colour 0.0.4

converts and manipulates various color representation (HSL, RVB, web, X11, ...)

======
Colour
======

.. image:: https://pypip.in/v/colour/badge.png
:target: https://pypi.python.org/pypi/colour

.. image:: https://secure.travis-ci.org/vaab/colour.png?branch=master
:target: http://travis-ci.org/vaab/colour

Converts and manipulates common color representation (RGB, HSV, web, ...)


Feature
=======

- Damn simple and pythonic way to manipulate color representation (see
examples below)

- Full conversion between RGB, HSV, 6-digit hex, 3-digit hex, human color

- One object (``Color``) or bunch of single purpose function (``rgb2hex``,
``hsl2rgb`` ...)

- ``web`` format that use the smallest representation between 6-digit,
3-digit, fully spelled color, that is compatible with CSS or HTML color
specifications.

- smooth intuitive color scale generation choosing N color gradients.

- can pick colors for you to identify objects of your application.


Installation
============

You don't need to download the GIT version of the code as ``colour`` is
available on the PyPI. So you should be able to run::

pip install colour


Usage
=====

To get complete demo of each function, please read the source code which is
heavily documented and provide a lot of examples in doctest format.

Here is a reduced sample of a common usage scenario:


Instantiation
-------------

Let's create blue color:

>>> from colour import Color
>>> c = Color("blue")
>>> c
<Color blue>

Please note that all these are equivalent examples to create the red color::

Color("red") ## human, web compatible representation
Color(red=1) ## default amount of blue and green is 0.0
Color("blue", hue=0) ## hue of blue is 0.66, hue of red is 0.0
Color("#f00") ## standard 3 hex digit web compatible representation
Color("#ff0000") ## standrad 6 hex digit web compatible representation
Color(hue=0, saturation=1, luminance=0.5)
Color(hsl=(0, 1, 0.5)) ## full 3-uple HSL specification
Color(rgb=(1, 0, 0)) ## full 3-uple RGB specification
Color(Color("red")) ## recursion doesn't break object


Reading values
--------------

Several representation are accessible:

>>> c.hex
'#00f'
>>> c.hsl # doctest: +ELLIPSIS
(0.66..., 1.0, 0.5)
>>> c.rgb
(0.0, 0.0, 1.0)

And their different parts are also independantly accessible, as the different
amount of red, blue, green, of the RGB format:

>>> c.red
0.0
>>> c.blue
1.0
>>> c.green
0.0

Or the hue, saturation and luminance of the HSL representation.

>>> c.hue # doctest: +ELLIPSIS
0.66...
>>> c.saturation
1.0
>>> c.luminance
0.5


Modifying color objects
-----------------------

All these property are read/write, so let's add some red to this color:

>>> c.red = 1
>>> c
<Color magenta>

We might want to de-saturate this color:

>>> c.saturation = 0.5
>>> c
<Color #bf40bf>

And of course, the string convertion will give the web representation which is
human, or 3-digit, or 6-digit hex representation depending which is usable::

>>> "%s" % c
'#bf40bf'

>>> c.luminance = 1
>>> "%s" % c
'white'


Ranges of colors
----------------

You can get some color scale of variation between two ``Color`` objects quite
easily. Here, is the color scale of the rainbow between red and blue:

>>> red = Color("red")
>>> blue = Color("blue")
>>> list(red.range_to(blue, 5))
[<Color red>, <Color yellow>, <Color green>, <Color cyan>, <Color blue>]

Or the different amount of gray between black and white:

>>> black = Color("black")
>>> white = Color("white")
>>> list(black.range_to(white, 6))
[<Color black>, <Color #333>, <Color #666>, <Color #999>, <Color #ccc>, <Color white>]


If you have to create graphical representation with color scale between red and green:

>>> green = Color("green")
>>> list(red.range_to(green, 5))
[<Color red>, <Color #ff7f00>, <Color yellow>, <Color chartreuse>, <Color green>]

Notice how naturally, the yellow is displayed in human format and in the middle
of the scale. And that the quite unusual (but compatible) 'chartreuse' color
specification has been used in place of the hexadecimal representation.


Color comparison
----------------

Sane default
''''''''''''

Color comparison is a vast subject. However, it might seem quite straitforward for
you. ``Colour`` uses a configurable default way of comparing color that might suit
your needs::

>>> Color("red") == Color("#f00") == Color("blue", hue=0)
True

The default comparison algorithm focus only on the "web" representation which is
equivalent to comparing the long hex representation (ie: #FF0000) or to be more
specific, it is equivalent to compare the amount of red, green, and blue composant
of the RGB representation, each of these value being quantized to a 256 value scale.

This default comparison is a practical and convenient way to measure the actual
color equivalence on your screen, or in your video card memory.

