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package Image::Base ; # Documented at the __END__
# $Id: Base.pm,v 1.8 2000/05/25 20:45:54 root Exp $
use strict ;
use vars qw( $VERSION ) ;
$VERSION = '1.07' ;
use Carp qw( croak ) ;
use Symbol () ;
# All the supplied methods are expected to be inherited by subclasses; some
# will be adequate, some will need to be overridden and some *must* be
# overridden.
### Private methods
#
# _get object
# _set object
sub _get { # Object method
my $self = shift ;
# my $class = ref( $self ) || $self ;
$self->{shift()} ;
}
sub _set { # Object method
my $self = shift ;
# my $class = ref( $self ) || $self ;
my $field = shift ;
$self->{$field} = shift ;
}
sub DESTROY {
; # Save's time
}
### Public methods
sub new { croak __PACKAGE__ . "::new() must be overridden" }
sub xy { croak __PACKAGE__ . "::xy() must be overridden" }
sub load { croak __PACKAGE__ . "::load() must be overridden" }
sub save { croak __PACKAGE__ . "::save() must be overridden" }
sub set { croak __PACKAGE__ . "::set() must be overridden" }
sub get { # Object method
my $self = shift ;
# my $class = ref( $self ) || $self ;
my @result ;
push @result, $self->_get( shift() ) while @_ ;
wantarray ? @result : shift @result ;
}
sub new_from_image { # Object method
my $self = shift ; # Must be an image to copy
my $class = ref( $self ) || $self ;
my $newclass = shift ; # Class of target taken from class or object
croak "new_from_image() cannot read $class" unless $self->can( 'xy' ) ;
my( $width, $height ) = $self->get( -width, -height ) ;
# If $newclass was an object reference we inherit its characteristics
# except for width/height and any arguments we've supplied.
my $obj = $newclass->new( @_, -width => $width, -height => $height ) ;
croak "new_from_image() cannot convert to " . ref $obj unless $obj->can( 'xy' ) ;
for( my $x = 0 ; $x < $width ; $x++ ) {
for( my $y = 0 ; $y < $height ; $y++ ) {
$obj->xy( $x, $y, $self->xy( $x, $y ) ) ;
}
}
$obj ;
}
sub line { # Object method
my $self = shift ;
# my $class = ref( $self ) || $self ;
my( $x0, $y0, $x1, $y1, $colour ) = @_ ;
if( $x0 == $x1 ) {
( $y0, $y1 ) = ( $y1, $y0 ) if $y0 > $y1 ;
for( my $y = $y0 ; $y <= $y1 ; $y++ ) {
$self->xy( $x0, $y, $colour ) ;
}
}
else {
# Line algorithm from Computer Graphics Principles and Practice.
( $x0, $y0, $x1, $y1 ) = ( $x1, $y1, $x0, $y0 ) if $x0 > $x1 ;
my $dy = $y1 - $y0 ;
my $dx = $x1 - $x0 ;
my $m = $dx == 0 ? $dy : $dy / $dx ;
my $y = $y0 ;
for( my $x = $x0 ; $x <= $x1 ; $x++ ) {
$self->xy( $x, int $y, $colour ) ;
$y += $m ;
}
}
}
sub ellipse { # Object method
my $self = shift ;
# my $class = ref( $self ) || $self ;
my( $x0, $y0, $x1, $y1, $colour ) = @_ ;
( $x0, $y0, $x1, $y1 ) = ( $x1, $y1, $x0, $y0 ) if $x0 > $x1 ;
my $ox = $x1 > $x0 ? ( ( $x1 - $x0 ) / 2 ) + $x0 :
( ( $x0 - $x1 ) / 2 ) + $x1 ;
my $oy = $y1 > $y0 ? ( ( $y1 - $y0 ) / 2 ) + $y0 :
( ( $y0 - $y1 ) / 2 ) + $y1 ;
my $a = abs( $x1 - $x0 ) / 2 ;
my $b = abs( $y1 - $y0 ) / 2 ;
my $aa = $a ** 2 ;
my $bb = $b ** 2 ;
