@spec blend(
  {integer(), integer(), integer()},
  {integer(), integer(), integer()},
  float()
) ::
  {integer(), integer(), integer()}

Blends two RGB colors with a given factor.

Parameters

• color1 - First RGB color tuple
• color2 - Second RGB color tuple
• factor - Blend factor (0.0 = color1, 1.0 = color2)

Returns

• Blended RGB color tuple

Examples

iex> blend({255, 0, 0}, {0, 0, 255}, 0.5)
{128, 0, 128}

@spec clamp(integer()) :: 0..255

Clamps an integer value to the 0-255 range.

Examples

iex> Pote.Conversions.clamp(300)
255

iex> Pote.Conversions.clamp(-10)
0

iex> Pote.Conversions.clamp(128)
128

@spec cmyk_to_rgb(cmyk()) :: rgb()

Converts CMYK to RGB.

Parameters

• cmyk - CMYK tuple {c, m, y, k} where each value is 0-100

Returns

• RGB tuple {r, g, b} where each value is 0-255

Examples

iex> cmyk_to_rgb({0.0, 49.8, 100.0, 0.0})
{255, 128, 0}

@spec color_distance(rgb(), rgb()) :: non_neg_integer()

Calculates Manhattan distance between two RGB colors. Used to find nearest color match.

@spec contrast_ratio(rgb(), rgb()) :: float()

Computes the WCAG 2.1 contrast ratio between two colors.

Parameters

• rgb1 - First RGB color tuple
• rgb2 - Second RGB color tuple

Returns

• Contrast ratio (float). WCAG AA requires 4.5:1 for normal text, 7:1 for AAA.

Examples

iex> contrast_ratio({255, 255, 255}, {0, 0, 0})
21.0

@spec delta_e(rgb(), rgb()) :: float()

Computes the Delta E 1976 distance between two colors.

This is the Euclidean distance in CIELAB space.

Parameters

• rgb1 - First RGB color tuple
• rgb2 - Second RGB color tuple

Returns

• Delta E value (float). Values < 1.0 are imperceptible.

Examples

iex> delta_e({255, 0, 0}, {255, 0, 0})
0.0

@spec hex_to_rgb(hex()) :: {:ok, rgb()} | {:error, :invalid_hex_format}

Converts hexadecimal string to RGB tuple.

Parameters

• hex - Hex string in format "#RRGGBB" or "RRGGBB"

Returns

• {:ok, rgb} - RGB tuple on success
• {:error, reason} - Error tuple if conversion fails

Examples

iex> hex_to_rgb("#FF8000")
{:ok, {255, 128, 0}}

iex> hex_to_rgb("FF8000")
{:ok, {255, 128, 0}}

iex> hex_to_rgb("invalid")
{:error, :invalid_hex_format}

@spec hsl_to_rgb(hsl()) :: rgb()

Converts HSL to RGB.

Parameters

• hsl - HSL tuple {h, s, l} where h is 0-360, s and l are 0-100

Returns

• RGB tuple {r, g, b} where each value is 0-255

Examples

iex> hsl_to_rgb({30.0, 100.0, 50.0})
{255, 128, 0}

@spec hsv_to_rgb(hsv()) :: rgb()

Converts HSV to RGB.

Parameters

• hsv - HSV tuple {h, s, v} where h is 0-360, s and v are 0-100

Returns

• RGB tuple {r, g, b} where each value is 0-255

Examples

iex> hsv_to_rgb({30.0, 100.0, 100.0})
{255, 128, 0}

@spec hwb_to_rgb({number(), number(), number()}) :: rgb()

Converts HWB to RGB.

Parameters

• hwb - HWB tuple {h, w, b} where h is 0-360, w and b are 0.0-1.0

Returns

• RGB tuple {r, g, b} where each value is 0-255

Examples

iex> hwb_to_rgb({0.0, 0.0, 0.0})
{255, 0, 0}

iex> hwb_to_rgb({0.0, 0.5, 0.5})
{128, 64, 64}

@spec kelvin_to_rgb(pos_integer()) :: rgb()

Converts a color temperature in Kelvin to an RGB approximation.

Based on Tanner Helland's algorithm for black-body radiation approximation.

Parameters

• kelvin - Temperature in Kelvin (1000-40000)

Returns

• RGB tuple {r, g, b}

Examples

iex> kelvin_to_rgb(6500)
{255, 249, 253}

@spec lab_to_rgb({float(), float(), float()}) :: rgb()

Converts CIELAB to RGB (sRGB D65).

Parameters

• lab - Lab tuple {l, a, b}

Returns

• RGB tuple {r, g, b} where each value is 0-255

@spec relative_luminance(rgb()) :: float()

Computes the WCAG 2.1 relative luminance of a color.

Parameters

• rgb - RGB tuple {r, g, b} where each value is 0-255

Returns

• Luminance value between 0.0 and 1.0

Examples

iex> relative_luminance({255, 255, 255})
1.0

@spec rgb_to_cmyk(rgb()) :: cmyk()

Converts RGB to CMYK.

Parameters

• rgb - RGB tuple {r, g, b} where each value is 0-255

Returns

• CMYK tuple {c, m, y, k} where each value is 0-100

Examples

iex> rgb_to_cmyk({255, 128, 0})
{0.0, 49.8, 100.0, 0.0}

@spec rgb_to_hex(rgb()) :: hex()

Converts RGB color to hexadecimal string.

