mainwzpixmaptest.html

Delaunay三角形的网格剖分程序

<TITLE>WZ 1.1: Reading pixmaps</TITLE>

<H1>Reading Pixmaps</H1>

<PRE>
#include "wzoutput.hxx"
#include "wzpixmap.hxx"
</PRE>

<H2>class wzTrueColorPixmap</H2>

The class <B>wzTrueColorPixmap</B> should be able to read true color
pictures in many formats.  At the current time, it allows to read only
the simplest pixmap format - <B>PPM</B>. Thus, you have to transfer
pictures from other formats into PPM using other programs. I use
<B>xv</B> for this purpose.

<PRE>
void main()
{
  wzTrueColorPixmap tmap("cog/pixmapinput.ppm");
  tmap.save("test.ppm"); // compare if they are identical
</PRE>

<H2>class wzColorTablePixmap</H2>

ls This class has a color table and indices into this color table.  The
maximal length of the color table is 256.  With lower number of
<B>maxcolors</B> the algorithm to identify similar colors in a true
color picture becomes faster. Instead of creating a
<B>wzColorTablePixmap</B> explicit from a <B>wzTrueColorPixmap</B> by

<PRE>
  int maxcolors=20;
  wzColorTablePixmap map(tmap,maxcolors);
  map.save("test2.ppm"); // compare if they are identical
</PRE>

you can immediately create it from a file, in this case the true color
pixmap is allocated only temporary

<PRE>
// wzColorTablePixmap map("pixmap.ppm",maxcolors);
</PRE>

How to use the resulting color table can be seen here:

<PRE>
 wzOutputDefault("&lt;&gt;")
	&lt;&lt; "Pixmap [" &lt;&lt; map.lx() &lt;&lt; ","&lt;&lt; map.ly()&lt;&lt;"] with "
  	&lt;&lt; map.colors() &lt;&lt; " colors\n";
 for(int i=1;i<=map.colors();i++){
        wzOutputDefault("&lt;&gt;")
       	&lt;&lt; i &lt;&lt; ": "&lt;&lt; map.color(i) &lt;&lt; "\n";
 }
</PRE>

A loop over the whole picture has to be organized in this way:

<PRE>
/*
  int ix,iy,index;
  wzColor color;
  for(ix=0;ix&lt;map.lx();ix++){
    for(iy=0;iy&lt;map.ly();iy++){
    	index = map(ix,iy);
    	color = map.color(index);
    }
  }
*/
</PRE>

<A NAME="End"> <hr></A>
<PRE>
  fine();
}
</PRE>

 <P>If you have a test file <I>wzpixmaptest.ppm</I>, you can test this
code with:
 <BR>
 <BR><B>&gt;cog main wzpixmap</B>
 <BR>
 <BR>The output should be something like
 <BR>Pixmap [250,248] with 5 colors
 <BR>1: #000000000
 <BR>2: #f00800800
 <BR>3: #800800f00
 <BR>4: #800f00f00
 <BR>5: #800f00800
 <BR>success
 <BR>