Usage ===== To get complete demo of each function, please read the source code (or equivalently :doc:`api`) 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: .. code-block:: pycon >>> from colour import Color >>> c = Color("blue") >>> c Please note that all of these are equivalent examples to create the red color: .. code-block:: python 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") ## standard 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 representations are accessible: .. code-block:: pycon >>> 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 independently accessible, as the different amount of red, blue, green, in the RGB format: .. code-block:: pycon >>> c.red 0.0 >>> c.blue 1.0 >>> c.green 0.0 Or the hue, saturation and luminance of the HSL representation: .. code-block:: pycon >>> c.hue # doctest: +ELLIPSIS 0.66... >>> c.saturation 1.0 >>> c.luminance 0.5 A note on the ``.hex`` property, it'll return the smallest valid value when possible. If you are only interested by the long value, use ``.hex_l``: .. code-block:: pycon >>> c.hex_l '#0000ff' Modifying color objects ----------------------- All of these properties are read/write, so let's add some red to this color: .. code-block:: pycon >>> c.red = 1 >>> c We might want to de-saturate this color: .. code-block:: pycon >>> c.saturation = 0.5 >>> c And of course, the string conversion will give the web representation which is human, or 3-digit, or 6-digit hex representation depending which is usable: .. code-block:: pycon >>> "%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: .. code-block:: pycon >>> red = Color("red") >>> blue = Color("blue") >>> list(red.range_to(blue, 5)) [, , , , ] Or the different amount of gray between black and white: .. code-block:: pycon >>> black = Color("black") >>> white = Color("white") >>> list(black.range_to(white, 6)) [, , , , , ] If you have to create graphical representation with color scale between red and green ('lime' color is full green): .. code-block:: pycon >>> lime = Color("lime") >>> list(red.range_to(lime, 5)) [, , , , ] 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 straightforward for you. ``Colour`` uses a configurable default way of comparing color that might suit your needs: .. code-block:: pycon >>> Color("red") == Color("#f00") == Color("blue", hue=0) True The default comparison algorithm focuses only on the "web" representation which is equivalent to comparing the long hex representation (e.g. #FF0000) or to be more specific, it is equivalent to compare the amount of red, green, and blue composition 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: .. code-block:: pycon >>> 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: .. code-block:: pycon >>> from colour import RGB_equivalence, HSL_equivalence >>> Color.equality = staticmethod(HSL_equivalence) >>> black_red = Color("red", luminance=0) >>> black_blue = Color("blue", luminance=0) >>> black_red == black_blue False You may also set it per instance: .. code-block:: pycon >>> 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: .. code-block:: pycon >>> Color.equality = staticmethod(RGB_equivalence) >>> black_red = Color("red", luminance=0) >>> black_blue = Color("blue", luminance=0) >>> black_red == black_blue True Here's how you could implement your unique comparison function: .. code-block:: pycon >>> 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 with equality set per instance, *only* the equality function *of the first color will be used*. Thus: .. code-block:: pycon >>> 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 !: .. code-block:: pycon >>> black_blue == black_red False Equality to non-Colour objects ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ As a side note, whatever your custom equality function is, it won't be used if you compare to anything else than a ``Colour`` instance: .. code-block:: pycon >>> red = Color("red", equality=lambda c1, c2: True) >>> blue = Color("blue", equality=lambda c1, c2: True) Note that these instances would compare as equal to any other color: .. code-block:: pycon >>> red == blue True But on another non-Colour object: .. code-block:: pycon >>> red == None False >>> red != None True Actually, ``Colour`` instances will, politely enough, leave the other side of the equality have a chance to decide of the output, (by executing its own ``__eq__``), so: .. code-block:: pycon >>> class OtherColorImplem(object): ... def __init__(self, color): ... self.color = color ... def __eq__(self, other): ... return self.color == other.web ... >>> alien_red = OtherColorImplem("red") >>> red == alien_red True >>> blue == alien_red False And inequality (using ``__ne__``) are also polite: .. code-block:: pycon >>> class AnotherColorImplem(OtherColorImplem): ... def __ne__(self, other): ... return self.color != other.web ... >>> new_alien_red = AnotherColorImplem("red") >>> red != new_alien_red False >>> blue != new_alien_red True 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: .. code-block:: pycon >>> foo = object() >>> bar = object() >>> Color(pick_for=foo) # doctest: +ELLIPSIS >>> 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 instantiated as a color by ``Color``: .. code-block:: pycon >>> my_picker = lambda obj: "red" if isinstance(obj, int) else "blue" >>> Color(pick_for=3, picker=my_picker, pick_key=None) >>> Color(pick_for="foo", picker=my_picker, pick_key=None) 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: .. code-block:: pycon >>> 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 (e.g. 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: .. code-block:: pycon >>> a = object() >>> b = object() >>> Color(pick_for=a, pick_key=id) == Color(pick_for=b, pick_key=id) False When choosing 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 example), or consistent with the content of your object if it is 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``, ``pick_key`` to configure your object color picker. You can create a customized ``Color`` factory thanks to the ``make_color_factory``: .. code-block:: pycon >>> 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: .. code-block:: pycon >>> black_red = get_color("red", luminance=0) >>> black_blue = get_color("blue", luminance=0) Of course, these are always instances of ``Color`` class: .. code-block:: pycon >>> isinstance(black_red, Color) True Equality was changed from normal defaults, so: .. code-block:: pycon >>> black_red == black_blue False This because the default equivalence of ``Color`` was set to ``HSL_equivalence``.