graphics rendering.htm

是一部关于java高级图像处理的的一本入门书

     }
</PRE>
  <HR>

  <P><A name=52230>
  <H3>10.2.3 <IMG src="Graphics Rendering.files/space.gif">Rendering Graphics 
  Primitives</H3></A>The <CODE>Graphics2D</CODE> class provides methods for 
  creating <CODE>Shape</CODE>s and <CODE>Text</CODE>, and for rendering 
  <CODE>Images</CODE>. <A 
  href="http://java.sun.com/products/java-media/jai/forDevelopers/jai1_0_1guide-unc/Graphics.doc.html#52234">Table 
  10-3</A> lists these methods.
  <P>
  <TABLE cellPadding=3 border=3>
    <CAPTION><FONT size=-1><B><A name=52234><I>Table 10-3 </I><IMG 
    src="Graphics Rendering.files/sm-blank.gif" border=0> Graphics Primitives 
    Methods </A></B></FONT></CAPTION>
    <TBODY>
    <TR vAlign=top>
      <TH><A name=52238>Method </A>
      <TH><A name=52240>Description </A>
    <TR vAlign=top>
      <TD><A name=52242>draw</A><BR>
      <TD><A name=52262>Strokes the outline of a Shape using the Stroke and 
        Paint settings of the current Graphics2D context.</A><BR>
    <TR vAlign=top>
      <TD><A name=52246>fill</A><BR>
      <TD><A name=52269>Fills the interior of a Shape using the Paint settings 
        of the Graphics2D context.</A><BR>
    <TR vAlign=top>
      <TD><A name=52250>drawString</A><BR>
      <TD><A name=52252>Renders the specified text string using the Paint 
        setting of the Graphics2D context.</A><BR>
    <TR vAlign=top>
      <TD><A name=52254>drawImage</A><BR>
      <TD><A name=52256>Renders the specified Image.</A><BR>
    <TR vAlign=top>
      <TD><A name=52286>drawRenderableImage</A><BR>
      <TD><A name=52288>Renders the specified RenderableImage.</A><BR>
    <TR vAlign=top>
      <TD><A name=52282>drawRenderedImage</A><BR>
      <TD><A name=52284>Renders the specified 
  RenderedImage.</A><BR></TR></TBODY></TABLE>
  <P><A name=52289>
  <H4>10.2.3.1 <IMG src="Graphics Rendering.files/space.gif">Drawing a 
  Shape</H4></A>The <CODE>Graphics2D.draw</CODE> method is used to render the 
  outline of any <CODE>Shape</CODE>. The <CODE>Graphics2D</CODE> class also 
  inherits draw methods from the <CODE>Graphics</CODE> class, such as 
  <CODE>drawLine</CODE>, <CODE>drawRect</CODE>, <CODE>drawRoundRect</CODE>, 
  <CODE>drawOval</CODE>, <CODE>drawArc</CODE>, <CODE>drawPolyline</CODE>, 
  <CODE>drawPolygon</CODE>, and <CODE>draw3DRect</CODE>. 
  <P>When a <CODE>Shape</CODE> is drawn, its path is stroked with the 
  <CODE>Stroke</CODE> object in the <CODE>Graphics2D</CODE> context. (See <A 
  href="http://java.sun.com/products/java-media/jai/forDevelopers/jai1_0_1guide-unc/Graphics.doc.html#51812">Section 
  10.2.2, "Stroke Attributes</A>," for more information.) By setting an 
  appropriate <CODE>BasicStroke</CODE> object in the <CODE>Graphics2D</CODE> 
  context, you can draw lines of any width or pattern. The 
  <CODE>BasicStroke</CODE> object also defines the line's endcap and join 
  attributes. 
  <P>To render a <CODE>Shape</CODE>'s outline: 
  <P>
  <UL>1. Create the <CODE>BasicStroke</CODE> object
    <P>2. Call <CODE>Graphics2D.setStroke</CODE>
    <P>3. Create the <CODE>Shape</CODE>
    <P>4. Call <CODE>Graphics2D.draw(shape)</CODE>
    <P></P></UL><A 
  href="http://java.sun.com/products/java-media/jai/forDevelopers/jai1_0_1guide-unc/Graphics.doc.html#52316">Listing 
  10-4</A> shows a code example in which a <CODE>GeneralPath</CODE> object is 
  used to define a star and a <CODE>BasicStroke</CODE> object is added to the 
  <CODE>Graphics2D</CODE> context to define the star's line width and join 
  attributes.
  <P><CAPTION><FONT size=-1><B><A name=52316>
  <CENTER><FONT size=-1><B><I>Listing 10-4 </I><IMG 
  src="Graphics Rendering.files/sm-blank.gif" border=0> Example Drawing a Shape 
  </B></FONT></CENTER></A>
  <P></B></FONT></CAPTION>
  <HR>
  <TR valign="top"><TD><PRE>     public void paint(Graphics g) {
        Graphics2D g2 = (Graphics2D) g;
</PRE><TR valign="top"><TD><PRE>        // Create and set the stroke.
        g2.setStroke(new BasicStroke(4.0f));
</PRE><TR valign="top"><TD><PRE>        // Create a star using a general path object.
        GeneralPath p new GeneralPath(GeneralPath.NON_ZERO);
        p.moveTo(- 100.0f, - 25.0f);
        p.lineTo(+ 100.0f, - 25.0f);
        p.lineTo(- 50.0f, + 100.0f);
        p.lineTo(+ 0.0f, - 100.0f);
        p.lineTo(+ 50.0f, + 100.0f);
        p.closePath();
</PRE><TR valign="top"><TD><PRE>        // Translate the origin towards the center of the canvas.
        g2.translate(100.0f, 100.0f);
</PRE><TR valign="top"><TD><PRE>        // Render the star's path.
        g2.draw(p);
     }
</PRE>
  <HR>

