在Jfreechart中更改图形的X轴起始值 [英] To change the X-axis starting value of graph in Jfreechart

问题描述

我正在计算图像红色成分的直方图，并将其存储在redhisto []中。数组的索引表示强度（0到255）
，值表示具有该强度的像素数。然后用JFreeChart绘制这些值。

I am calculating histogram of red component of the image and stored it in redhisto[]. The index of the array represent the intensity(0 to 255) and the value represent the number of pixel with that intensity. Then plotting those values with JFreeChart.

我的问题是：

1. 如何使X轴值从0开始。现在它从负数开始。



2. 我们可以更改图形中条形的颜色
   
   代码为：

1. How to make X-axis value start from 0. Now its starting from negative number.

2. Can we change the color of the bars in the graph code is :

 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);
 }
}

推荐答案

您可以更改域轴的下限并设置系列绘制，如下所示。默认的 XYBarPainter 有一个渐变颜色突出显示，所以我使用了 StandardXYBarPainter 。

You can change the lower bound of the domain axis and set the series paint as shown below. The default XYBarPainter has a gradient color highlight, so I used a 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);

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