package-summary.html

Geotools是一个开源的Java GIS工具包,可利用它来开发符合标准的地理信息系统。Geotools提供了OGC(Open Geospatial Consortium)规范的一个实现来作为他们的

    <TABLE ALIGN="center" BORDER='3' CELLPADDING='6' BGCOLOR="F4F8FF">
      <TR BGCOLOR="#B9DCFF">
        <TH><A HREF="http://java.sun.com/j2se/1.4/docs/api/javax/imageio/ImageReader.html" title="class or interface in javax.imageio"><CODE>ImageReader</CODE></A> subclass</TH>
        <TH>Name</TH>
        <TH>MIME type</TH>
      </TR>
      <TR>
        <TD><A HREF="../../../../org/geotools/image/io/RawBinaryImageReader.html" title="class in org.geotools.image.io"><CODE>RawBinaryImageReader</CODE></A></TD>
        <TD>raw</TD>
        <TD>image/raw</TD>
      </TR>
      <TR>
        <TD><A HREF="../../../../org/geotools/image/io/TextMatrixImageReader.html" title="class in org.geotools.image.io"><CODE>TextMatrixImageReader</CODE></A></TD>
        <TD>matrix</TD>
        <TD>text/matrix</TD>
      </TR>
      <TR>
        <TD><A HREF="../../../../org/geotools/image/io/TextRecordImageReader.html" title="class in org.geotools.image.io"><CODE>TextRecordImageReader</CODE></A></TD>
        <TD>gridded records</TD>
        <TD>text/x-grid</TD>
      </TR>
    </TABLE>

    <P ALIGN="justify"><A HREF="../../../../org/geotools/image/io/SimpleImageReader.html" title="class in org.geotools.image.io"><CODE>SimpleImageReader</CODE></A> is
    the base class for image decoders reading stream with few (if any)
    meta-data. Examples of such streams are matrix containing the pixels
    values in a binary form (RAW images), or ASCII files containing values
    written as decimal numbers. Such kinds of stream are not uncommon in the
    remote sensing field. They often contain geophysical values (e.g.
    temperature in Celsius degrees, elevation in metres, etc.) better
    represented as floating point numbers than integers. For example,
    a user may want to read an ASCII file containing gridded elevation
    on the ocean floor (left side below). <A HREF="../../../../org/geotools/image/io/TextRecordImageReader.html" title="class in org.geotools.image.io"><CODE>TextRecordImageReader</CODE></A>
    can read such file, detect automatically minimum and maximum values (in order
    to scale the grayscale palette) and produce the image below:</P>

    <P ALIGN="justify"></P>
    <TABLE ALIGN="center" CELLPADDING='24'>
      <TR>
        <TD><PRE>
Longitude Latitude Altitude
59.9000   -30.0000   -3022
59.9333   -30.0000   -3194
59.9667   -30.0000   -3888
60.0000   -30.0000   -3888
45.0000   -29.9667   -2502
45.0333   -29.9667   -2502
45.0667   -29.9667   -2576
45.1000   -29.9667   -2576
45.1333   -29.9667   -2624
45.1667   -29.9667   -2690
45.2000   -29.9667   -2690
45.2333   -29.9667   -2692
45.2667   -29.9667   -2606
45.3000   -29.9667   -2606
45.3333   -29.9667   -2528
</PRE>etc...</TD>
        <TD>
          <IMG SRC="doc-files/Sandwell.jpeg">
        </TD>
      </TR>
    </TABLE>

    <P ALIGN="justify">By default, <A HREF="../../../../org/geotools/image/io/SimpleImageReader.html" title="class in org.geotools.image.io"><CODE>SimpleImageReader</CODE></A>
    store decoded image using data type <A HREF="http://java.sun.com/j2se/1.4/docs/api/java/awt/image/DataBuffer.html#TYPE_FLOAT" title="class or interface in java.awt.image"><CODE>DataBuffer.TYPE_FLOAT</CODE></A>
    and a grayscale color space. This politic produce image matching closely the
    original data, i.e. it involves as few transformations as possible. But
    displaying floating-point image is usually very slow. User are strongly
    encourages to use <A HREF="http://java.sun.com/products/java-media/jai/">Java
    Advanced Imaging</A>'s operations after reading in order to scale data as
    they see fit. The example below reformat the <A HREF="http://java.sun.com/j2se/1.4/docs/api/java/awt/image/DataBuffer.html#TYPE_FLOAT" title="class or interface in java.awt.image"><CODE>DataBuffer.TYPE_FLOAT</CODE></A>
    data into <A HREF="http://java.sun.com/j2se/1.4/docs/api/java/awt/image/DataBuffer.html#TYPE_BYTE" title="class or interface in java.awt.image"><CODE>DataBuffer.TYPE_BYTE</CODE></A> and change the grayscale
    colors to an indexed color model.</P>

    <P>&nbsp;</P>

<TABLE align="center" bgcolor="#F8F8F8" border="3" cellpadding="12"><TR><TD nowrap>
<PRE><FONT color="#0000A0">
import <A HREF="http://java.sun.com/products/java-media/jai/forDevelopers/jai-apidocs/javax/media/jai/JAI.html" title="class or interface in javax.media.jai"><CODE>javax.media.jai.JAI</CODE></A>;
import <A HREF="http://java.sun.com/products/java-media/jai/forDevelopers/jai-apidocs/javax/media/jai/ImageLayout.html" title="class or interface in javax.media.jai"><CODE>javax.media.jai.ImageLayout</CODE></A>;
import <A HREF="http://java.sun.com/j2se/1.4/docs/api/java/awt/RenderingHints.html" title="class or interface in java.awt"><CODE>java.awt.RenderingHints</CODE></A>;
import <A HREF="http://java.sun.com/j2se/1.4/docs/api/java/awt/image/DataBuffer.html" title="class or interface in java.awt.image"><CODE>java.awt.image.DataBuffer</CODE></A>;
import <A HREF="http://java.sun.com/j2se/1.4/docs/api/java/awt/image/IndexColorModel.html" title="class or interface in java.awt.image"><CODE>java.awt.image.IndexColorModel</CODE></A>;
import <A HREF="http://java.sun.com/j2se/1.4/docs/api/java/awt/image/renderable/ParameterBlock.html" title="class or interface in java.awt.image.renderable"><CODE>java.awt.image.renderable.ParameterBlock</CODE></A>;

<I><FONT color="#008000">// Omitting class and method declaration...</FONT></I>

<FONT color="#808080"><STRONG>
/*
 * Prepare the indexed color model. Arrays
 * R, G and B should contains 256 RGB values.
 */</STRONG></FONT>
final byte[] R=...
final byte[] G=...
final byte[] B=...
final IndexColorModel colors = new IndexColorModel(8, 256, R,G,B);
final ImageLayout     layout = new ImageLayout().setColorModel(colorModel);
final RenderingHints   hints = new RenderingHints(JAI.KEY_IMAGE_LAYOUT, layout);
<FONT color="#808080"><STRONG>
/*
 * Rescale the image.   First, all pixels values are transformed using
 * the equation pi=CO+C1*p. Then, type float is clamp to type byte and
 * the new index color model is set.   Displaying such an image should
 * be much faster.
 */</STRONG></FONT>
final double C0 = ...
final double C1 = ...
image = JAI.create("Rescale", new ParameterBlock().addSource(image).add(new double[]{C1}).add(new double[]{C0}));
image = JAI.create("Format",  new ParameterBlock().addSource(image).add(DataBuffer.TYPE_BYTE), hints);
</FONT></PRE></TD></TR></TABLE>
<P>

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