JFreeChart low performance for MeterPlot

[babak_behzadi]

I'm implementing a web application using spring 4.2.5 and jasperreports 6.4.3.
This app is supposed to generate a pdf file as output. There are three jrxml files:
 
1. firstpage.jrxml: contains logo and some titles

2. intro.jsrxml: contains some texts and a table of items overview

3. items.jrxml: contains some texts and an image to show a JFree MeterPlot output buffer image.

**The code:**

    public void export() {            JasperPrint firstPagePrint = ...;            JasperPrint introPrint = ...;            List<JasperPrint> itemsPrints = new LinkedList<JapserPrint>();            List<Item> items = ...;            for (int i = 0; i < items.size(); i++) {           Item item = items.get(i);           MeterPlot meterPlot = new MeterPlot(new DefaultValueDataset(item.getValue()));           meterPlot.setRange(new Range(item.getMinValue(), item.getMaxValue()));           meterPlot.addInterval(new MeterInterval("bad", new Range(item.getMinValue(), item.getSect1()),                                    Color.red, new BasicStroke(2f), Color.red));           meterPlot.addInterval(new MeterInterval("weak", new Range(item.getSect1(), item.getSect2()),                                    Color.orange, new BasicStroke(2f), Color.orange));           meterPlot.addInterval(new MeterInterval("average", new Range(item.getSect2(), item.getSect3()),                                    Color.yellow, new BasicStroke(2f), Color.yellow));           meterPlot.addInterval(new MeterInterval("good", new Range(item.getSect3(), item.getSect4()),                                    Color.green, new BasicStroke(2f), Color.green));           meterPlot.addInterval(new MeterInterval("excellent", new Range(item.getSect4(), item.getMaxValue()),                                    Color.black, new BasicStroke(2f), Color.BLUE));               JFreeChart jFreeChart = new JFreeChart(item.getTitle(), meterPlot);           BufferedImage bufferedImage = jFreeChart.createBufferedImage(555, 250);           String tmpFile = FileService.JASPER + Util.randomNumeralString(20) + ".png";           ImageIO.write(bufferedImage, "png", new File(tmpFile));           itemAnalysisParams.put("chartImage", tmpFile);           analysisPrints.add(JasperFillManager.fillReport(ITEM_ANALYSIS, itemAnalysisParams, new JREmptyDataSource()));       }       ...export pdf by jasper report prints           }[/code]

**Notice:**

sect1, sect2, sect3 and sect4  are internal limitation for intervals.

    sect = (maxValue - minValue) * 20 / 100    sect1 = this.minValue + sect    sect2 = this.sect1 + sect    sect3 = this.sect2 + sect    sect4 = this.sect3 + sect[/code]

The problem:

The line

BufferedImage bufferedImage = jFreeChart.createBufferedImage(555, 250);[/code]

takes a long time- about 15min- to create image and it repeats for about 45 items and takes 15min*45 total time to generate report.

In advance, I appreciate any help.