ch32.htm

《Perl 5 Unreleased》

&nbsp;31 #&nbsp;&nbsp;&nbsp;$incr = increment<BR>
&nbsp;32 #&nbsp;&nbsp;&nbsp;$maxAngle = up to this angle.<BR>
&nbsp;33<BR>
&nbsp;34 sub tree {<BR>
&nbsp;35&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;my ($h,$x,$y,$theta,$flen)
= @_; # local variables<BR>
&nbsp;36&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;my ($nx,$ny,$nlen,$mycolor);&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;#
for drawing to.<BR>
&nbsp;37&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;my ($i,$incr,$startAngle,$maxAngle);
# for the fanout<BR>
&nbsp;38&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;my ($randFans);<BR>
&nbsp;39<BR>
&nbsp;40&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;#<BR>
&nbsp;41&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;# Stopping conditions first.
<BR>
&nbsp;42&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;#<BR>
&nbsp;43&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if ($h &lt; 1) {<BR>
&nbsp;44&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;$im-&gt;filledRectangle($x-1,$base_y+$y-1,$x+2,$base_y+$y+2,$leaf);
<BR>
&nbsp;45&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;return
0; }<BR>
&nbsp;46&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;$nlen = $flen * $fanRatio;
<BR>
&nbsp;47&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if ($nlen &lt; 1) { return
0;}<BR>
&nbsp;48<BR>
&nbsp;49&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;$mycolor = $brown;<BR>
&nbsp;50&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if ($h == 2) { $mycolor
= $color3; }<BR>
&nbsp;51&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if ($h == 3) { $mycolor
= $color2; }<BR>
&nbsp;52&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if ($h == 4) { $mycolor
= $color1; }<BR>
&nbsp;53&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if ($h == 5) { $mycolor
= $color0; }<BR>
&nbsp;54&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;#<BR>
&nbsp;55&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;# Important!!!<BR>
&nbsp;56&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;#<BR>
&nbsp;57&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;$h -= 1;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;#
for recursion<BR>
&nbsp;58<BR>
&nbsp;59<BR>
&nbsp;60&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;$maxAngle = $theta + $fanAngle;
<BR>
&nbsp;61&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;$incr = ($maxAngle)/($maxfans
+ int(rand() * 3));<BR>
&nbsp;62<BR>
&nbsp;63&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;$startAngle = $theta - ($fanAngle/2);
<BR>
&nbsp;64<BR>
&nbsp;65&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if ($startAngle &lt; $NPIBY2)
{ $startAngle = $NPIBY2; }<BR>
&nbsp;66&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if ($startAngle &gt; $NPIBY2)
{ $startAngle = $PIBY2;&nbsp;}<BR>
&nbsp;67<BR>
&nbsp;68&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;# printf &quot;\n From %5.1f
--&gt; %5.1f, incr %5.1f&quot;,<BR>
&nbsp;69&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;#&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;$startAngle,$maxAngle,
$incr;<BR>
&nbsp;70<BR>
&nbsp;71&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;for ($i = $startAngle ;
$i &lt; $maxAngle; $i += $incr)<BR>
&nbsp;72&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;{
<BR>
&nbsp;73&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;$nx
= $nlen * sin($i);<BR>
&nbsp;74&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;$ny
= $nlen * cos($i);<BR>
&nbsp;75&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;#
<BR>
&nbsp;76&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;#
