NAME

       "Convert::Color::HSL" - a color value represented as hue/saturation/lightness

SYNOPSIS

       Directly:

        use Convert::Color::HSL;

        my $red = Convert::Color::HSL->new( 0, 1, 0.5 );

        # Can also parse strings
        my $pink = Convert::Color::HSL->new( '0,1,0.8' );

       Via Convert::Color:

        use Convert::Color;

        my $cyan = Convert::Color->new( 'hsl:300,1,0.5' );

DESCRIPTION

       Objects in this class represent a color in HSL space, as a set of three floating-point values. Hue is
       stored as a value in degrees, in the range 0 to 360 (exclusive). Saturation and lightness are in the
       range 0 to 1.

       This color space may be considered as a cylinder, of height and radius 1. Hue represents the position of
       the color as the angle around the axis, the saturation as the distance from the axis, and the lightness
       the height above the base. In this shape, the entire base of the cylinder is pure black, the axis through
       the centre represents the range of greys, and the entire top of the cylinder is pure white. The
       circumference of the circular cross-section midway along the axis contains the pure-saturated color
       wheel.

       Because both surfaces of this cylinder contain pure black or white discs, a closely-related color space
       can be created by reshaping the cylinder into a bi-cone such that the top and bottom of the cylinder
       become single points. The radius from the axis of this shape is called the chroma (though this is a
       different definition of "chroma" than that used by CIE).

       While the components of this space are called Hue-Chroma-Lightness, it should not be confused with the
       similarly-named Hue-Chroma-Luminance (HCL) space.

CONSTRUCTOR

   $color = Convert::Color::HSL->new( $hue, $saturation, $lightness )
       Returns a new object to represent the set of values given. The hue should be in the range 0 to 360
       (exclusive), and saturation and lightness should be between 0 and 1. Values outside of these ranges will
       be clamped.

   $color = Convert::Color::HSL->new( $string )
       Parses $string for values, and construct a new object similar to the above three-argument form. The
       string should be in the form

        hue,saturation,lightnes

       containing the three floating-point values in decimal notation.

METHODS

   $h = $color->hue
   $s = $color->saturation
   $v = $color->lightness
       Accessors for the three components of the color.

   $c = $color->chroma
       Returns the derived property of "chroma", which maps the color space onto a bicone instead of a cylinder.
       This more closely measures the intuitive concept of how "colorful" the color is than the saturation value
       and is useful for distance calculations.

   ( $hue, $saturation, $lightness ) = $color->hsl
       Returns the individual hue, saturation and lightness components of the color value.

   $measure = $color->dst_hsl( $other )
       Returns a measure of the distance between the two colors. This is the Euclidean distance between the two
       colors as points in the chroma-adjusted cone space.

   $measure = $color->dst_hsl_cheap( $other )
       Returns a measure of the distance between the two colors. This is used in the calculation of "dst_hsl"
       but since it omits the final square-root and scaling it is cheaper to calculate, for use in cases where
       only the relative values matter, such as when picking the "best match" out of a set of colors. It ranges
       between 0 for identical colors and 4 for the distance between complementary pure-saturated colors.

SEE ALSO

       •   Convert::Color - color space conversions

       •   Convert::Color::RGB - a color value represented as red/green/blue

       •   <http://en.wikipedia.org/wiki/HSL_and_HSV> - HSL and HSV on Wikipedia

AUTHOR

       Paul Evans <leonerd@leonerd.org.uk>