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  <CODE>double</CODE>, or an <CODE>Object</CODE>. The 
  <CODE>setOperationName</CODE> method can be used to change the operation name. 
  The <CODE>setParameterBlock</CODE> method can be used to change the nodes's 
  <CODE>ParameterBlock</CODE>. 
  <P><A name=57755>
  <H4>3.3.3.2 <IMG 
  src="Programming in Java Advanced Imaging3.files/space.gif">Editing Renderable 
  Graphs</H4></A>Since Renderable graphs are not evaluated until there is a 
  specific request for a rendering, the nodes may be edited at any time. The 
  main concern with editing Renderable graphs is the introduction of cycles, 
  which must be avoided. 
  <P>The <CODE>RenderableOp</CODE> class provides several methods for 
  reconfiguring a Renderable node. The <CODE>setParameter</CODE> methods can be 
  used to set the node's parameters to a <CODE>byte</CODE>, <CODE>char</CODE>, 
  <CODE>short</CODE>, <CODE>int</CODE>, <CODE>long</CODE>, <CODE>float</CODE>, 
  <CODE>double</CODE>, or an <CODE>Object</CODE>. The 
  <CODE>setParameterBlock</CODE> method can be used to change the nodes's 
  <CODE>ParameterBlock</CODE>. The <CODE>setProperty</CODE> method can be used 
  to change a node's local property. The <CODE>setSource</CODE> method can be 
  used to set one of the node's sources to an <CODE>Object</CODE>. 
  <P><A name=56364>
  <H2>3.4 <IMG 
  src="Programming in Java Advanced Imaging3.files/space.gif">Remote 
  Execution</H2></A>Up to this point, we have been talking about standalone 
  image processing. JAI also provides for client-server image processing through 
  what is called the <EM>Remote Execution</EM> model. 
  <P>Remote execution is based on Java RMI (remote method invocation). Java RMI 
  allows Java code on a client to invoke method calls on objects that reside on 
  another computer without having to move those objects to the client. The 
  advantages of remote execution become obvious if you think of several clients 
  wanting to access the same objects on a server. To learn more about remote 
  method invocation, refer to one of the books on Java described in <A 
  href="http://java.sun.com/products/java-media/jai/forDevelopers/jai1_0_1guide-unc/Preface.doc.html#47778">"Related 
  Documentation" on page xv</A>. 
  <P>To do remote method invocation in JAI, a <CODE>RemoteImage</CODE> is set up 
  on the server and a <CODE>RenderedImage</CODE> chain is set up on the client. 
  For more information, see <A 
  href="http://java.sun.com/products/java-media/jai/forDevelopers/jai1_0_1guide-unc/Client-server.doc.html#47285">Chapter 
  12, "Client-Server Imaging</A>." 
  <P><A name=52603>
  <H2>3.5 <IMG src="Programming in Java Advanced Imaging3.files/space.gif">Basic 
  JAI API Classes</H2></A>JAI consists of several classes grouped into five 
  packages: 
  <P>
  <UL>
    <LI><CODE>javax.media.jai</CODE> - contains the "core" JAI interfaces and 
    classes
    <P></P></LI></UL>
  <UL>
    <LI><CODE>javax.media.jai.iterator</CODE> - contains special iterator 
    interfaces and classes, which are useful for writing extension operations
    <P></P></LI></UL>
  <UL>
    <LI><CODE>javax.media.jai.operator</CODE> - contains classes that describe 
    all of the image operators
    <P></P></LI></UL>
  <UL>
    <LI><CODE>javax.media.jai.widget</CODE> - contains interfaces and classes 
    for creating simple image canvases and scrolling windows for image display
    <P></P></LI></UL>Now, let's take a look at the most common classes in the JAI 
  class hierarchy. 
  <P><A name=52605>
  <H3>3.5.1 <IMG src="Programming in Java Advanced Imaging3.files/space.gif">The 
  JAI Class</H3></A>The <CODE>JAI</CODE> class cannot be instantiated; it is 
  simply a placeholder for static methods that provide a simple syntax for 
  creating Renderable and Rendered graphs. The majority of the methods in this 
  class are used to create a <CODE>RenderedImage</CODE>, taking an operation 
  name, a <CODE>ParameterBlock</CODE>, and <CODE>RenderingHints</CODE> as 
  arguments. There is one method to create a <CODE>RenderableImage</CODE>, 
  taking an operation name, a <CODE>ParameterBlock</CODE>, and 
  <CODE>RenderingHints</CODE> as arguments. 
  <P>There are several variations of the <CODE>create</CODE> method, all of 
  which take sources and parameters directly and construct a 
  <CODE>ParameterBlock</CODE> automatically. 