<BR>
&nbsp;77&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;#
<BR>
&nbsp;78&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;$im-&gt;line($x,$base_y+$y,$nx+$x,$base_y+$ny+$y,$mycolor);
<BR>
&nbsp;79&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;tree($h,$nx+$x,$ny+$y,$i,$nlen);
<BR>
&nbsp;80&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}
<BR>
&nbsp;81&nbsp;}<BR>
&nbsp;82<BR>
&nbsp;83 $height = 300;<BR>
&nbsp;84 $width&nbsp;&nbsp;= 300;<BR>
&nbsp;85 $maxfans = 3;<BR>
&nbsp;86 $maxdepth = 6;<BR>
&nbsp;87 $fanAngle = deg2rad(120);&nbsp;&nbsp;&nbsp;# Maximum
120 degrees<BR>
&nbsp;88 $fanRatio = 0.65;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;#
Each new branch is 4/5 of old.<BR>
&nbsp;89 $base_y = $height / 2;<BR>
&nbsp;90 #<BR>
&nbsp;91 #<BR>
&nbsp;92 #<BR>
&nbsp;93 $start_x = $width/2;<BR>
&nbsp;94 $start_y = 25;<BR>
&nbsp;95 $start_length = 80;<BR>
&nbsp;96 $start_angle = deg2rad(80);<BR>
&nbsp;97<BR>
&nbsp;98 srand(time);<BR>
&nbsp;99<BR>
100 use GD;<BR>
101<BR>
102 $im = new GD::Image(300,300);<BR>
103 $backgd = $im-&gt;colorAllocate(154,192,205);<BR>
104 $white = $im-&gt;colorAllocate(255, 255, 255);<BR>
105 $black = $im-&gt;colorAllocate(0, 0, 0);<BR>
106 $brown = $im-&gt;colorAllocate(188,130, 130);<BR>
107 $leaf&nbsp;&nbsp;= $im-&gt;colorAllocate(157,255,12);<BR>
108 $color0 = $im-&gt;colorAllocate(245,196,90);<BR>
109 $color1 = $im-&gt;colorAllocate(95,158,60);<BR>
110 $color2 = $im-&gt;colorAllocate(46,139,87);<BR>
111 $color3 = $im-&gt;colorAllocate(152,251,152);<BR>
112 $red = $im-&gt;colorAllocate(255,0,0);<BR>
113 $blue = $im-&gt;colorAllocate(0,0,255);<BR>
114 $im-&gt;transparent($white);&nbsp;&nbsp;&nbsp;&nbsp;# white
color is transparent<BR>
115 $im-&gt;interlaced(1);&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;#
cool venetian blinds effect<BR>
116<BR>
117 tree ($maxdepth,$start_x,$start_y,$start_angle,$start_length);
<BR>
118<BR>
119<BR>
120 $text_y = $base_y / 2 + $width / 2;<BR>
121 $text_x = $width / 5;<BR>
122 $infoStr = &quot;Welcome to Kamran's Home Page&quot;;<BR>
123 $dateStr = &quot;Today is &quot; . `date`;<BR>
124 $message = &quot;&nbsp;&nbsp;http://www.ikra.com/index.html&quot;;
<BR>
125<BR>
126 $im-&gt;string(gdLargeFont,$text_x,$text_y,$infoStr,$red);
<BR>
127 $im-&gt;string(gdSmallFont,$text_x,$text_y + 30,$dateStr,$blue);
<BR>
128 $im-&gt;stringUp(gdLargeFont,10,$height - 10,$message,$blue);
<BR>
129<BR>
130<BR>
131 # print the image to stdout<BR>
132<BR>
133 $|=1;<BR>
134<BR>
135 print &quot;Content-type: image/gif \n\n&quot;;<BR>
136 print $im-&gt;gif;</FONT></TT>
</BLOCKQUOTE>
<HR>
<P>
Lines 4 through 12 define some of the constants for using degrees
and radians. The script uses the following global variables:
<UL>
<LI><TT><FONT FACE="Courier">$height</FONT></TT> and <TT><FONT FACE="Courier">$width</FONT></TT>
are the extents of the image.
<LI><TT><FONT FACE="Courier">$maxfans</FONT></TT> is the maximum
number of sub-branches allowed per branch.
<LI><TT><FONT FACE="Courier">$fanAngle</FONT></TT> is the angle
where each new sub-branch is created.
<LI><TT><FONT FACE="Courier">$fanRatio</FONT></TT> is the ratio
of the length of the new branch to the length of its parent branch.
</UL>
<P>
Each call to the recursive function, <TT><FONT FACE="Courier">tree()</FONT></TT>,
uses the following variables:
<UL>
<LI><TT><FONT FACE="Courier">$h</FONT></TT> is the current depth
in recursion.
<LI><TT><FONT FACE="Courier">$x</FONT></TT> is the current <TT><FONT FACE="Courier">x</FONT></TT>
to draw from.
<LI><TT><FONT FACE="Courier">$y</FONT></TT> is the current <TT><FONT FACE="Courier">y</FONT></TT>
to draw from.
<LI><TT><FONT FACE="Courier">$theta</FONT></TT> is the angle to
start drawing from.