Parameters

• rgb - RGB tuple {r, g, b} where each value is 0-255

Returns

• Hex string in format "#RRGGBB"

Examples

iex> rgb_to_hex({255, 128, 0})
"#FF8000"

iex> rgb_to_hex({0, 0, 0})
"#000000"

@spec rgb_to_hsl(rgb()) :: hsl()

Converts RGB to HSL (Hue, Saturation, Lightness).

Parameters

• rgb - RGB tuple {r, g, b} where each value is 0-255

Returns

• HSL tuple {h, s, l} where h is 0-360, s and l are 0-100

Examples

iex> rgb_to_hsl({255, 128, 0})
{30.0, 100.0, 50.0}

@spec rgb_to_hsv(rgb()) :: hsv()

Converts RGB to HSV (Hue, Saturation, Value).

Parameters

• rgb - RGB tuple {r, g, b} where each value is 0-255

Returns

• HSV tuple {h, s, v} where h is 0-360, s and v are 0-100

Examples

iex> rgb_to_hsv({255, 128, 0})
{30.0, 100.0, 100.0}

@spec rgb_to_hwb(rgb()) :: {float(), float(), float()}

Converts RGB to HWB (Hue, Whiteness, Blackness).

Parameters

• rgb - RGB tuple {r, g, b} where each value is 0-255

Returns

• HWB tuple {h, w, b} where h is 0-360, w and b are 0.0-1.0

Examples

iex> rgb_to_hwb({255, 0, 0})
{0.0, 1.0, 0.0}

iex> rgb_to_hwb({128, 128, 128})
{0.0, 0.502, 0.498}

@spec rgb_to_kelvin(rgb()) :: pos_integer() | nil

Approximates the correlated color temperature (CCT) in Kelvin from an RGB color.

Uses an iterative search over the kelvin_to_rgb/1 function to find the closest matching temperature. Returns nil for colors that are not reasonably close to a black-body radiator.

Examples

iex> rgb_to_kelvin({255, 160, 60})
3200

@spec rgb_to_lab(rgb()) :: {float(), float(), float()}

Converts RGB to CIELAB (D65 illuminant).

Parameters

• rgb - RGB tuple {r, g, b} where each value is 0-255

Returns

• Lab tuple {l, a, b} where L is 0-100, a and b are roughly -128 to 127

Examples

iex> rgb_to_lab({255, 128, 0})
{66.89, 37.14, 75.29}

@spec rgb_to_pantone_approx(rgb()) :: {String.t(), float()} | nil

Finds the closest Pantone match for an RGB color.

Uses a curated list of popular Pantone colors and searches for the closest match using Delta E distance in CIELAB space.

Parameters

• rgb - RGB tuple {r, g, b}

Returns

• {pantone_name, distance} tuple, or nil if no close match

Examples

iex> rgb_to_pantone_approx({255, 0, 0})
{"Red 032 C", 0.0}

@spec rgb_to_xterm256(rgb()) :: xterm256()

Converts RGB to XTerm256 color index.

Uses the closest match in the 256-color terminal palette.

Parameters

• rgb - RGB tuple {r, g, b} where each value is 0-255

Returns

• XTerm256 index (0-255)

Examples

iex> rgb_to_xterm256({255, 128, 0})
208

@spec rgb_to_xyz(rgb()) :: {float(), float(), float()}

Converts RGB to CIE XYZ using the sRGB D65 matrix.

Parameters

• rgb - RGB tuple {r, g, b} where each value is 0-255

Returns

• XYZ tuple {x, y, z}

Examples

iex> rgb_to_xyz({255, 128, 0})
{0.487, 0.356, 0.041}

@spec rgb_to_ycbcr(rgb()) :: {integer(), integer(), integer()}

Converts RGB to YCbCr (BT.601, digital video).

Parameters

• rgb - RGB tuple {r, g, b} where each value is 0-255

Returns

• YCbCr tuple {y, cb, cr} where Y is 16-235, Cb/Cr are 16-240

Examples

iex> rgb_to_ycbcr({255, 128, 0})
{165, 69, 224}

@spec rgb_to_yuv(rgb()) :: {integer(), integer(), integer()}

Converts RGB to YUV (BT.601, PAL/NTSC broadcast).

Parameters

• rgb - RGB tuple {r, g, b} where each value is 0-255

Returns

• YUV tuple {y, u, v} where Y is 0-255, U and V are -128 to 127

Examples

iex> rgb_to_yuv({255, 128, 0})
{165, 13, 146}

@spec xterm256_to_rgb(xterm256()) :: rgb()

Converts XTerm256 color index to RGB tuple.

@spec xyz_to_rgb({float(), float(), float()}) :: rgb()

Converts CIE XYZ to RGB (sRGB D65).

Parameters

• xyz - XYZ tuple {x, y, z}

Returns

• RGB tuple {r, g, b} where each value is 0-255

@spec ycbcr_to_rgb({integer(), integer(), integer()}) :: rgb()

Converts YCbCr (BT.601) to RGB.

Parameters

• ycbcr - YCbCr tuple {y, cb, cr}

Returns

• RGB tuple {r, g, b}

@spec yuv_to_rgb({integer(), integer(), integer()}) :: rgb()

Converts YUV (BT.601) to RGB.

Parameters

• yuv - YUV tuple {y, u, v}

Returns

• RGB tuple {r, g, b}