The Scientific Graphics Toolkit (A Technical Overview) Donald Denbo UW-JISAO/NOAA-PMEL

January 11, 2002NVODS/DODS Technical Workshop2 Introduction The Scientific Graphics Toolkit (SGT) is a collection of Java classes and interfaces to create graphical applications. SGT is a toolkit, not an application. Using SGT requires moderate Java programming skills. SGT does have several classes that make creating a graphical application easier, but using SGT does require producing code. With a modicum of effort a Java programmer can, using SGT, create graphical Java applications that are easy to use. SGT has had 5588 downloads to 2393 unique sites in 60 countries since March 2000 (as of Jan 7, 2002).

January 11, 2002NVODS/DODS Technical Workshop3 History Sgt was developed to allow a NOAAServer user to interactively preview data and overlay plots. Originally developed using jdk 1.0.3, now uses jdk 1.1.x. Next release will require jdk 1.2 or newer. Tutorial made available October 25, SGT release dates 1.0 – March 20, – March 14, – December 14, 2001

January 11, 2002NVODS/DODS Technical Workshop4 SGT Applications OceanShare a collaborative tool for distributed in situ data visualization Being customized for Fisheries-Oceanography use  (pdf paper) paper ncBrowse a netCDF file browser for local and remote netCDF files  (power point presentation) point presentation 3452 downloads to 1680 unique sites in 48 countries since February 2000 (as of Jan 7, 2002). Climate Data Portal client A distributed in-situ data application  (power point presentation) point presentation Although the CDPclient has not been publicly released, it has had 125 downloads to 51 unique sites in 6 countries.

January 11, 2002NVODS/DODS Technical Workshop5 Outline Demos and Examples Technical Issues Design philosophy & Goals Using standard Java idioms Design Patterns Architecture Real world applications using SGT

January 11, 2002NVODS/DODS Technical Workshop6 Outline Demos and Examples (applet demo)applet demo Technical Issues Design philosophy & Goals Using standard Java idioms Design Patterns Architecture Real world applications using SGT

January 11, 2002NVODS/DODS Technical Workshop7 TAOMap Plot built from basic sgt components Uses ValueIcon, which implements DraggableValueIcon Draggable Uses a Point Key, which implements Moveable and Selectable Moveable Selectable

January 11, 2002NVODS/DODS Technical Workshop8 JRealTimeDemo Built from basic sgt components. Data class uses PropertyChangeEven ts to notify sgt. Sgt then updates plot.

January 11, 2002NVODS/DODS Technical Workshop9 JVectorDemo Uses JPlotLayout which provides:JPlotLayout Zoom LayerChild selection LayerChild Vector head style is HEAD, where vector head is unscaled.

January 11, 2002NVODS/DODS Technical Workshop10 JGridDemo Uses JPlotLayout which provides:JPlotLayout Zoom LayerChild selection LayerChild GridAttribute GridAttribute is initially set to RASTER_CONTOUR style.

January 11, 2002NVODS/DODS Technical Workshop11 Outline Demos and Examples Technical Issues Design philosophy & Goals Using standard Java idioms Design Patterns Architecture Real world applications using SGT

January 11, 2002NVODS/DODS Technical Workshop12 Design Philosophy & Goals Don’t provide too much functionality in the toolkit Require developer to disambiguate zoom request (which layer) Use interfaces for data model specification Hide as much of the internal machinery as possible Provide utility classes to support developer Dialogs to set/edit graphics properties Plot layout class to support simple graphics Basic implementations of data model interfaces Keep toolkit flexible and extensible GIS style layer approach Support several display types Time series/Time axes X-Y plot 2-D contour and “pixel” plots Vector plot Point-Value plot

January 11, 2002NVODS/DODS Technical Workshop13 Using standard Java idioms (don’t reinvent the wheel) Basic graphics toolkits AWT support (now being deprecated)  Pane is a container  Printing Swing support  Scrolling  Printing  Repaint (refresh)  Minimum, maximum, and preferred size  JPane is a container JavaBeans idiom  Use set/get for parameters  Use add/remove for event listeners  Use set/is for boolean parameters

January 11, 2002NVODS/DODS Technical Workshop14 Don’t reinvent the wheel (cont…) Events Mouse events  Trapped by SGT Object selection Object move/drag operations Zoom rectangle handling  Passed on by SGT All others… SGT internal events (not really events!)  Add/remove SGT components  Modify component appearance (eg. Label, axis) Property change events  When a property changes value (eg. LineAttribute)LineAttribute  When a value changes in a data object  When the range of a data object changes

January 11, 2002NVODS/DODS Technical Workshop15 Design Patterns Strategy. Define a family of algorithms, encapsulate each one, and make them interchangeable. Transform, TimeAxisStyle, CartesianRenderer TransformTimeAxisStyleCartesianRenderer Proxy. Provide a surrogate or placeholder for another object to control access to it. Pane, JPane PaneJPane Abstract Factory. Provide an interface for creating families of related or dependent objects without specifying their concrete classes. CartesianRenderer, GridCartesianRenderer, LineCartesianRenderer, VectorCartesianRenderer, PointCartesianRenderer CartesianRendererGridCartesianRenderer LineCartesianRendererVectorCartesianRenderer PointCartesianRenderer

