android kotlin - Bitmap blur effect

MainActivity.kt


package com.cfsuman.kotlintutorials

import android.app.Activity
import android.content.Context
import android.graphics.*
import android.os.Bundle
import android.renderscript.*
import android.widget.*
import java.io.IOException


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

        // get the widgets reference from XML layout
        val imageView = findViewById<ImageView>(R.id.imageView)
        val imageView2 = findViewById<ImageView>(R.id.imageView2)
        val textView2 = findViewById<TextView>(R.id.textView2)
        val seekBar = findViewById<SeekBar>(R.id.seekBar)


        val context = this

        // get the bitmap from assets folder
        val bitmap = assetsToBitmap("rose.jpg")
        val duplicate = assetsToBitmap("rose.jpg")


        bitmap?.apply {
            // show original bitmap in first image view
            imageView.setImageBitmap(duplicate)

            // show blurred bitmap on second image view
            val initialBlur = seekBar.progress.toFloat() + 1F
            textView2.text = "Blur (Radius : ${initialBlur}F)"
            imageView2.setImageBitmap(blur(context,initialBlur))

            // blur bitmap on seek bar change
            seekBar.setOnSeekBarChangeListener(
                object:SeekBar.OnSeekBarChangeListener{
                override fun onProgressChanged(
                    seekBar: SeekBar?,
                    progress: Int,
                    fromUser: Boolean
                ) {
                    val radius = progress.toFloat() + 1F
                    imageView2.setImageBitmap(blur(context,radius))
                    textView2.text = "Blur (Radius : ${radius}F)"
                }

                override fun onStartTrackingTouch(seekBar: SeekBar?) {
                }

                override fun onStopTrackingTouch(seekBar: SeekBar?) {
                }
            })
        }
    }
}



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



// extension function to blur a bitmap
fun Bitmap.blur(context:Context, radius:Float = 10F):Bitmap?{
    val bitmap = copy(config,true)

    RenderScript.create(context).apply {
        val input = Allocation.createFromBitmap(this,this@blur)
        val output = Allocation.createFromBitmap(this,this@blur)

        ScriptIntrinsicBlur.create(this,Element.U8_4(this)).apply {
            setInput(input)
            // Set the radius of the Blur. Supported range 0 < radius <= 25
            setRadius(radius)
            forEach(output)

            output.copyTo(bitmap)
            destroy()
        }
    }
    return bitmap
}

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:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/rootLayout"
    android:background="#DCDCDC"
    android:padding="24dp">

    <ImageView
        android:id="@+id/imageView"
        android:layout_width="0dp"
        android:layout_height="225dp"
        android:layout_marginTop="8dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="8dp"
        android:padding="8dp"
        android:text="Original Bitmap"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/imageView" />

    <ImageView
        android:id="@+id/imageView2"
        android:layout_width="0dp"
        android:layout_height="225dp"
        android:layout_marginTop="24dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView" />

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="8dp"
        android:gravity="center_horizontal"
        android:text="Blur"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/imageView2" />

    <SeekBar
        android:id="@+id/seekBar"
        style="@style/Widget.AppCompat.SeekBar.Discrete"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginTop="16dp"
        android:max="24"
        android:progress="12"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView2" />

</androidx.constraintlayout.widget.ConstraintLayout>