assign_rgb_color¶

Usage:

 my $rgb = assign_rgb_color($str);

Map a string to an RGB color. This is done by producing SHA-1 digest (160bit, 20 bytes) of the string, then taking the first, 10th, and last byte to become the RGB color.

assign_rgb_dark_color¶

Like "assign_rgb_color" except that it will make sure the assigned color is dark.

assign_rgb_light_color¶

Like "assign_rgb_color" except that it will make sure the assigned color is light.

hsl2hsv¶

Usage:

 my $hsl = hsl2hsv("0 1 0.5"); # => "0 1 1"

Convert HSL to HSV.

hsl2rgb¶

Usage:

 my $rgb = hsl2rgb("0 1 0.5"); # => ff0000

Convert HSL to RGB. HSL should be given in a whitespace-separated H,S,L values e.g. "0 1 0.5". H (hue degree) has a range from 0-360 where 0 is red, 120 is green, 240 is blue and 360 is back to red. S (saturation) has a range from 0-1 where 0 is gray and 1 is fully saturated hue. L (lumination) has a range from 0-1 where 0 is fully black, 0.5 fully saturated, and 1 is fully white. See also "rgb2hsl".

hsv2hsl¶

Usage:

 my $hsl = hsv2hsl("0 1 1"); # => "0 1 0.5"

Convert HSV to HSL.

hsv2rgb¶

Usage:

 my $rgb = hsv2rgb("0 1 1"); # => ff0000

Convert HSV to RGB. HSV should be given in a whitespace-separated H,S,V values e.g. "0 1 1". H (hue degree) has a range from 0-360 where 0 is red, 120 is green, 240 is blue and 360 is back to red. S (saturation) has a range from 0-1 where 0 is gray and 1 is fully saturated hue. V (value) has a range from 0-1 where 0 is black and 1 is white. See also "rgb2hsv".

int2rgb¶

Usage:

 my $rgb = int2rgb(0xffffff); # => ffffff

Convert integer to RGB string.

mix_2_rgb_colors¶

Usage:

 my $mixed_rgb = mix_2_rgb_colors($rgb1, $rgb2, $pct);

Mix 2 RGB colors. $pct is a number between 0 and 1, by default 0.5 (halfway), the closer to 1 the closer the resulting color to $rgb2.

mix_rgb_colors¶

Usage:

 my $mixed_rgb = mix_rgb_colors($color1, $weight1, $color2, $weight2, ...);

Mix several RGB colors.

rand_rgb_color¶

Usage:

 my $rgb = rand_rgb_color([ $low_limit [ , $high_limit ] ]);

Generate a random RGB color. You can specify the limit. Otherwise, they default to the full range (000000 to ffffff).

rand_rgb_colors¶

Usage:

 my @rgbs = rand_rgb_colors([ \%opts ], $num=1);

Produce $num random RGB colors, with some options. It does not (yet) create a palette of optimally distinct colors, but will make reasonable attempt to make the colors different from one another.

Known options:

• light_color

  Boolean, default true. By default, this function will create light RGB colors, assuming the background color is dark, which is often the case in terminal. If this option is set to false, will create dark colors instead, If this option is set to undef, will create both dark and light colors.

• avoid_colors

  Arrayref or hashref. List of colors to be avoided. You can put, for example, colors that you've already assigned/picked for your palette and don't want to use again.

• max_attempts

  Uint, default 1000. Number of attempts to try generating the next random color if the generated color is rejected because it is light/dark, or because it's in "avoid_colors".

  When the number of attempts has been exceeded, the generated color is used anyway.

