NAME¶
Image::Math::Constrain - Scaling math used in image size constraining (such as
thumbnails)
SYNOPSIS¶
use Image::Math::Constrain;
# Create the math object
my $math = Image::Math::Constrain->new(64, 48);
# Get the scaling values for an arbitrary image
my $Image = My::Image->load("myimage.jpg");
my $scaling = $math->constrain($Image->width, $Image->height);
die "Don't need to scale" if $scaling->{scale} == 1;
# Returns the three values as a list when called in array contect
my ($width, $height, $scale) = $math->constrain(800, 600);
# There are lots of different ways to specify the constrain
# Constrain based on width only
$math = Image::Math::Constrain->new(100, 0);
# Constrain based on height only
$math = Image::Math::Constrain->new(0, 100);
# Or you can provide the two values by ARRAY ref
$math = Image::Math::Constrain->new( [ 64, 48 ] );
# Constrain height and width by the same value
$math = Image::Math::Constrain->new(100);
# Various string forms to do the same thing
$math = Image::Math::Constrain->new('constrain(800x600)');
$math = Image::Math::Constrain->new('300x200');
$math = Image::Math::Constrain->new('300w200h');
$math = Image::Math::Constrain->new('100w');
$math = Image::Math::Constrain->new('100h');
# Serialises back to 'constrain(800x600)'.
# You can use this to store the object if you wish.
my $string = $math->as_string;
DESCRIPTION¶
There are a number of different modules and systems that constrain image sizes,
such as thumbnailing. Every one of these independantly implement the same
logic. That is, given a width and/or height constraint, they check to see if
the image is bigger than the constraint, and if so scale the image down
proportionally so that it fits withint the constraints.
Of course, they all do it slightly differnetly, and some do it better than
others.
"Image::Math::Constrain" has been created specifically to implement
this logic once, and implement it properly. Any module or script that does
image size constraining or thumbnailing should probably be using this for its
math.
METHODS¶
new $width, $height¶
-head2 new [ $width, $height ]
new $width_and_height¶
new $string¶
The "new" constructor takes the dimentions to which you wish to
constrain and creates a new math object.
You can feed a number of different height/width pairs to this object, and it
will returns the scaling you will need to do to shrink the image down to the
constraints, and the final width and height of the image after scaling, at
least one of which should match the constraint.
A value of zero is used to indicate that a dimension should not be constrained.
Thus, "->new(400, 0)" would indicate to constrain the width to
400 pixels, but to ignore the height (only changing it to keep the image
proportional).
The constraint dimensions can be provided in a number of different formats. See
the Synopsis for a quick list of these. To stay compatible with automated
constraint generators, you
can provide constrains as zero width and
zero height, and the math object will not attempt to do any scaling, always
returning the input width/height, and a scaling value of 1.
Once created, the object is fully Storable and re-usable and does not store any
state information from a single calculation run.
Returns a new Image::Math::Constrain object, or "undef" if the
constraints have been defined wrongly.
width¶
The "width" method gets the width constraint for the object.
Returns a positive integer, or zero if there is no width constraint.
height¶
The "height" method gets the height constrain for the object.
Returns a positive integer, or zero if there is no height constraint.
as_string¶
The "as_string" method returns the constrain rule as a string in the
format 'constrain(123x123)'. This string form is also supported by the
constructor and so it provides a good way to serialise the constrain rule,
should you ever need to do so.
As this value is not localisable, it should never really be shown to the user
directly, unless you are sure you will never add i18n to your app.
constrain $width, $height¶
The "constrain" method takes the height and width of an image and
applies the constrain math to them to get the final width, height and the
scaling value needed in order to get the your image from it's current size to
the final size.
The resulting size will be in proportion to the original (it will have the same
aspect ratio) and will never be larger than the original.
When called in array context, returns the new dimensions and scaling value as a
list, as in the following.
my ($width, $height, $scale) = $math->constrain(800, 600);
When called in scalar context, it returns a reference to a hash containing the
keys 'width', 'height', and 'scale'.
my $hash = $math->constrain(800, 600);
print "New Width : $hash->{width}\n";
print "New Height : $hash->{height}\n";
print "Scaling By : $hash->{scalar}\n";
Having been created correctly, the object will only return an error if the width
and height arguments are not correct (are not positive integers).
In list context, returns a null list, so all three values will be
"undef".
In scalar context, just returns "undef".
TO DO¶
- Write more special-case unit tests
SUPPORT¶
Bugs should always be submitted via the CPAN bug tracker
<
http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Image-Math-Constrain>
For other issues, contact the maintainer
AUTHORS¶
Adam Kennedy <adamk@cpan.org>
Thank you to Phase N (<
http://phase-n.com/>) for permitting the open
sourcing and release of this distribution.
COPYRIGHT¶
Copyright 2004 - 2008 Adam Kennedy.
This program is free software; you can redistribute it and/or modify it under
the same terms as Perl itself.
The full text of the license can be found in the LICENSE file included with this
module.