cmyk

(no submodules)

Purpose

cmyk.ts provides bidirectional conversion between RGB and CMYK colour spaces. CMYK is the subtractive model used in professional printing, where colours are created by mixing cyan, magenta, yellow, and black inks. These conversions are essential for print preview, pre-press workflows, and any application that needs to bridge screen colours with physical output. While RGB is additive (light-emitting), CMYK is subtractive (light-absorbing), making direct translation necessary for accurate colour reproduction across media.

Features

RGB to CMYK conversion with black generation
CMYK to RGB conversion
Percentage-based CMYK output (0–100)
Handles edge cases like pure black and pure white

Usage: Basic Example

import { rgbToCmyk } from "@suaveplan/colour-convert-cmyk";

const cmyk = rgbToCmyk({ r: 128, g: 64, b: 32 });

Usage: Advanced Example

import { rgbToCmyk, cmykToRgb } from "@suaveplan/colour-convert-cmyk";

const ink = rgbToCmyk({ r: 59, g: 130, b: 246 });
const screen = cmykToRgb(ink);

API Reference

`rgbToCmyk(rgb: RGB): CMYK`

Converts an RGB colour to CMYK percentages. The black channel (k) is generated from the maximum of the inverted RGB channels, and the cyan, magenta, and yellow channels are computed relative to this black. This is the standard Euclidean algorithm used in most graphics software.

`cmykToRgb(cmyk: CMYK): RGBA`

Converts CMYK percentages back to RGB. The formula applies the subtractive model in reverse: each RGB channel is the product of (1 - ink) × (1 - black). The alpha channel is always set to 1 because CMYK has no native alpha channel.

Implementation Notes

The conversion uses the standard Euclidean algorithm for RGB to CMYK. When the input colour is pure black (k = 100%), the cyan, magenta, and yellow channels are defined as zero to avoid division by zero. All CMYK values are rounded to the nearest integer percentage. The inverse conversion always produces alpha 1 because CMYK has no native alpha channel. Round-trip conversion may introduce small quantization errors due to the integer rounding of CMYK percentages.

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