The Scientific Graphics Toolkit A Technical Overview

1
TheScientific Graphics Toolkit(A Technical
Overview)

• Donald Denbo
• UW-JISAO/NOAA-PMEL

http//www.epic.noaa.gov/java/sgt
2
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).

3
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, 2001.
• SGT release dates
• 1.0 March 20, 2000
• 2.0 March 14, 2001
• 2.1 December 14, 2001

4
SGT Applications

• OceanShare
• a collaborative tool for distributed in situ data
  visualization
• Being customized for Fisheries-Oceanography use
• http//www.epic.noaa.gov/collab/ (pdf paper)
• ncBrowse
• a netCDF file browser for local and remote netCDF
  files
• http//www.epic.noaa.gov/java/ncBrowse/ (power
  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
• http//www.epic.noaa.gov/cdp/ (power point
  presentation)
• Although the CDPclient has not been publicly
  released, it has had 125 downloads to 51 unique
  sites in 6 countries.

5
Outline

• Demos and Examples
• Technical Issues
• Design philosophy Goals
• Using standard Java idioms
• Design Patterns
• Architecture
• Real world applications using SGT

6
Outline

• Demos and Examples (applet demo)
• Technical Issues
• Design philosophy Goals
• Using standard Java idioms
• Design Patterns
• Architecture
• Real world applications using SGT

7
TAOMap

• Plot built from basic sgt components
• Uses ValueIcon, which implements Draggable
• Uses a Point Key, which implements Moveable and
  Selectable

http//www.epic.noaa.gov/java/sgt/sgt_demos.shtml
8
JRealTimeDemo

• Built from basic sgt components.
• Data class uses PropertyChangeEvents to notify
  sgt.
• Sgt then updates plot.

9
JVectorDemo

• Uses JPlotLayout which provides
• Zoom
• LayerChild selection
• Vector head style is HEAD, where vector head is
  unscaled.

http//www.epic.noaa.gov/java/sgt/sgt_demos.shtml
10
JGridDemo

• Uses JPlotLayout which provides
• Zoom
• LayerChild selection
• GridAttribute is initially set to RASTER_CONTOUR
  style.

http//www.epic.noaa.gov/java/sgt/sgt_demos.shtml
11
Outline

• Demos and Examples
• Technical Issues
• Design philosophy Goals
• Using standard Java idioms
• Design Patterns
• Architecture
• Real world applications using SGT

12
Design Philosophy Goals

• Dont 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

13
Using standard Java idioms(dont 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

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Dont 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)
• When a value changes in a data object
• When the range of a data object changes

15
Design Patterns

• Strategy. Define a family of algorithms,
  encapsulate each one, and make them
  interchangeable.
• Transform, TimeAxisStyle, CartesianRenderer
• Proxy. Provide a surrogate or placeholder for
  another object to control access to it.
• Pane, JPane
• Abstract Factory. Provide an interface for
  creating families of related or dependent objects
  without specifying their concrete classes.
• CartesianRenderer, GridCartesianRenderer,
  LineCartesianRenderer, VectorCartesianRenderer,
  PointCartesianRenderer

16
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
• IndexedColor, TransformColor, TransformAccess
• LayerChild, Moveable, Selectable, Draggable
• Façade. Provide a unified interface to a set of
  interfaces in a subsystem.
• JPlotLayout

17
Outline

• Demos and Examples
• Technical Issues
• Design philosophy Goals
• Using standard Java idioms
• Design Patterns
• Architecture
• Real world applications using SGT

18
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)

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Core structure
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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

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Layer Children
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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

23
Graph and Renderers
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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

25
Axes and AxisStyles
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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

27
Sgt Data Model
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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

29
Outline

• Demos and Examples
• Technical Issues
• Design philosophy Goals
• Using standard Java idioms
• Design Patterns
• Architecture
• Real world applications using SGT

30
ncBrowse

• ncBrowse was developed to browse netCDF files.
• Uses JPlotLayout which provides
• Zoom
• LayerChild selection

http//www.epic.noaa.gov/java/ncBrowse
31
Climate Data Portal Client

• 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

http//www.epic.noaa.gov/cdp/
32
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)

http//www.epic.noaa.gov/collab/
33
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

34
Real World Applications using SGT

• SGT Java graphics toolkit
• A Tutorial of the Scientific Graphics Toolkit,
  NOAATech 2002.
• Interactive Graphics Toolkit for Java
  Applications and Web Applets, American
  Meteorological Society paper, January 2001.
• 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 2000.
• GOIN 99 Presentation.
• Climate Data Portal distributed in-situ data
  access
• Climate Data Portal home page.