android kotlin - Bitmap invert colors

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)

        // get the bitmap from assets
        val bitmap = assetsToBitmap("flower103.jpg")

        bitmap?.apply {
            // set original bitmap to first image view
            imageView.setImageBitmap(this)

            // set inverted colors bitmap to second image view
            invertColors()?.apply {
                imageView2.setImageBitmap(this)
            }
        }
    }
}


// extension function to get a 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 invert bitmap colors
fun Bitmap.invertColors(): Bitmap? {
    val bitmap = Bitmap.createBitmap(
        width,
        height,
        Bitmap.Config.ARGB_8888
    )

    val matrixInvert = ColorMatrix().apply {
        set(
            floatArrayOf(
                -1.0f, 0.0f, 0.0f, 0.0f, 255.0f,
                0.0f, -1.0f, 0.0f, 0.0f, 255.0f,
                0.0f, 0.0f, -1.0f, 0.0f, 255.0f,
                0.0f, 0.0f, 0.0f, 1.0f, 0.0f
            )
        )
    }

    val paint = Paint()
    ColorMatrixColorFilter(matrixInvert).apply {
        paint.colorFilter = this
    }

    Canvas(bitmap).drawBitmap(this, 0f, 0f, paint)
    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"
    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: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:text="Inverted Colors Bitmap"
        app:layout_constraintEnd_toEndOf="@+id/imageView2"
        app:layout_constraintStart_toStartOf="@+id/imageView2"
        app:layout_constraintTop_toBottomOf="@+id/imageView2" />

</androidx.constraintlayout.widget.ConstraintLayout>