  <P><A name=52611>
  <H3>3.5.2 <IMG src="Programming in Java Advanced Imaging3.files/space.gif">The 
  PlanarImage Class</H3></A>The <CODE>PlanarImage</CODE> class is the main class 
  for describing two-dimensional images in JAI. <CODE>PlanarImage</CODE> 
  implements the <CODE>RenderedImage</CODE> interface from the Java 2D API. 
  <CODE>TiledImage</CODE> and <CODE>OpImage</CODE>, described later, are 
  subclasses of <CODE>PlanarImage</CODE>.<CODE></CODE> 
  <P>The <CODE>RenderedImage</CODE> interface describes a tiled, read-only image 
  with a pixel layout described by a <CODE>SampleModel</CODE> and a 
  <CODE>DataBuffer</CODE>. Each tile is a rectangle of identical dimensions, 
  laid out on a regular grid pattern. All tiles share a common 
  <CODE>SampleModel</CODE>. 
  <P>In addition to the capabilities offered by <CODE>RenderedImage</CODE>, 
  <CODE>PlanarImage</CODE> maintains source and sink connections between the 
  nodes of rendered graphs. Since graph nodes are connected bidirectionally, the 
  garbage collector requires assistance to detect when a portion of a graph is 
  no longer referenced from user code and may be discarded. 
  <CODE>PlanarImage</CODE> takes care of this by using the <EM>Weak References 
  API</EM> of Java 2. 
  <P>Any <CODE>RenderedImage</CODE>s from outside the API are "wrapped" to 
  produce an instance of <CODE>PlanarImage</CODE>. This allows the API to make 
  use of the extra functionality of <CODE>PlanarImage</CODE> for all images. 
  <P><A name=52625>
  <H3>3.5.3 <IMG src="Programming in Java Advanced Imaging3.files/space.gif">The 
  CollectionImage Class</H3></A><CODE>CollectionImage</CODE> is the abstract 
  superclass for four classes representing collections of 
  <CODE>PlanarImage</CODE>s: 
  <P>
  <UL>
    <LI><CODE>ImageStack</CODE> - represents a set of two-dimensional images 
    lying in a common three-dimensional space, such as CT scans or seismic 
    volumes. The images need not lie parallel to one another.
    <P></P></LI></UL>
  <UL>
    <LI><CODE>ImageSequence</CODE> - represents a sequence of images with 
    associated time stamps and camera positions. This class can be used to 
    represent video or time-lapse photography.
    <P></P></LI></UL>
  <UL>
    <LI><CODE>ImagePyramid</CODE> - represents a series of images of 
    progressively lesser resolution, each derived from the last by means of an 
    imaging operator.
    <P></P></LI></UL>
  <UL>
    <LI><CODE>ImageMIPMap</CODE> - represents a stack of images with a fixed 
    operational relationship between adjacent slices.
    <P></P></LI></UL><A name=52640>
  <H3>3.5.4 <IMG src="Programming in Java Advanced Imaging3.files/space.gif">The 
  TiledImage Class</H3></A>The <CODE>TiledImage</CODE> class represents images 
  containing multiple tiles arranged into a grid. The tiles form a regular grid, 
  which may occupy any rectangular region of the plane. 
  <P><CODE>TiledImage</CODE> implements the <CODE>WritableRenderedImage</CODE> 
  interface from the Java 2D API, as well as extending <CODE>PlanarImage</CODE>. 
  A <CODE>TiledImage</CODE> allows its tiles to be checked out for writing, 
  after which their pixel data may be accessed directly. <CODE>TiledImage</CODE> 
  also has a <CODE>createGraphics</CODE> method that allows its contents to be 
  altered using Java 2D API drawing calls. 
  <P>A <CODE>TiledImage</CODE> contains a tile grid that is initially empty. As 
  each tile is requested, it is initialized with data from a 
  <CODE>PlanarImage</CODE> source. Once a tile has been initialized, its 
  contents can be altered. The source image may also be changed for all or part 
  of the <CODE>TiledImage</CODE> using its <CODE>set</CODE> methods. In 
  particular, an arbitrary region of interest (ROI) may be filled with data 
  copied from a <CODE>PlanarImage</CODE> source. 
  <P>The <CODE>TiledImage</CODE> class includes a method that allows you to 
  paint a <CODE>Graphics2D</CODE> onto the <CODE>TiledImage</CODE>. This is 
  useful for adding text, lines, and other simple graphics objects to an image 
  for annotating the image. For more on the TiledImage class, see <A 
  href="http://java.sun.com/products/java-media/jai/forDevelopers/jai1_0_1guide-unc/Acquisition.doc.html#52363">Section 
  4.2.2, "Tiled Image</A>." 
