gbcontourplot

Capabilities

gbcontourplot is a library written in Java (11). It allows for plotting isolines and isobands. Among other options, one can define - at least to some extent - the "region function" specifying the area on which the contours are visible, several color mappings and export to raster and vector formats are supported. Behind the scenes, it is the Marching Squares algorithm.

Motivation

During my graduate studies I needed to create contour plots restricted to certain areas, varying from simple circles to areas restricted by inequalities like y <= 1 + tan[ atan( 1 / cos t ) / 2 ] * cos t, where parameter t belongs to [- pi / 2, pi / 2]. Besides that, the plots needed to satisfy journal printing quality criteria. The only tool that worked the way I wished was one of the Computer Algebra Systems. These days I think about commercializing my know-how, but since I am no longer eligible for a free (cheap) university (student) licence, I need a replacement. Paying for a super expensive commercial license and use the CAS for plotting only would not be a wise way of spending money :)

Disclaimer

Although I put an effort to provide as clear syntax as possible, there is probably a lot of space for improvements. The library was intended to fully support several use cases rather than to be a general purpose tool. Still, I would be happy if you find it useful (with or without some adjustments). Please share you thoughts -> kglowinski at ymail dot com

Example

Java code for creating a ContourPlot (extending JPanel) is usually divided into two steps. First, we create the plot itself:

List<Function2DValue> dataPoints = readDataPoints(ERROR_DATA);
Grid2DInterpolator interpolator = Grid2DInterpolator.from(dataPoints).withMaxNearest(7);
Grid2DValues gridValues = interpolator.interpolateOnGrid(-1, 1, -1, 1, 100, 100);
ColorMapper colorMapper = new TableBasedColorMapper(ColorMapTable.GRAY_YELLOW.name());
List<LineEnds> isoLines = gridValues.toIsoLines(4);
List<ColoredPolygon> isoBands = gridValues.toIsoBands(4, colorMapper);

ContourPlot contourPlot = new ContourPlot(-1, 1, -1, 1)
    .setBottomMargin(100)
    .setTopMargin(20)
    .setLeftMargin(20)
    .setRightMargin(20)
    .setContourWidth(400)
    .setContourHeight(400)
    .setBackgroundAndClear(WHITE)
    .addIsoBands(isoBands, insideCircle(1), INCLUSIVE)
    .addIsoLines(isoLines, DARK_GRAY, new BasicStroke(0.5f), insideCircle(1), EXCLUSIVE)
    .addCircularMargin()
    .addDashedCircumference()
    .addHexagonalAxes();

Then, we add a color bar:

ColorBarBuilder colorBarBuilder = new ColorBarBuilder()
    .grid2DValues(gridValues)
    .setAutoIsoLevels(4)
    .labelLevels(asList(0.5, 0.6, 0.7, 0.8))
    .colorMapper(colorMapper)
    .colorBarLocation(BOTTOM)
    .left(20)
    .bottom(50)
    .width(400)
    .height(30)
    .font(new Font("DejaVu Sans Condensed", Font.PLAIN, 32))
    .floatingPointTemplate("%.1f")
    .barLabelSpacing(0)
    .continuous(true);

contourPlot.add(colorBarBuilder.build());

More examples can be found in demo directory/package.

Features

• Levels for isolines and isobands can be adjusted automatically or specified manually
• Several color maps are supported: INFERNO, MAGMA, VIRIDIS, PLASMA, GRAY_YELLOW, RAINBOW, DARK_RAINBOW, PARULA, CIVIDIS, RED_BLUE, TEMPERATURE
• In color bar, levels can be discrete or continuous, ticks and labels can be customized.
• Plots can be exported to raster and vector formats.
• Several hacks specific for the grain boundaries domain are added.
• Size of contour is adjustable.

Gallery

• Several plots with common scale. Discrete color bar.

- Different color maps. Continuous scale bars.

- Custom ticks and labels

License

GNU GPLv3