# Midpoint ellipse algorithm from Computer Graphics Principles and Practice.
my $x = 0 ;
my $y = $b ;
my $d1 = $bb - ( $aa * $b ) + ( $aa / 4 ) ;
$self->_ellipse_point( $ox, $oy, $x, $y, $colour ) ;
while( ( $aa * ( $y - 0.5 ) ) > ( $bb * ( $x + 1 ) ) ) {
if( $d1 < 0 ) {
$d1 += ( $bb * ( ( 2 * $x ) + 3 ) ) ;
++$x ;
}
else {
$d1 += ( ( $bb * ( ( 2 * $x ) + 3 ) ) +
( $aa * ( ( -2 * $y ) + 2 ) ) ) ;
++$x ;
--$y ;
}
$self->_ellipse_point( $ox, $oy, $x, $y, $colour ) ;
}
my $d2 = ( $bb * ( ( $x + 0.5 ) ** 2 ) ) +
( $aa * ( ( $y - 1 ) ** 2 ) ) -
( $aa * $bb ) ;
while( $y > 0 ) {
if( $d2 < 0 ) {
$d2 += ( $bb * ( ( 2 * $x ) + 2 ) ) +
( $aa * ( ( -2 * $y ) + 3 ) ) ;
++$x ;
--$y ;
}
else {
$d2 += ( $aa * ( ( -2 * $y ) + 3 ) ) ;
--$y ;
}
$self->_ellipse_point( $ox, $oy, $x, $y, $colour ) ;
}
}
sub _ellipse_point { # Object method
my $self = shift ;
# my $class = ref( $self ) || $self ;
my( $ox, $oy, $rx, $ry, $colour ) = @_ ;
$self->xy( $ox + $rx, $oy + $ry, $colour ) ;
$self->xy( $ox - $rx, $oy - $ry, $colour ) ;
$self->xy( $ox + $rx, $oy - $ry, $colour ) ;
$self->xy( $ox - $rx, $oy + $ry, $colour ) ;
}
sub rectangle { # Object method
my $self = shift ;
# my $class = ref( $self ) || $self ;
my( $x0, $y0, $x1, $y1, $colour, $fill ) = @_ ;
if( defined $fill and $fill ) {
$self->_filled_rectangle( $x0, $y0, $x1, $y1, $colour ) ;
}
else {
# A rectangle is simply four lines...
$self->line( $x0, $y0, $x1, $y0, $colour ) ;
$self->line( $x1, $y0, $x1, $y1, $colour ) ;
$self->line( $x1, $y1, $x0, $y1, $colour ) ;
$self->line( $x0, $y1, $x0, $y0, $colour ) ;
}
}
sub _filled_rectangle { # Object method
my $self = shift ;
# my $class = ref( $self ) || $self ;
my( $x0, $y0, $x1, $y1, $colour ) = @_ ;
( $y0, $y1 ) = ( $y1, $y0 ) if $y0 > $y1 ;
for( my $y = $y0 ; $y <= $y1 ; $y++ ) {
$self->line( $x0, $y, $x1, $y, $colour ) ;
}
}
1 ;
__END__
=head1 NAME
Image::Base - base class for loading, manipulating and saving images.
=head1 SYNOPSIS
This class should not be used directly. Known inheritors are Image::Xbm and
Image::Xpm.
use Image::Xpm ;
my $i = Image::Xpm->new( -file => 'test.xpm' ) ;
$i->line( 1, 1, 3, 7, 'red' ) ;
$i->ellipse( 3, 3, 6, 7, '#ff00cc' ) ;
$i->rectangle( 4, 2, 9, 8, 'blue' ) ;
If you want to create your own algorithms to manipulate images in terms of
(x,y,colour) then you could extend this class (without changing the file),
like this:
# Filename: mylibrary.pl
package Image::Base ; # Switch to this class to build on it.
sub mytransform {
my $self = shift ;
my $class = ref( $self ) || $self ;
# Perform your transformation here; might be drawing a line or filling
# a rectangle or whatever... getting/setting pixels using $self->xy().
}
package main ; # Switch back to the default package.
