在 Jfreechart 中更改图形的 X 轴起始值答案

【问题标题】：To change the X-axis starting value of graph in Jfreechart在 Jfreechart 中更改图形的 X 轴起始值
【发布时间】：2014-01-12 09:00:40
【问题描述】：

我正在计算图像红色分量的直方图并将其存储在 redhisto[] 中。数组的索引代表强度（0到255）该值表示具有该强度的像素数。然后用 JFreeChart 绘制这些值。

我的问题是：

如何使 X 轴值从 0 开始。现在它从负数开始。

我们可以更改图表中条形的颜色吗代码是：

 public class Histogram extends ApplicationFrame {
   public Histogram(final String title) throws IOException {
    super(title);
    IntervalXYDataset dataset = createDataset();
    JFreeChart chart = createChart(dataset);
    final ChartPanel chartPanel = new ChartPanel(chart);
    chartPanel.setPreferredSize(new java.awt.Dimension(500, 270));
    setContentPane(chartPanel);
   }

  private IntervalXYDataset createDataset() throws IOException {
   BufferedImage imageA = ImageIO.read(new File("XYZ.bmp"));
   int[] red = new int[imageA.getHeight()*imageA.getWidth()];
   int[] redhisto = new int[256];
   int[] pixel;
   int k= 0;
   for (int y = 0; y < imageA.getHeight(); y++) {
      for (int x = 0; x < imageA.getWidth(); x++) {
        pixel = imageA.getRaster().getPixel(x, y, new int[3]);       
        red[k] = pixel[0];
        k++;
      }
   }        

   for(int x=0;x<red.length;x++){
       int y = red[x];
       redhisto[y]++;
    }

  final XYSeries series = new XYSeries("No of pixels");
  for(int i=0; i<redhisto.length;i++)
    series.add(i,redhisto[i]);

  final XYSeriesCollection dataset = new XYSeriesCollection(series);
  return dataset;
 }

 private JFreeChart createChart(IntervalXYDataset dataset) {
  final JFreeChart chart = ChartFactory.createXYBarChart("Color Intensity   Histogram","X",false,"Y",dataset,PlotOrientation.VERTICAL,true,true,false);
  XYPlot plot = (XYPlot) chart.getPlot();
  return chart;    
 }

 public static void main(final String[] args) throws IOException {
  final Histogram demo = new Histogram("Image Histogram");
  demo.pack();
  RefineryUtilities.centerFrameOnScreen(demo);
  demo.setVisible(true);
 }
}

【问题讨论】：

标签： java jfreechart

【解决方案1】：

您可以更改域轴的下限并设置系列绘制，如下所示。默认XYBarPainter有渐变色高亮，所以我用了StandardXYBarPainter。

XYPlot plot = (XYPlot) chart.getPlot();
ValueAxis axis = plot.getDomainAxis();
axis.setLowerBound(0);
XYBarRenderer r = (XYBarRenderer) plot.getRenderer();
r.setBarPainter(new StandardXYBarPainter());
r.setSeriesPaint(0, Color.blue);

【讨论】：

【解决方案2】：

    XYPlot plot = (XYPlot) chart.getPlot();  

    //To change the lower bound of X-axis
    NumberAxis xAxis = (NumberAxis) plot.getDomainAxis();
    xAxis.setLowerBound(0);

    //To change the lower bound of Y-axis       
    NumberAxis yAxis = (NumberAxis) plot.getRangeAxis();
    yAxis.setLowerBound(0);

    // To change the color
    XYItemRenderer renderer = plot.getRenderer();
    renderer.setSeriesPaint(0, Color.green);

【讨论】：