An Identicon Drawable for Android, written in Kotlin

IdenticonDrawable.kt

// 
// written by Robert Brandner
// Based on https://github.com/stewartlord/identicon.js
//

import android.graphics.Canvas
import android.graphics.ColorFilter
import android.graphics.Paint
import android.graphics.PixelFormat.TRANSPARENT
import android.graphics.Rect
import android.graphics.drawable.Drawable
import androidx.core.graphics.ColorUtils
import androidx.core.graphics.withScale
import androidx.core.graphics.withTranslation
import java.security.MessageDigest

class IdenticonDrawable(string : String) : Drawable() {

    private val hash = md5Hash(string)
    private val pixels = hash.take(15).toCharArray().map { it.digitToInt(16) % 2 }
    private val rect = Rect(0, 0, 1, 1)

    private val paint = Paint().apply {
        val hue = (hash.takeLast(7).toInt(16).toFloat() / 0xfffffff) * 360f
        val saturation = 0.7f
        val lightness = 0.5f
        this.color = ColorUtils.HSLToColor(floatArrayOf(hue, saturation, lightness))
    }

    override fun draw(canvas: Canvas) {
        // Get the drawable's bounds
        val width: Int = bounds.width()
        val height: Int = bounds.height()

        fun Canvas.drawPixel(x: Int, y: Int, pixel: Int) {
            if (pixel == 0) return
            withTranslation(x.toFloat(), y.toFloat()) {
                drawRect(rect, paint)
            }
        }

        canvas.withScale(width / 5f, height / 5f) {
            for (i in 0..4) {
                drawPixel(2, i, pixels[i])
                drawPixel(1, i, pixels[i+5])
                drawPixel(3, i, pixels[i+5])
                drawPixel(0, i, pixels[i+10])
                drawPixel(4, i, pixels[i+10])
            }
        }

    }

    override fun setAlpha(alpha: Int) {
        //
    }

    override fun setColorFilter(colorFilter: ColorFilter?) {
        //
    }

    @Deprecated("Deprecated in Java")
    override fun getOpacity(): Int = TRANSPARENT

    @OptIn(ExperimentalStdlibApi::class)
    private fun md5Hash(string: String): String =
       MessageDigest.getInstance("MD5")
           .digest(string.toByteArray()).toHexString(HexFormat.Default)
}