Now if you C<require> mylibrary.pl after you've C<use>d Image::Xpm or any
other Image::Base inheriting classes then all these classes will inherit your
C<mytransform()> method.
=head1 DESCRIPTION
=head2 new_from_image()
my $bitmap = Image::Xbm->new( -file => 'bitmap.xbm' ) ;
my $pixmap = $bitmap->new_from_image( 'Image::Xpm', -cpp => 1 ) ;
$pixmap->save( 'pixmap.xpm' ) ;
Note that the above will only work if you've installed Image::Xbm and
Image::Xpm, but will work correctly for any image object that inherits from
Image::Base and respects its API.
You can use this method to transform an image to another image of the same
type but with some different characteristics, e.g.
my $p = Image::Xpm->new( -file => 'test1.xpm' ) ;
my $q = $p->new_from_image( ref $p, -cpp => 2, -file => 'test2.xpm' ) ;
$q->save ;
=head2 line()
$i->line( $x0, $y0, $x1, $y1, $colour ) ;
Draw a line from point ($x0,$y0) to point ($x1,$y1) in colour $colour.
=head2 ellipse()
$i->ellipse( $x0, $y0, $x1, $y1, $colour ) ;
Draw an oval enclosed by the rectangle whose top left is ($x0,$y0) and bottom
right is ($x1,$y1) using a line colour of $colour.
=head2 rectangle()
$i->rectangle( $x0, $y0, $x1, $y1, $colour, $fill ) ;
Draw a rectangle whose top left is ($x0,$y0) and bottom right is ($x1,$y1)
using a line colour of $colour. If C<$fill> is true then the rectangle will be
filled.
=head2 new()
Virtual - must be overridden.
Recommend that it at least supports C<-file> (filename), C<-width> and
C<-height>.
=head2 new_from_serialised()
Not implemented. Recommended for inheritors. Should accept a string serialised
using serialise() and return an object (reference).
=head2 serialise()
Not implemented. Recommended for inheritors. Should return a string
representation (ideally compressed).
=head2 get()
my $width = $i->get( -width ) ;
my( $hotx, $hoty ) = $i->get( -hotx, -hoty ) ;
Get any of the object's attributes. Multiple attributes may be requested in a
single call.
See C<xy> get/set colours of the image itself.
=head2 set()
Virtual - must be overridden.
Set any of the object's attributes. Multiple attributes may be set in a single
call; some attributes are read-only.
See C<xy> get/set colours of the image itself.
=head2 xy()
Virtual - must be overridden. Expected to provide the following functionality:
$i->xy( 4, 11, '#123454' ) ; # Set the colour at point 4,11
my $v = $i->xy( 9, 17 ) ; # Get the colour at point 9,17
Get/set colours using x, y coordinates; coordinates start at 0.
When called to set the colour the value returned is class specific; when
called to get the colour the value returned is the colour name, e.g. 'blue' or
'#f0f0f0', etc, e.g.
$colour = xy( $x, $y ) ; # e.g. #123456
xy( $x, $y, $colour ) ; # Return value is class specific
We don't normally pick up the return value when setting the colour.
=head2 load()
Virtual - must be overridden. Expected to provide the following functionality:
$i->load ;
$i->load( 'test.xpm' ) ;
Load the image whose name is given, or if none is given load the image whose
name is in the C<-file> attribute.
=head2 save()
Virtual - must be overridden. Expected to provide the following functionality:
$i->save ;
$i->save( 'test.xpm' ) ;
Save the image using the name given, or if none is given save the image using
the name in the C<-file> attribute. The image is saved in xpm format.
=head1 CHANGES
2000/05/05
Added some basic drawing methods. Minor documentation changes.
2000/05/04
Created.
=head1 AUTHOR
Mark Summerfield. I can be contacted as <summer@perlpress.com> -
please include the word 'imagebase' in the subject line.
=head1 COPYRIGHT
Copyright (c) Mark Summerfield 2000. All Rights Reserved.
This module may be used/distributed/modified under the LGPL.
=cut