  <P><A name=52346>
  <H4>10.2.3.2 <IMG src="Graphics Rendering.files/space.gif">Filling a 
  Shape</H4></A>The <CODE>Graphics2D.fill</CODE> method is used to fill any 
  <CODE>Shape</CODE>. When a <CODE>Shape</CODE> is filled, the area within its 
  path is rendered with the <CODE>Paint</CODE> object in the Graphics2D context: 
  a <CODE>Color</CODE>, <CODE>TexturePaint</CODE>, or 
  <CODE>GradientPaint</CODE>. 
  <P>The <CODE>Graphics2D</CODE> class also inherits fill methods from the 
  <CODE>Graphics</CODE> class, such as <CODE>fillRect</CODE>, 
  <CODE>fill3DRect</CODE>, <CODE>fillRoundRect</CODE>, <CODE>FillOval</CODE>, 
  <CODE>fillArc</CODE>, <CODE>fillPolygon</CODE>, and <CODE>clearRect</CODE>. 
  <P>To fill a <CODE>Shape</CODE>: 
  <P>
  <UL>1. Set the fill color or pattern on the <CODE>Graphics2D</CODE> context 
    using <CODE>Graphics2D.setColor</CODE>, or <CODE>Graphics2DsetPaint</CODE>.
    <P>2. Create the <CODE>Shape</CODE>
    <P>3. Call <CODE>Graphics2D.fill</CODE> to render the <CODE>Shape</CODE>
    <P></P></UL><A 
  href="http://java.sun.com/products/java-media/jai/forDevelopers/jai1_0_1guide-unc/Graphics.doc.html#52394">Listing 
  10-5</A> shows a code example in which the <CODE>setColor</CODE> method is 
  called to define a green fill for a <CODE>Rectangle2D</CODE>.
  <P><CAPTION><FONT size=-1><B><A name=52394>
  <CENTER><FONT size=-1><B><I>Listing 10-5 </I><IMG 
  src="Graphics Rendering.files/sm-blank.gif" border=0> Example Filling a 
  Shape</B></FONT></CENTER></A>
  <P></B></FONT></CAPTION>
  <HR>
  <TR valign="top"><TD><PRE>     Public void paint(Graphics g) {
        Graphics2D g2 = (Graphics2D) g;
</PRE><TR valign="top"><TD><PRE>        g2.setpaint(Color.green);
        Rectangle2D r2 = new Rectangle2D.float(25, 25, 150, 150);
</PRE><TR valign="top"><TD><PRE>        g2.fill(r2);
     }
</PRE>
  <HR>

