProperties,
                                              this.chartProperties,
                                              (int) dimension.getWidth(),
                                              (int) dimension.getHeight() );

       //***** BEGIN SWING SPECIFIC CODE *******************************
       pieChart2D.setGraphics2D( (Graphics2D) this.panel.getGraphics() );
       pieChart2D.render();
       //***** END SWING SPECIFIC CODE *********************************
    }
    catch( ChartDataException chartDataException ) {
      chartDataException.printStackTrace();
    }
    catch( PropertyException propertyException ) {
      propertyException.printStackTrace();
    }
  }


  private void exitForm( WindowEvent windowEvent )
  {
    System.exit( 0 );
  }


  public static void main( String args[] ) throws ChartDataException,
                                                        PropertyException
  {
    new SwingDemo();
  }
}