RGB / HSL conversions, dynamic pressed state color

ColorConversions.kt

package eski.utils

import android.graphics.Color
import androidx.annotation.ColorInt
import androidx.core.graphics.blue
import androidx.core.graphics.green
import androidx.core.graphics.red
import com.ministrybrands.genesisapp.models.Config
import kotlin.math.abs
import kotlin.math.max
import kotlin.math.min
import kotlin.math.roundToInt


fun rgbToHsl(red: Int, green: Int, blue: Int): ColorHsl {
  val redNormalized = red / 255f
  val greenNormalized = green / 255f
  val blueNormalized = blue / 255f

  val channelMax = max(max(redNormalized, greenNormalized), blueNormalized)
  val channelMin = min(min(redNormalized, greenNormalized), blueNormalized)
  val channelDelta = channelMax - channelMin

  var hue = when {
    channelDelta == 0f -> 0f
    channelMax == redNormalized -> (((greenNormalized - blueNormalized) / channelDelta) % 6) * 60f
    channelMax == greenNormalized -> ((blueNormalized - redNormalized) / channelDelta + 2) * 60f
    else -> ((redNormalized - greenNormalized) / channelDelta + 4) * 60f
  }

  if (hue < 0) hue += 360f

  val lightnessNormalized = (channelMax + channelMin) / 2f
  val lightness = (lightnessNormalized * 100f).roundToInt()

  val saturationNormalized = if (channelDelta == 0f) 0f else channelDelta / (1f - abs(2f * lightnessNormalized - 1f))
  val saturation = (saturationNormalized * 100f).roundToInt()

  return ColorHsl(hue.roundToInt(), saturation, lightness)
}

fun hslToRgb(hue: Int, saturation: Int, lightness: Int): ColorRgb {
  val hueNormalized = hue / 360f
  val saturationNormalized = saturation / 100f
  val lightnessNormalized = lightness / 100f

  if (saturationNormalized == 0f) {
    val rgb = (lightnessNormalized * 255f).roundToInt()
    return ColorRgb(rgb, rgb, rgb)
  }

  val q = if (lightnessNormalized < 0.5f) {
    lightnessNormalized * (1f + saturationNormalized)
  } else {
    lightnessNormalized + saturationNormalized - (lightnessNormalized * saturationNormalized)
  }

  val p = 2f * lightnessNormalized - q

  val red = hueToRgb(p, q, hueNormalized + 1f / 3f)
  val green = hueToRgb(p, q, hueNormalized)
  val blue = hueToRgb(p, q, hueNormalized - 1f / 3f)

  return ColorRgb((red * 255f).roundToInt(), (green * 255f).roundToInt(), (blue * 255f).roundToInt())
}

private fun hueToRgb(p: Float, q: Float, tParam: Float): Float {
  var t = tParam
  if (t < 0f) t += 1
  if (t > 1f) t -= 1
  if (t < 1f / 6f) return p + (q - p) * 6f * t
  if (t < 1f / 2f) return q
  if (t < 2f / 3f) return p + (q - p) * (2f / 3f - t) * 6f
  return p
}

inline val @receiver:ColorInt Int.pressedColor: Int
get() {
    val backgroundColor = Config.appearance.actionColor
    val backgroundColorHsl = rgbToHsl(backgroundColor.red, backgroundColor.green, backgroundColor.blue)

    val pressedLightness = if (backgroundColorHsl.lightness < 25) {
      backgroundColorHsl.lightness + 15 // Make dark buttons lighter when pressed.
    } else {
      backgroundColorHsl.lightness - 15 // Make light buttons darker when pressed.
    }

    val pressedColorRgb = hslToRgb(backgroundColorHsl.hue, backgroundColorHsl.saturation, pressedLightness)
    return Color.rgb(pressedColorRgb.red, pressedColorRgb.green, pressedColorRgb.blue)
  }