Perl Graphics Programming

The SWF::Shape Module

The SWF::Shape object holds a data structure that represents a shape as described in Chapter 8. A shape consists of a series of points, a fill style, and a line style. Example 9-2 uses the methods of the Shape object to draw a logarithmic spiral using the Golden Mean (see http://mathworld.wolfram.com/GoldenRatio.html).

The spiral starts at the origin and the pen moves in a counterclockwise direction. The direction of the curve is determined by cycling through the @dx and @dy arrays; the first segment should be drawn in the positive x and y directions, the second in the positive x, negative y directions, etc. The control points are always on the outside edges of the curve. The result is pictured in Figure 9-3.

Figure 9-3. A logarithmic spiral shape

Example 9-2. A program for drawing a logarithmic spiral shape

#!/usr/bin/perl -w # # Example 9-2. An example using SWF::Shape( ) use strict; use SWF::Shape; SWF::setScale(1.0); my $s = new SWF::Shape( ); # Create a new Shape object $s->setLineStyle(1, 255, 0, 0); my @dx = (1, 1, −1, −1); my @dy = (1, −1, −1, 1); my ($x, $y) = (0, 0); my ($x1, $y1) = (0, 0); my $w = 100; my ($cx, $cy); $s->movePenTo($x, $y); for(my $i=0; $i <= 10; $i++) { $x1 = $x1 + $dx[$i%4] * $w; $y1 = $y1 + $dy[$i%4] * $w; if ($i % 2) { # An odd turn ($cx, $cy) = ($x1, $y); } else { # An even turn ($cx, $cy) = ($x, $y1); } $s->drawCurveTo($cx, $cy, $x1, ...