January 11, 2002NVODS/DODS Technical Workshop16 More Design Patterns Interface. Keep a class that uses data and services provided by instances of other classes independent of those classes by having it access those instances through an interface. SGTData, SGTGrid, SGTLine, etc SGTDataSGTGridSGTLine IndexedColor, TransformColor, TransformAccess IndexedColorTransformColorTransformAccess LayerChild, Moveable, Selectable, Draggable LayerChildMoveableSelectableDraggable Façade. Provide a unified interface to a set of interfaces in a subsystem. JPlotLayout

January 11, 2002NVODS/DODS Technical Workshop17 Outline Demos and Examples Technical Issues Design philosophy & Goals Using standard Java idioms Design Patterns Architecture Real world applications using SGT

January 11, 2002NVODS/DODS Technical Workshop18 Core Architecture Three coordinate systems Device – lowest level in pixels Physical – lower-left origin User – user defined Three main components Pane/JPane – extends Container/JLayeredPane Layer – physical units, used to build plot Graph – user units, axes, renders data (presently only CartesianGraph is implemented)

January 11, 2002NVODS/DODS Technical Workshop19 Core structure

January 11, 2002NVODS/DODS Technical Workshop20 Layers Contain a single Graph object and many LayerChild objects. Many Layers can be associated with a single Pane Layers can share AxisTransforms via their CartesianGraph objects LayerChild objects use physical coordinates

Layer Children

January 11, 2002NVODS/DODS Technical Workshop22 Rendering data A CartesianGraph object aggregates: Zero or more X or Y axes A renderer appropriate for the data type and attribute (e.g., PointCartesianRenderer, LineCartesianRenderer, or GridCartesianRenderer) One X AxisTransform One Y AxisTransform AxisTransforms provide a user to physical coordinate transformation for space or time

Graph and Renderers

January 11, 2002NVODS/DODS Technical Workshop24 Space and Time Axes SpaceAxis provides a visual scale for the spatial user to physical coordinate transform TimeAxis creates a visual scale for the GeoDate to physical coordinate transform TimeAxis has several “styles” that can be used depending on the temporal span Minute-Hour Hour-Day Day-Month Month-Year Year-Decade

Axes and AxisStyles

January 11, 2002NVODS/DODS Technical Workshop26 Sgt Data Model Data model needs to Support X-Y, contour, raster, vector, and point plots Be compact and “light-weight” Throw events to notify applications of data and/or range changes. Accomplished the above by Supporting “plottable” objects  One- and two-dimensional arrays  Coordinate information  Units and titles Data model implemented using java interfaces

Sgt Data Model

January 11, 2002NVODS/DODS Technical Workshop28 Mouse Events Mouse events are pre-processed by Pane Events passed to the user are Object selection Zoom rectangle selected PropertyChangeEvents thrown are objectSelected zoomRectangle Events processed by sgt are Object move Object drag

January 11, 2002NVODS/DODS Technical Workshop29 Outline Demos and Examples Technical Issues Design philosophy & Goals Using standard Java idioms Design Patterns Architecture Real world applications using SGT

January 11, 2002NVODS/DODS Technical Workshop30 ncBrowse ncBrowse was developed to browse netCDF files. Uses JPlotLayout which provides: Zoom LayerChild selection

January 11, 2002NVODS/DODS Technical Workshop31 Client developed to plot data from distributed data servers. Data from multiple servers can be combined on a single plot. Uses JPlotLayout Line Plots Area Plots Climate Data Portal Client

January 11, 2002NVODS/DODS Technical Workshop32 OceanShare OceanShare provides Collaborative work environment Local and network access of data sets Access to Habanero tools (whiteboard, chat, etc.) Implemented using LineProfileLayout Line style (highlight, mark, or solid) Line color Interactive zoom UserIcon and ValueIcon (implements LayerChild interface)

January 11, 2002NVODS/DODS Technical Workshop33 What next? Finish GridAttributeDialog. (enables GridAttribute, contour, and ColorMap editing.) Next version (2.2) will use Java2D to provide native support of physical to device coordinate transformation Remove deprecated classes and drop jdk1.1 support

January 11, 2002NVODS/DODS Technical Workshop34 Real World Applications using SGT SGT – Java graphics toolkit A Tutorial of the Scientific Graphics Toolkit, NOAATech A Tutorial of the Scientific Graphics Toolkit “Interactive Graphics Toolkit for Java Applications and Web Applets”, American Meteorological Society paper, January “Interactive Graphics Toolkit for Java Applications and Web Applets”, SGT home page. ncBrowse – netCDF file browser ncBrowse home page. OceanShare – collaborative tool for distributed in-situ data “OceanShare: Interactive Access to Distributed In Situ Data in a Collaborative Tool Environment”, American Meteorological Society paper, January “OceanShare: Interactive Access to Distributed In Situ Data in a Collaborative Tool Environment”, GOIN 99 Presentation. Climate Data Portal – distributed in-situ data access Climate Data Portal home page.