使用Chart2D的直方图 [英] Histogram using Chart2D

问题描述

我想绘制JPEG的系数直方图。我在Google上搜索了几个小时，知道如何使用 Chart2D 库，但是没有教程提供示例。我想要绘制的数组是 hist [] 。我创建了一个 LBChart2D 的对象，但我不知道如何将数组设置为数据集。

I want to draw coefficient histogram of JPEG. I'm searching on Google for hours to know how to use Chart2D library, but there is no tutorial with examples. The array which I want to draw is hist[]. I created an object of LBChart2D, but I don't know how to set the array as data set to it.

//coeff[] is the coefficients array
for(int i=0;i<coeff.length;i++)
hist[coeff[i]]++;

LBChart2D lbChart2D = new LBChart2D();

编辑：这是我正在尝试的：

Here is what I'm trying :

Object2DProperties object2DProps = new Object2DProperties();
object2DProps.setObjectTitleText ("Title ");
Chart2DProperties chart2DProps = new Chart2DProperties();
chart2DProps.setChartBetweenChartAndLegendGapThicknessModel(5);
LegendProperties legendProps = new LegendProperties();
legendProps .setLegendBorderThicknessModel(5);
legendProps.setLegendBackgroundColor(Color.yellow);
legendProps.setLegendExistence (false);
GraphChart2DProperties graph2DProps = new GraphChart2DProperties();
GraphProperties graphProps = new GraphProperties();
object2DProps .setObjectTitleFontName("test");
Dataset dataset = new Dataset (1, hist.length, 1);
for(int i=0;i<hist.length;i++)
dataset.set (0, i, 0, hist[i]) ; 
LBChart2D lbChart2D = new LBChart2D();
lbChart2D.setObject2DProperties (object2DProps);
lbChart2D.setChart2DProperties (chart2DProps);
lbChart2D.setLegendProperties (legendProps);
lbChart2D.setGraphChart2DProperties (graph2DProps);
lbChart2D.addGraphProperties (graphProps);
lbChart2D.addDataset (dataset);
lbChart2D.setSize(width, height);
BufferedImage lbImage = lbChart2D.getImage();
jLabel15.setIcon(new ImageIcon(lbImage)); 

现在它产生一个异常 java.lang.NullPointerException 在这一行：

Now It produces an Exception java.lang.NullPointerException on this line:

BufferedImage lbImage = lbChart2D.getImage();

出了什么问题？

推荐答案

几个 Chart2D 演示包含在发行版中。您可以从 ImageIO 获得的 BufferedImage 中收集数据。另请参阅 jfreechart 。

Several Chart2D demos are included in the distribution. You can collect the data from a BufferedImage obtained via ImageIO. See also jfreechart.

附录：如果没有完整的示例，您可以使用 validate（）来获取调试消息。至少，验证您使用 hist.length 标签调用 setLabelsAxisLabelsTexts（）。

Addendum: Absent a complete example, you can use validate() to get debug messages. At a minimum, verify that you invoke setLabelsAxisLabelsTexts() with hist.length labels.

//Optional validation:  Prints debug messages if invalid only.
if (!chart2D.validate(false)) {
    chart2D.validate(true);
}

这篇关于使用Chart2D的直方图的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！