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>