But this comparison wouldn't make the difference between a black red, and a
black blue, which both are black::

>>> black_red = Color("red", luminance=0)
>>> black_blue = Color("blue", luminance=0)

>>> black_red == black_blue
True


Customization
'''''''''''''

But, this is not the sole way to compare two colors. As I'm quite lazy, I'm providing
you a way to customize it to your needs. Thus::

>>> from colour import RGB_equivalence, HSL_equivalence
>>> black_red = Color("red", luminance=0, equality=HSL_equivalence)
>>> black_blue = Color("blue", luminance=0, equality=HSL_equivalence)

>>> black_red == black_blue
False

As you might have already guessed, the sane default is ``RGB_equivalence``, so::

>>> black_red = Color("red", luminance=0, equality=RGB_equivalence)
>>> black_blue = Color("blue", luminance=0, equality=RGB_equivalence)

>>> black_red == black_blue
True

Here's how you could implement your unique comparison function::

>>> saturation_equivalence = lambda c1, c2: c1.saturation == c2.saturation
>>> red = Color("red", equality=saturation_equivalence)
>>> blue = Color("blue", equality=saturation_equivalence)
>>> white = Color("white", equality=saturation_equivalence)

>>> red == blue
True
>>> white == red
False

Note: When comparing 2 colors, *only* the equality function *of the first
color will be used*. Thus::

>>> black_red = Color("red", luminance=0, equality=RGB_equivalence)
>>> black_blue = Color("blue", luminance=0, equality=HSL_equivalence)

>>> black_red == black_blue
True

But reverse operation is not equivalent !::

>>> black_blue == black_red
False


Picking arbitrary color for a python object
-------------------------------------------

Basic Usage
'''''''''''

Sometimes, you just want to pick a color for an object in your application
often to visually identify this object. Thus, the picked color should be the
same for same objects, and different for different object.

>>> foo = object()
>>> bar = object()

>>> Color(pick_for=foo) # doctest: +ELLIPSIS
<Color ...>
>>> Color(pick_for=foo) == Color(pick_for=foo)
True
>>> Color(pick_for=foo) == Color(pick_for=bar)
False

Of course, although there's a tiny probability that different strings yield the
same color, most of the time, different inputs will produce different colors.

Advanced Usage
''''''''''''''

You can customize your color picking algorithm by providing a ``picker``. A
``picker`` is a callable that takes an object, and returns something that can
be instanciated as a color by ``Color``.

>>> my_picker = lambda obj: "red" if isinstance(obj, int) else "blue"
>>> Color(pick_for=3, picker=my_picker, pick_key=None)
<Color red>
>>> Color(pick_for="foo", picker=my_picker, pick_key=None)
<Color blue>

You might want to use a particular picker, but enforce how the picker will
identify two object as the same (or not). So there's a ``pick_key`` attribute
that is provided and defaults as equivalent of ``hash`` method and if hash is
not supported by your object, it'll default to the ``str`` of your object salted
with the class name.

Thus:

>>> class MyObj(str): pass
>>> my_obj_color = Color(pick_for=MyObj("foo"))
>>> my_str_color = Color(pick_for="foo")
>>> my_obj_color == my_str_color
False

Please make sure your object is hashable or "stringable" before using the
``RGB_color_picker`` picking mechanism or provide another color picker. Nearly
all python object are hashable by default so this shouldn't be an issue (ie:
instances of ``object`` and subclasses are hashable).

Neither ``hash`` nor ``str`` are perfect solution. So feel free to use
``pick_key`` at ``Color`` instantiation time to set your way to identify
objects, for instance::

>>> a = object()
>>> b = object()
>>> Color(pick_for=a, pick_key=id) == Color(pick_for=b, pick_key=id)
False

When chosing a pick key, you should closely consider if you want your color
to be consistent between runs (this is NOT the case with the last exemple),
or consistent with the content of your object if its a mutable object.

Default value of ``pick_key`` and ``picker`` ensures that the same color will
be attributed to same object between different run on different computer for
most python object.


Color factory
-------------

As you might have noticed, there are few attributes that you might want to see
attached to all of your colors as ``equality`` for equality comparison support,
or ``picker``, ``picker_key`` to configure your object color picker.

You can create a customized ``Color`` factory thanks to the ``make_color_factory``::

>>> from colour import make_color_factory, HSL_equivalence, RGB_color_picker

>>> get_color = make_color_factory(
... equality=HSL_equivalence,
... picker=RGB_color_picker,
... pick_key=str,
... )

All color created thanks to ``CustomColor`` class instead of the default one
would get the specified attributes by default::

>>> black_red = get_color("red", luminance=0)
>>> black_blue = get_color("blue", luminance=0)

Of course, these are always instances of ``Color`` class::

>>> isinstance(black_red, Color)
True

Equality was changed from normal defaults, so::

>>> black_red == black_blue
False

This because the default equivalence of ``Color`` was set to
``HSL_equivalence``.


Changelog
=========

0.0.4 (2013-06-21)
------------------

New
~~~

- Added ``make_color_factory`` to customize some common color
attributes. [Valentin Lab]

- Pick color to identify any python object (fixes #6) [Jonathan Ballet]

- Equality support between colors, customizable if needed. (fixes #3)
[Valentin Lab]

0.0.3 (2013-06-19)
------------------

New
~~~

- Colour is now compatible with python3. [Ryan Leckey]




TODO
====

- ANSI 16-color and 256-color escape sequence generation
- YUV, HSV, CMYK support