  <P><A name=52415>
  <H4>10.2.3.3 <IMG src="Graphics Rendering.files/space.gif">Rendering 
  Text</H4></A>The entire subject of fonts and text layout is too extensive to 
  try to describe here. In this section, we'll give a brief overview of the 
  <CODE>Graphics2D.drawString</CODE> method, which is used to render a text 
  string. 
  <P>There are two basic variations on the <CODE>drawString</CODE> method. Two 
  methods takes a <CODE>String</CODE> for an argument and two methods take an 
  <CODE>AttributedCharacterIterator</CODE>. If the argument is a 
  <CODE>String</CODE>, the current <CODE>Font</CODE> in the 
  <CODE>Graphics2D</CODE> context is used to convert the characters in the 
  <CODE>String</CODE> into a set of glyphs with whatever basic layout and 
  shaping algorithms the font implements. If the argument is an 
  <CODE>AttributedCharacterIterator</CODE>, the iterator is asked to convert 
  itself to a <CODE>TextLayout</CODE> using its embedded font attributes. The 
  <CODE>TextLayout</CODE> implements more sophisticated glyph layout algorithms 
  that perform Unicode I-directional layout adjustments automatically for 
  multiple fonts of differing writing directions. 
  <P>A third method used to render text is the 
  <CODE>Graphics2D.drawGlyphVector</CODE> method, which takes a 
  <CODE>GlyphVector</CODE> as an argument. The <CODE>GlyphVector</CODE> object 
  contains the appropriate font-specific glyph codes with explicit coordinates 
  for the position of each glyph. 
  <P>The character outlines are filled with the <CODE>Paint</CODE> object in the 
  Graphics2D context. 
  <P><A name=51398>
  <H2>10.3 <IMG src="Graphics Rendering.files/space.gif">Graphics2D 
  Example</H2></A><A 
  href="http://java.sun.com/products/java-media/jai/forDevelopers/jai1_0_1guide-unc/Graphics.doc.html#51518">Listing 
  10-6</A> shows a code sample for a Graphics2D example. 
  <P><CAPTION><FONT size=-1><B><A name=51518>
  <CENTER><FONT size=-1><B><I>Listing 10-6 </I><IMG 
  src="Graphics Rendering.files/sm-blank.gif" border=0> Graphics2D 
  Example</B></FONT></CENTER></A>
  <P></B></FONT></CAPTION>
  <HR>
  <TR valign="top"><TD><PRE>     // Read a RenderedImage and convert it to a BufferedImage.
     imagePath = new String("./images/sample.jpg");
     Image ai = loadAWTImage(imagePath, this);
     RenderedImage ri = JAI.create("awtimage", ai);
     BufferedImage bi = getBufferedImage(ri);
     RenderedImage targetImage = null;
     targetImage = new BufferedImage(bi.getWidth(),
                                     bi.getHeight(),
                                     bi.getType());
</PRE><TR valign="top"><TD><PRE>     // Create a Graphics2D object to draw into the BufferedImage.
     Graphics2D g2d = targetImage.createGraphics();
</PRE>
  <HR>

  <P><A name=51405>
  <H2>10.4 <IMG src="Graphics Rendering.files/space.gif">Adding Graphics and 
  Text to an Image</H2></A>The <CODE>java.awt.Graphics2D</CODE> class enables 
  you to draw lines, geometric shapes, images, and text. These objects can then 
  be "painted" over a <CODE>TiledImage</CODE>. 
  <P>
  <P>
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  &copy; 1999, Sun Microsystems, Inc. All rights reserved.</H5><!-- Last updated: Tue Nov 02 18:04:40 1999 --></BLOCKQUOTE>
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