<LI><TT><FONT FACE="Courier">$flen</FONT></TT>is the length of
the current branch.
</UL>
<P>
If the depth is <TT><FONT FACE="Courier">1</FONT></TT> or less,
the <TT><FONT FACE="Courier">tree()</FONT></TT> function draws
a rectangle at the current location and backs out of the recursion.
See lines 43 and 44. It also backs out without drawing a leaf
if the new branch is too small to draw.
<P>
Different colors are used based on the depth of the recursion
in lines 49 through 53.
<P>
Line 57 is where the depth of the recursion is marked off. The
value of <TT><FONT FACE="Courier">$h</FONT></TT> is decremented
before a recursive call to <TT><FONT FACE="Courier">tree()</FONT></TT>
is made. Lines 60 to 66 make sure that the <I>fanout</I> (maximum
number of degrees between the outer most branches) and number
of sub-branches is set in the correct <TT><FONT FACE="Courier">-PI/2</FONT></TT>
to <TT><FONT FACE="Courier">+PI/2</FONT></TT> range. You may want
to customize these lines to see how you want your tree to &quot;grow.&quot;
<P>
At line 71 we use a <TT><FONT FACE="Courier">for</FONT></TT> loop
to make a recursive call to the <TT><FONT FACE="Courier">tree()</FONT></TT>
function with different fanout angles, locations to draw, and
colors.
<P>
The initialization of global variables is done from lines 83 to
98. The random number generator is seeded at line 98.
<P>
The image is created at line 102, with colors for its components
created in lines 103 to 115. The <TT><FONT FACE="Courier">tree()</FONT></TT>
function is called at line 117. Add more calls to <TT><FONT FACE="Courier">tree()</FONT></TT>
if you want more than one tree printed. Some text is drawn in
the image area to customize the output in the lines up to 131.
<P>
Lines 133 to 136 actually print the image to standard output as
the response to an HTTP request.
<P>
To use the previous listing in an HTML file, you can add this
tag to an HTML page:
<BLOCKQUOTE>
<TT>&lt;IMG SRC=&quot;http://www.ikra.com/cgi-bin/tree.pl&quot;&gt;</TT>
</BLOCKQUOTE>
<P>
The browser showing the HTML page will call the <TT><FONT FACE="Courier">tree.pl</FONT></TT>
script, which in turn will return the GIF image back. Therefore,
every time you reload the Web page, you'll see a new image. Neat.
Actually, you can also refer to the <TT><FONT FACE="Courier">tree.pl</FONT></TT>
in the Location prompt on your browser. Refer to Figure 32.5 to
see how it's referred to in a URL. The script is called <TT><FONT FACE="Courier">fractal.pl</FONT></TT>
in Figure 32.5.
<P>
<A HREF="f32-5.gif" tppabs="http://www.mcp.com/815097600/0-672/0-672-30891-6/f32-5.gif" ><B>Figure 32.5 : </B><I>Dynamic image creating with Web pages.</I></A>
<P>
You can see how easy it is to create GIF images on-the-fly and
use them in Web pages. Using the <TT><FONT FACE="Courier">GD.pm</FONT></TT>
module, it's easy to have Perl write your output as a GIF file
for use in other applications.
<H2><A NAME="Summary"><B><FONT SIZE=5 COLOR=#FF0000>Summary</FONT></B></A>
</H2>
<P>
In this chapter I covered two ways of creating images: using <TT><FONT FACE="Courier">gnuplot</FONT></TT>
and directly through the use of the <TT><FONT FACE="Courier">GD.pm</FONT></TT>
module. The <TT><FONT FACE="Courier">gnuplot</FONT></TT> method
is simpler to use when you have a set of data points in a logical
order that can be read directly from within <TT><FONT FACE="Courier">gnuplot</FONT></TT>.
An example for using <TT><FONT FACE="Courier">gnuplot</FONT></TT>
is when drawing charts and 3D plots. If you are drawing more than
just charts and plots, consider generating the images directly
from within Perl by using the <TT><FONT FACE="Courier">GD.pm</FONT></TT>
module. Using <TT><FONT FACE="Courier">GD.pm</FONT></TT> is a
bit more difficult because you have to manage the details of drawing
yourself, but it does eliminate the need for an external program
like <TT><FONT FACE="Courier">gnuplot</FONT></TT>.
<P>
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