java – 显示图像数据的直方图

我有时需要显示 image data in the form of a histogram的表示.我对访问图像数据的方式特别感兴趣.我熟悉JFreeChart,其中包括直方图支持,但我会考虑其他方法.

解决方法

> Raster方法getSamples()从BufferedImage中提取每个色带的值.
> HistogramDataset方法addSeries()将每个波段的计数添加到数据集.
> A StandardXYBarPainter替换ChartFactory默认值,如here所示.
>定制DefaultDrawingSupplier提供每个系列所需的颜色;它包含半透明的颜色.
> here的变形here用于控制每个频带的可见度;使用ChartMouseListener的补充方法如here所示.

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.EventQueue;
import java.awt.Paint;
import java.awt.event.ActionEvent;
import java.awt.image.BufferedImage;
import java.awt.image.Raster;
import java.io.IOException;
import java.net.URL;
import javax.imageio.ImageIO;
import javax.swing.AbstractAction;
import javax.swing.ImageIcon;
import javax.swing.JCheckBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import org.jfree.chart.ChartFactory;
import org.jfree.chart.ChartPanel;
import org.jfree.chart.JFreeChart;
import org.jfree.chart.plot.DefaultDrawingSupplier;
import org.jfree.chart.plot.PlotOrientation;
import org.jfree.chart.plot.XYPlot;
import org.jfree.chart.renderer.xy.StandardXYBarPainter;
import org.jfree.chart.renderer.xy.XYBarRenderer;
import org.jfree.data.statistics.HistogramDataset;

/**
 * @see https://stackoverflow.com/q/40537278/230513
 * @see https://stackoverflow.com/q/11870416/230513
 * @see https://stackoverflow.com/a/28519356/230513
 */
public class Histogram {

    private static final int BINS = 256;
    private final BufferedImage image = getImage();
    private HistogramDataset dataset;
    private XYBarRenderer renderer;

    private BufferedImage getImage() {
        try {
            return ImageIO.read(new URL(
                "http://i.imgur.com/kxXhIH1.jpg"));
        } catch (IOException e) {
            e.printStackTrace(System.err);
        }
        return null;
    }

    private ChartPanel createChartPanel() {
        // dataset
        dataset = new HistogramDataset();
        Raster raster = image.getRaster();
        final int w = image.getWidth();
        final int h = image.getHeight();
        double[] r = new double[w * h];
        r = raster.getSamples(0,w,h,r);
        dataset.addSeries("Red",r,BINS);
        r = raster.getSamples(0,1,r);
        dataset.addSeries("Green",2,r);
        dataset.addSeries("Blue",BINS);
        // chart
        JFreeChart chart = ChartFactory.createHistogram("Histogram","Value","Count",dataset,PlotOrientation.VERTICAL,true,false);
        XYPlot plot = (XYPlot) chart.getPlot();
        renderer = (XYBarRenderer) plot.getRenderer();
        renderer.setBarPainter(new StandardXYBarPainter());
        // translucent red,green & blue
        Paint[] paintArray = {
            new Color(0x80ff0000,true),new Color(0x8000ff00,new Color(0x800000ff,true)
        };
        plot.setDrawingSupplier(new DefaultDrawingSupplier(
            paintArray,DefaultDrawingSupplier.DEFAULT_FILL_PAINT_SEQUENCE,DefaultDrawingSupplier.DEFAULT_OUTLINE_PAINT_SEQUENCE,DefaultDrawingSupplier.DEFAULT_STROKE_SEQUENCE,DefaultDrawingSupplier.DEFAULT_OUTLINE_STROKE_SEQUENCE,DefaultDrawingSupplier.DEFAULT_SHAPE_SEQUENCE));
        ChartPanel panel = new ChartPanel(chart);
        panel.setMouseWheelEnabled(true);
        return panel;
    }

    private JPanel createControlPanel() {
        JPanel panel = new JPanel();
        panel.add(new JCheckBox(new VisibleAction(0)));
        panel.add(new JCheckBox(new VisibleAction(1)));
        panel.add(new JCheckBox(new VisibleAction(2)));
        return panel;
    }

    private class VisibleAction extends AbstractAction {

        private final int i;

        public VisibleAction(int i) {
            this.i = i;
            this.putValue(NAME,(String) dataset.getSeriesKey(i));
            this.putValue(SELECTED_KEY,true);
            renderer.setSeriesVisible(i,true);
        }

        @Override
        public void actionPerformed(ActionEvent e) {
            renderer.setSeriesVisible(i,!renderer.getSeriesVisible(i));
        }
    }

    private void display() {
        JFrame f = new JFrame("Histogram");
        f.setDefaultCloSEOperation(JFrame.EXIT_ON_CLOSE);
        f.add(createChartPanel());
        f.add(createControlPanel(),BorderLayout.SOUTH);
        f.add(new JLabel(new ImageIcon(image)),BorderLayout.WEST);
        f.pack();
        f.setLocationRelativeTo(null);
        f.setVisible(true);
    }

    public static void main(String[] args) {
        EventQueue.invokeLater(() -> {
            new Histogram().display();
        });
    }
}

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