  <P><A name=52693>
  <H3>3.5.5 <IMG src="Programming in Java Advanced Imaging3.files/space.gif">The 
  OpImage Class</H3></A>The OpImage class is the parent class for all imaging 
  operations, such as: 
  <P>
  <UL>
    <LI><CODE>AreaOpImage</CODE> - for image operators that require only a fixed 
    rectangular source region around a source pixel to compute each destination 
    pixel
    <P></P></LI></UL>
  <UL>
    <LI><CODE>PointOpImage</CODE> - for image operators that require only a 
    single source pixel to compute each destination pixel
    <P></P></LI></UL>
  <UL>
    <LI><CODE>SourcelessOpImage</CODE> - for image operators that have no image 
    sources
    <P></P></LI></UL>
  <UL>
    <LI><CODE>StatisticsOpImage</CODE> - for image operators that compute 
    statistics on a given region of an image, and with a given sampling rate
    <P></P></LI></UL>
  <UL>
    <LI><CODE>UntiledOpimage</CODE> - for single-source operations in which the 
    values of all pixels in the source image contribute to the value of each 
    pixel in the destination image
    <P></P></LI></UL>
  <UL>
    <LI><CODE>WarpOpImage</CODE> - for image operators that perform an image 
warp
    <P></P></LI></UL>
  <UL>
    <LI><CODE>ScaleOpImage</CODE> - for extension operators that perform image 
    scaling requiring rectilinear backwards mapping and padding by the 
    resampling filter dimensions<CODE></CODE>
    <P></P></LI></UL>The <CODE>OpImage</CODE> is able to determine what source 
  areas are sufficient for the computation of a given area of the destination by 
  means of a user-supplied <CODE>mapDestRect</CODE> method. For most operations, 
  this method as well as a suitable implementation of <CODE>getTile</CODE> is 
  supplied by a standard subclass of <CODE>OpImage</CODE>, such as 
  <CODE>PointOpImage</CODE> or <CODE>AreaOpImage</CODE>. 
  <P>An <CODE>OpImage</CODE> is effectively a <CODE>PlanarImage</CODE> that is 
  defined computationally. In <CODE>PlanarImage</CODE>, the <CODE>getTile</CODE> 
  method of <CODE>RenderedImage</CODE> is left abstract, and 
  <CODE>OpImage</CODE> subclasses override it to perform their operation. Since 
  it may be awkward to produce a tile of output at a time, due to the fact that 
  source tile boundaries may need to be crossed, the <CODE>OpImage</CODE> class 
  defines a <CODE>getTile</CODE> method to cobble (copy) source data as needed 
  and to call a user-supplied <CODE>computeRect</CODE> method. This method then 
  receives contiguous source <CODE>Rasters</CODE> that are guaranteed to contain 
  sufficient data to produce the desired results. By calling 
  <CODE>computeRect</CODE> on subareas of the desired tile, <CODE>OpImage</CODE> 
  is able to minimize the amount of data that must be cobbled. 
  <P>A second version of the <CODE>computeRect</CODE> method that is called with 
  uncobbled sources is available to extenders. This interface is useful for 
  operations that are implemented using <EM>iterators</EM> (see <A 
  href="http://java.sun.com/products/java-media/jai/forDevelopers/jai1_0_1guide-unc/Extension.doc.html#51261">Section 
  14.4, "Iterators</A>"), which abstract away the notion of tile boundaries. 
  <P><A name=52811>
  <H3>3.5.6 <IMG src="Programming in Java Advanced Imaging3.files/space.gif">The 
  RenderableOp Class</H3></A>The <CODE>RenderableOp</CODE> class provides a 
  lightweight representation of an operation in the Renderable space (see <A 
  href="http://java.sun.com/products/java-media/jai/forDevelopers/jai1_0_1guide-unc/Programming-environ.doc.html#55932">Section 
  3.3.2, "Renderable Graphs</A>"). <CODE>RenderableOp</CODE>s are typically 
  created using the <CODE>createRenderable</CODE> method of the <CODE>JAI</CODE> 
  class, and may be edited at will. <CODE>RenderableOp</CODE> implements the 
  <CODE>RenderableImage</CODE> interface, and so may be queried for its 
  rendering-independent dimensions. 
  <P>When a <CODE>RenderableOp</CODE> is to be rendered, it makes use of the 
  <CODE>OperationRegistry</CODE> (described in <A 
  href="http://java.sun.com/products/java-media/jai/forDevelopers/jai1_0_1guide-unc/Extension.doc.html#47227">Chapter 
  14</A>) to locate an appropriate <CODE>ContextualRenderedImageFactory</CODE> 
  object to perform the conversion from the Renderable space into a 
  <CODE>RenderedImage</CODE>. 
  <P><A name=52834>
  <H3>3.5.7 <IMG src="Programming in Java Advanced Imaging3.files/space.gif">The 
  RenderedOp Class</H3></A>The <CODE>RenderedOp</CODE> is a lightweight object 
  similar to <CODE>RenderableOp</CODE> that stores an operation name, 
  <CODE>ParameterBlock</CODE>, and <CODE>RenderingHints</CODE>, and can be 
  joined into a Rendered graph (see <A