Andy Wardley > Template-Plugin-Colour-0.01 > Template::Plugin::Colo(u)r

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Source   Latest Release: Template-Plugin-Colour-0.05

NAME ^

Template::Plugin::Colo(u)r - Template plugin for colour manipulation

SYNOPSIS ^

    # long or short hex triplets, with or without '#'
    [% USE Colour('abc')     %]    
    [% USE Colour('#abc')    %]   
    [% USE Colour('ff0000')  %] 
    [% USE Colour('#ff0000') %]

    # decimal r, g, b values
    [% USE Colour(255, 128, 0) %]

    # named parameters
    [% USE Colour( red=255, green=128, blue=0 ) %]

    # explicit colour space
    [% USE Colour( rgb = [255, 128, 10] ) %] 
    [% USE Colour( hsv = [120, 180, 20] ) %] 

    # alternately, call Colour methods
    [% USE Colour;

       # create RGB colours
       red    = Colour.RGB('#c00');
       green  = Colour.RGB('#0c0');
       blue   = Colour.RGB('#00c');

       # create HSV colours
       orange = Colour.HSV(30, 255, 255);
    %]

DESCRIPTION ^

This Template Toolkit plugin module allows you to define and manipulate colours using the RGB (red, green, blue) and HSV (hue, saturation, value) colour spaces.

It delegates to the Template::Plugin::Colour::RGB and Template::Plugin::Colour::HSV modules to do all the hard work.

As a convenience to our American friends and other international users who spell 'Colour' as 'Color', all the 'Colour' plugin modules have 'Color' equivalents. So you can write either:

    [% USE Colour %]

or:

    [% USE Color %]

The same is true of the other plugins as well (Color.RGB, Color.HSV).

METHODS ^

new(@args)

Creates a new colour object. The first argument can denote the intended colour space: 'rgb' or 'hsv' (either upper or lower case is accepted).

    [% USE Colour( rgb = [100, 150, 200] ) %]
    [% USE Colour( hsv = [120, 140, 160] ) %]

If the colour space argument isn't specified then it defaults to RGB.

    [% USE Colour( 100, 150, 200 ) %]   # RGB colour

The new() method delegates to RGB() or HSV() depending on the colour space.

RGB(@args)

Create a new colour object using the RGB colour space. See Template::Plugin::Colour::RGB.

HSV(@args)

Create a new colour object using the HSV colour space. See Template::Plugin::Colour::HSV.

COLOUR SPACE CONVERSION ALGORITHMS ^

The algorithms used to covert between the RGB and HSV colour spaces are based on the the C Code in "Computer Graphics -- Principles and Practice,", Foley et al, 1996, p. 592-593.

Due to a limitation in the particular implementation chosen (to use integers rather than floating point numbers to represent RGB and HSV components), the conversion between colour spaces is not totally symmetrical. That is, if you convert a colour from RGB to HSV and then back again, you may not get back exactly the same colour you started with.

EXAMPLES ^

What Colour is Orange?

Everyone needs to know what colour orange is in RGB and HSV.

I find the easiest way to remember is that its Hue is 30 degrees, with full Saturation and Value.

    [% USE Colour;
       orange = Colour.HSV(30, 255, 255);
    %]

Use the 'rgb' method to convert it to RGB, and 'html' to display it as an HTML formatted hex string.

    <p style="color: [% orange.rgb.html %]">
       I like orange!
    </p>

As it happens, orange is pretty easy to remember in RGB, too. It's #ff7f00 which is full red (ff), half green (7f) and no blue (00). It just goes to reinforce the widely held belief that orange really is one of the best colours ever. Whoever invented it should probably get an award of some kind, or maybe even a pony.

How Do I Make a Nice Colour Scheme?

Let's start with orange, shall we?

    [% USE Colour;
       orange = Colour.HSV(30, 255, 255)
    %]

Now copy it twice to create a lighter (more white) version by reducing the saturation, and a darker version (more black) by reducing the value.

    [% lighter = orange.copy( saturation = 127 );
       darker  = orange.copy( value = 127 );
    %]

Now you can convert them to RGB for display in your HTML page.

    [% orange.html  %]  => #ff7f00
    [% lighter.html %]  => #ffbf80 
    [% darker.html  %]  => #7f3f00

If you want a strongly contrasting colour, then shift the hue 180 degrees around the colour wheel. In this case, going from 30 to 210 to give a nice shade of blue.

    [% contrast = orange.copy( hue = 210 ).html %]  => #007fff

How Much More Black Could This Be?

How much more black could this be?

    [% black = Colour.RGB %]        # defaults to 0, 0, 0

The answer is none. None more black.

AUTHOR ^

Andy Wardley <abw@cpan.org> using algorithms from "Computer Graphics -- Principles and Practice", Foley et al, 1996, p. 592-593.

VERSION ^

This is version 0.01 of the Template::Plugin::Colour module set.

COPYRIGHT ^

Copyright (C) 2006 Andy Wardley. All Rights Reserved.

This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

SEE ALSO ^

Template::Plugin::Colour::RGB, Template::Plugin::Colour::HSV, Template::Plugin

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