Treemap Layout and Rendering
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Ithaka Treemap

Ithaka Treemap provides a framework for tree maps.


  • API separating layout and rendering
  • Squarified treemap layout builder
  • Rendering support for AWT and SWT


Here's a brief introduction the core interfaces and classes.

As a side note, the above image has been rendered from a layout computed by Ithaka Treemap.

TreemapContentProvider Interface

The TreemapContentProvider interface is used to describe the tree structure and layout properties.

Object[] getElements(Object input); // get root elements
Object[] getChildren(Object element); // get element children
boolean hasChildren(Object element); // leaf test
Object getParent(Object element); // get parent element
Object getValue(Object element); // get an elements's value
int getSize(Object element); // get size for element (cell size)
boolean hasFrame(Object element); // layout children with frame
int getChildrenBorder(Object element, int border); // border around children

An element is visible in the layout if it is a leaf (hasChildren(element) == false) or it has a frame (hasFrame(element) == true). Otherwise the element's cell in the layout will be totally covered by its children.

The values associated with elements (getValue(element)) will be stored in the layout so they're available when rendering the layout to determine labels and colors.

TreemapBuilder Interface

The content provider is all needed to perform a layout. A TreemapBuilder is used to create a treemap (i.e. the layout).

Treemap build(TreemapContentProvider content, Object input, int width, int height);

SquarifiedTreemapBuilder Class

The SquarifiedTreemapBuilder class implements TreemapBuilder, taking care about keeping the aspect ratio of cells in the layout close to one.

TreemapLabelProvider Interface

When rendering a treemap, labels can be placed into cells. The TreemapLabelProvider provides the API to specify those:

String getText(Object element, Object value); // label to place inside a cell
String getTooltipText(Object element, Object value); // optional tooltip label

TreemapColorProvider Interface

Color getForegroundColor(Object element, Object value); // label color
Color getForegroundShadowColor(Object element, Object value); // optional label shadow color
Color getBackgroundColor(Object element, Object value); // primary cell color
Color getBackgroundGradientColor(Object element, Object value); // optional cell gradient color
Color getHighlightColor(Object element, Object value); // cell selection color
Color getBorderColor(Object element, Object value); // border color

TreemapGraphics Interface

The TreemapGraphics interface provides all the methods required to actually draw a treemap. It is implemented by classes AWTTreemapGraphics and SWTTreemapGraphics. There's usually no need to implement your own.

TreemapRenderer Class

Having a TreemapLabelProvider and TreemapColorProvider, a treemap can be rendered.

TreemapRenderer(TreemapLabelProvider labelProvider, TreemapColorProvider colorProvider);
void render(TreemapGraphics graphics, Treemap layout);

TreemapWriter Interface

The TreemapWriter interface is a convenient image creation.

void write(Treemap layout, OutputStream output) throws IOException;

Again, there are implementations for AWT and SWT, taking a TreemapRenderer, image type and label font at construction time.


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Ithaka Treemap is available under the Apache License, Version 2.0.

(c) 2012 Odysseus Software