How to set Alpha for HexColor

alphaHexColor.kt

import kotlin.math.roundToInt

fun main(args: Array<String>) {

    println("#2c79a5".alphaColor(0.5F))
    println(getColorIntWithAlpha("#2c79a5",0.5F))
}

fun getColorIntWithAlpha(hexColor: String, alpha: Float): Int =
        Color.parseColor(hexColor.alphaColor(alpha))

fun String.alphaColor(percentage: Float): String = if (percentage < 0 || percentage > 1) {
    fail("The percentage need to be a float number between 0.0 and 1.0")
} else {
    val alphInt = ((percentage * 255) + 0.000001).roundToInt()
    val alphaHex = String.format("%02X", alphInt)
    this.replace("#", "#$alphaHex")
}


fun fail(message: String): Nothing {
    throw IllegalArgumentException(message)
}