android kotlin - Circular ImageView with border

MainActivity.kt


package com.example.jetpack

import android.content.Context
import android.graphics.*
import android.os.Bundle
import android.util.TypedValue
import androidx.appcompat.app.AppCompatActivity
import androidx.core.graphics.drawable.RoundedBitmapDrawable
import androidx.core.graphics.drawable.RoundedBitmapDrawableFactory
import kotlinx.android.synthetic.main.activity_main.*
import java.io.IOException
import kotlin.math.min


class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        // get bitmap from assets folder
        val bitmap: Bitmap? = assetsToBitmap("flower10.jpg")

        // show the bitmap on first image view
        bitmap?.apply { imageView.setImageBitmap(this) }

        // make the bitmap circular with specified border
        bitmap?.circularWithBorder(
            context = applicationContext,
            borderWidth = 7.dpToPixels(applicationContext),
            borderColor = Color.parseColor("#004225")
        )?.apply {
            imageView2.setImageDrawable(this)
        }
    }
}


// extension function to make a bitmap circular with border
fun Bitmap.circularWithBorder(
    context: Context,
    borderWidth: Float = 25F,
    borderColor: Int = Color.BLACK
): RoundedBitmapDrawable? {
    // calculate the bitmap diameter and radius
    val diameter = (min(width, height) + borderWidth * 2).toInt()
    val radius = diameter / 2F

    val bitmap = Bitmap.createBitmap(diameter, diameter, Bitmap.Config.ARGB_8888)
    val canvas = Canvas(bitmap)
    canvas.drawColor(Color.WHITE)

    // draw bitmap at canvas center
    canvas.drawBitmap(
        this, // bitmap
        (diameter - this.width)/2F, // left
        (diameter - this.height)/2F, // top
        null // paint
    )

    // pa to draw circular border
    Paint().apply {
        style = Paint.Style.STROKE
        // stroke is always centered so double it
        strokeWidth = borderWidth * 2F
        color = borderColor
        isAntiAlias = true

        // draw circular border on canvas
        canvas.drawCircle(canvas.width / 2F,canvas.width / 2F,radius,this)
    }

    // return circular bitmap drawable with border
    return RoundedBitmapDrawableFactory.create(context.resources, bitmap).apply {
        isCircular = true
        setAntiAlias(true)
    }
}


// extension function to convert dp to equivalent pixels
fun Int.dpToPixels(context: Context):Float = TypedValue.applyDimension(
    TypedValue.COMPLEX_UNIT_DIP, this.toFloat(), context.resources.displayMetrics
)


// extension function to get bitmap from assets
fun Context.assetsToBitmap(fileName: String): Bitmap?{
    return try {
        with(assets.open(fileName)){
            BitmapFactory.decodeStream(this)
        }
    } catch (e: IOException) { null }
}

activity_main.xml


<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/constraintLayout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#EDEAE0"
    tools:context=".MainActivity">

    <ImageView
        android:id="@+id/imageView"
        android:layout_width="0dp"
        android:layout_height="280dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:layout_marginEnd="8dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        tools:srcCompat="@tools:sample/avatars" />

    <ImageView
        android:id="@+id/imageView2"
        android:layout_width="0dp"
        android:layout_height="280dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="16dp"
        android:layout_marginEnd="8dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/imageView"
        tools:srcCompat="@tools:sample/avatars" />

</androidx.constraintlayout.widget.ConstraintLayout>