• hash_prefix

  Whether to add hash prefix to produced color codes ("#123456") or not ("123456").

reverse_rgb_color¶

Usage:

 my $reversed = reverse_rgb_color($rgb);

Reverse $rgb.

rgb2grayscale¶

Usage:

 my $rgb_gs = rgb2grayscale($rgb);

Convert $rgb to grayscale RGB value.

rgb2hsl¶

Usage:

 my $hsl = rgb2hsl($rgb); # example: "0 1 0.5"

Convert RGB (0-255) to HSL. The result is a space-separated H, S, L values.

rgb2hsv¶

Usage:

 my $hsv = rgb2hsv($rgb); # example: "0 1 255"

Convert RGB (0-255) to HSV. The result is a space-separated H, S, V values. See

rgb2int¶

Usage:

 my $int = rgb2int("ffffff"); # => 16777216, which is 0xffffff

Convert RGB string to integer.

rgb2sepia¶

Usage:

 my $rgb_sepia = rgb2sepia($rgb);

Convert $rgb to sepia tone RGB value.

rgb_diff¶

Usage:

 my $dist = rgb_diff($rgb1, $rgb2[ , $algo ])

Calculate difference between two RGB colors, using one of several algorithms.

• euclidean

  The default. It calculates the distance as:

   ( (R1-R2)**2 + (G1-G2)**2 + (B1-B2)**2 )**0.5
      

  which is the same as what "rgb_distance"() would produce.

• approx1

  This algorithm, described in [1] as "a low cost approximation" and "a combination both weighted Euclidean distance functions, where the weight factors depend on how big the 'red' component of the colour is" with "results that are very close to L*u*v" and "a more stable algorithm", uses the following formula:

   ( 2*(R1-R2)**2 + 4*(G1-G2)**2 + 3*(B1-B2)**2 + Rm*((R1-R2)**2 - (B1-B2)**2)/256 )**0.5
      

  where, Rm or "R mean" is (R1+R2)/2.

• approx2

  Like "approx1", but uses this formula:

   ( 2*(R1-R2)**2 + 4*(G1-G2)**2 + 3*(B1-B2)**2 )**0.5  # if Rm < 128
   ( 3*(R1-R2)**2 + 4*(G1-G2)**2 + 2*(B1-B2)**2 )**0.5  # otherwise
      

• hsv_euclidean

  Convert the RGB values to HSV, then calculate the HSV distance. Please see source code for details.

• hsv_hue1

  Like "hsv_euclidean" but puts more emphasis on hue difference. This algorithm is used, for example, by Color::ANSI::Util when mapping RGB 24bit color to the "closest" the ANSI 256-color or 16-color. This algorithm tends to choose the hued colors instead of favoring to fallback on white/gray, which is more preferred.

TODO: redmean low-cost approximation, CMC l:c.

For more about color difference, try reading <https://en.wikipedia.org/wiki/Color_difference>.

[1] https://www.compuphase.com/cmetric.htm

rgb_distance¶

Usage:

 my $dist = rgb_distance($rgb1, $rgb2)

Calculate the euclidean RGB distance, using this formula:

 ( (R1-R2)**2 + (G1-G2)**2 + (B1-B2)**2 )**0.5

For example, the distance between "000000" and "ffffff" is ~441.67, while the distance between "ffff00" and "ffffff" is 255.

rgb_is_dark¶

Usage:

 my $is_dark = rgb_is_dark($rgb)

Return true if $rgb is a "dark" color, which is determined by checking if the RGB distance to "000000" is smaller than to "ffffff".

rgb_is_light¶

Usage:

 my $is_light = rgb_is_light($rgb)

Return true if $rgb is a "light" color, which is determined by checking if the RGB distance to "000000" is larger than to "ffffff".

rgb_luminance¶

Usage:

 my $luminance = rgb_luminance($rgb);

Calculate standard/objective luminance from RGB value using this formula:

 (0.2126*R) + (0.7152*G) + (0.0722*B)

where R, G, and B range from 0 to 1. Return a number from 0 to 1.

tint_rgb_color¶

Usage:

 my $new_rgb = tint_rgb_color($rgb, $tint_rgb, $pct)

Tint $rgb with $tint_rgb. $pct is by default 0.5. It is similar to mixing, but the less luminance the color is the less it is tinted with the tint color. This has the effect of black color still being black instead of becoming tinted.