Paul Evans > Convert-Color > Convert::Color::HSV

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NAME ^

Convert::Color::HSV - a color value represented as hue/saturation/value

SYNOPSIS ^

Directly:

 use Convert::Color::HSV;

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

 # Can also parse strings
 my $pink = Convert::Color::HSV->new( '0,0.7,1' );

Via Convert::Color:

 use Convert::Color;

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

DESCRIPTION ^

Objects in this class represent a color in HSV 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 value 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 the distance from the axis, and the value 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 circumference of the top of the cylinder contains the pure-saturated color wheel, with a pure white point at its centre.

Because the entire bottom surface of this cylinder contains black, a closely-related color space can be created by reshaping the cylinder into a cone by contracting the base of the cylinder into a point. The radius from the axis is called the chroma (though this is a different definition of "chroma" than that used by CIE).

CONSTRUCTOR ^

$color = Convert::Color::HSV->new( $hue, $saturation, $value )

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 value should be between 0 and 1. Values outside of these ranges will be clamped.

$color = Convert::Color::HSV->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,value

containing the three floating-point values in decimal notation.

METHODS ^

$h = $color->hue

$s = $color->saturation

$v = $color->value

Accessors for the three components of the color.

$c = $color->chroma

Returns the derived property of "chroma", which maps the color space onto a cone 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, $value ) = $color->hsv

Returns the individual hue, saturation and value components of the color value.

$measure = $color->dst_hsv( $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_hsv_cheap( $other )

Returns a measure of the distance between the two colors. This is used in the calculation of dst_hsv 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 ^

AUTHOR ^

Paul Evans <leonerd@leonerd.org.uk>

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