How to Annotate a .png File with Axes Using Java and JFreeChart?

How to Annotate a .png File with Axes Using Java

Annotating a .png image with axes is possible without relying on external software. Here's an approach that leverages Java's built-in capabilities and JFreeChart for advanced customization:

Creating the Chart Base

To begin, create a chart using JFreeChart's ChartFactory.createXYLineChart method. This establishes the basic chart structure with data, axes, and a title.

Customizing the Axes

Customizing the axes can enhance readability. For instance, you can set bounds for the range axis (representing values) using ValueAxis.setLowerBound().

Using a Custom Renderer

To customize the appearance of data points, create a custom renderer by extending XYLineAndShapeRenderer. This allows you to control various aspects, such as shape, color, and visibility.

Adding Data and Color Coding

Create a data set using XYSeriesCollection, consisting of series of data points. To color code the data points, override the getItemFillPaint method in the custom renderer and assign unique colors using the Hue-Saturation-Brightness (HSB) model.

Integration into the Chart

Set the custom renderer to the chart's XYPlot using plot.setRenderer(). Additionally, adjust other chart properties like line shape and outline paint as desired.

Example Implementation

The code snippet provided demonstrates the discussed approach with sample data and a custom renderer. It creates a chart with axes, custom-shaped and colored data points, and a custom legend.

Conclusion

This approach offers a comprehensive solution to annotating .png files with axes and labels using Java. By leveraging JFreeChart and a custom renderer, you can create visually appealing and informative graphs without the need for external software.

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