Various colour related Kotlin functions

ColourUtils.kt

import kotlin.math.max
import kotlin.math.min

/**
 * @returns hue, saturation%, brightness%
 */
fun rgbToHsb(r: Int, g: Int, b: Int): Triple<Float, Float, Float> {
    val rF = r / 255f
    val gF = g / 255f
    val bF = b / 255f

    val cMax = max(max(rF, gF), bF)
    val cMin = min(min(rF, gF), bF)
    val delta = cMax - cMin
    
    val hue = when {
        delta == 0f -> 0f
        cMax == rF -> ((gF - bF) / delta) % 6
        cMax == gF -> ((bF - rF) / delta) + 2
        else -> ((rF - gF) / delta) + 4
    } * 60
    
    val saturation = if (cMax == 0f) {
      0f 
    } else {
      delta / cMax
    }
    
    val brightness = cMax
    
    return Triple(
        if (hue < 0) hue + 360 else hue,
        saturation * 100,
        brightness * 100
    )
}

fun isPrimaryColor(r: Int, g: Int, b: Int, threshold: Int = 30): Boolean {
    val isRed = r > 255 - threshold && g < threshold && b < threshold
    
    val isGreen = r < threshold && g > 255 - threshold && b < threshold
    
    val isBlue = r < threshold && g < threshold && b > 255 - threshold
    
    val isYellow = r > 255 - threshold && g > 255 - threshold && b < threshold
    
    return isRed || isGreen || isBlue || isYellow
}

fun isNeonColor(r: Int, g: Int, b: Int): Boolean {
    val (_, saturation, value) = rgbToHsv(r, g, b)
    
    // Definition of neon colour: over 85% saturation, 80% brightness
    val isHighSaturation = saturation > 85
    val isHighValue = value > 80
    
    return isHighSaturation && isHighValue
}