android kotlin - Rotate a bitmap

MainActivity.kt

package com.cfsuman.kotlintutorials

import android.app.Activity
import android.content.Context
import android.graphics.*
import android.os.Bundle
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)


        // get the bitmap from assets folder
        val bitmap = assetsToBitmap("flower2.jpg")


        // If bitmap is not null
        bitmap?.apply {
            // show original bitmap in first image view
            imageView.setImageBitmap(this)

            // initial bitmap on second image view
            imageView2.setImageBitmap(rotate(seekBar.progress.toFloat()))
            textView2.text = "Rotated Bitmap (Degrees ${seekBar.progress})"

            // rotate bitmap on seek bar change
            seekBar.setOnSeekBarChangeListener(
                object: SeekBar.OnSeekBarChangeListener{
                    override fun onProgressChanged(
                        seekBar: SeekBar?,
                        progress: Int,
                        fromUser: Boolean
                    ) {
                        // show rotated bitmap in second image view
                        imageView2.setImageBitmap(rotate(progress.toFloat()))
                        textView2.text = "Rotated Bitmap (Degrees $progress)"
                    }

                    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 rotate bitmap
fun Bitmap.rotate(degrees:Float = 180F):Bitmap?{
    val matrix = Matrix()
    matrix.postRotate(degrees)

    return Bitmap.createBitmap(
        this, // source bitmap
        0, // x coordinate of the first pixel in source
        0, // y coordinate of the first pixel in source
        width, // The number of pixels in each row
        height, // The number of rows
        matrix, // Optional matrix to be applied to the pixels
        false // true if the source should be filtered
    )
}

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="250dp"
        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:text="Original Bitmap"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="@+id/imageView"
        app:layout_constraintTop_toBottomOf="@+id/imageView" />

    <ImageView
        android:id="@+id/imageView2"
        android:layout_width="0dp"
        android:layout_height="250dp"
        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:text="Rotated Bitmap"
        app:layout_constraintEnd_toEndOf="@+id/imageView2"
        app:layout_constraintStart_toStartOf="@+id/imageView2"
        app:layout_constraintTop_toBottomOf="@+id/imageView2" />

    <SeekBar
        android:id="@+id/seekBar"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginTop="8dp"
        android:max="360"
        android:progress="0"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView2" />

</androidx.constraintlayout.widget.ConstraintLayout>