android kotlin - Bitmap change brightness contrast

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 textView = findViewById<TextView>(R.id.textView)
        val seekBarBrightness = findViewById<SeekBar>(R.id.seekBarBrightness)
        val tvBrightness = findViewById<TextView>(R.id.tvBrightness)
        val seekBarContrast = findViewById<SeekBar>(R.id.seekBarContrast)
        val tvContrast = findViewById<TextView>(R.id.tvContrast)


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


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

            // initial bitmap on second image view
            imageView2.setImageBitmap(this)


            // change bitmap brightness on seek bar change
            seekBarBrightness.setOnSeekBarChangeListener(object:
                SeekBar.OnSeekBarChangeListener{
                override fun onProgressChanged(
                    seekBar: SeekBar?,
                    progress: Int,
                    fromUser: Boolean
                ) {
                    val brightness = progress.toFloat()-200
                    val contrast = seekBarContrast.progress.toFloat()/10F

                    imageView2.setImageBitmap(
                        setBrightnessContrast(
                            brightness=brightness,
                            contrast = contrast
                        )
                    )
                    tvBrightness.text = "Brightness $brightness"+"F"
                }
                override fun onStartTrackingTouch(seekBar: SeekBar?) {
                }

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


            // change bitmap contrast on seek bar change
            seekBarContrast.setOnSeekBarChangeListener(object:
                SeekBar.OnSeekBarChangeListener{
                override fun onProgressChanged(
                    seekBar: SeekBar?,
                    progress: Int,
                    fromUser: Boolean
                ) {
                    val brightness = seekBarBrightness.progress.toFloat()-200
                    val contrast = progress.toFloat()/10F

                    imageView2.setImageBitmap(
                        setBrightnessContrast(
                            brightness=brightness,
                            contrast = contrast
                        )
                    )
                    tvContrast.text = "Contrast $contrast"+"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 change bitmap brightness and contrast
fun Bitmap.setBrightnessContrast(
    brightness:Float = 0.0F,
    contrast:Float = 1.0F
):Bitmap?{
    val bitmap = copy(Bitmap.Config.ARGB_8888,true)
    val paint = Paint()


    // brightness -200..200, 0 is default
    // contrast 0..2, 1 is default
    // you may tweak the range
    val matrix = ColorMatrix(
        floatArrayOf(
            contrast, 0f, 0f, 0f, brightness,
            0f, contrast, 0f, 0f, brightness,
            0f, 0f, contrast, 0f, brightness,
            0f, 0f, 0f, 1f, 0f
        )
    )

    val filter = ColorMatrixColorFilter(matrix)
    paint.colorFilter = filter

    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"
    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="210dp"
        android:layout_marginTop="8dp"
        android:scaleType="centerCrop"
        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="210dp"
        android:layout_marginTop="16dp"
        android:scaleType="centerCrop"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView" />

    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginTop="24dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/imageView2">

        <TextView
            android:id="@+id/tvBrightness"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Brightness"
            android:layout_marginStart="16dp"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent" />

        <SeekBar
            android:id="@+id/seekBarBrightness"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginTop="8dp"
            android:max="400"
            android:progress="200"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toBottomOf="@+id/tvBrightness" />

        <TextView
            android:id="@+id/tvContrast"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="8dp"
            android:text="Contrast"
            android:layout_marginStart="16dp"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toBottomOf="@id/seekBarBrightness" />

        <SeekBar
            android:id="@+id/seekBarContrast"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginTop="8dp"
            android:max="20"
            android:progress="10"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toBottomOf="@+id/tvContrast" />

    </androidx.constraintlayout.widget.ConstraintLayout>

</androidx.constraintlayout.widget.ConstraintLayout>