Saturday, June 27, 2020

android kotlin - Draw rectangle on 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)


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


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

            // draw rectangle on bitmap
            // show bitmap with rectangle in second image view
            imageView2.setImageBitmap(drawRectangle())
        }
    }
}



// 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 draw rectangle on bitmap
fun Bitmap.drawRectangle():Bitmap?{
    val bitmap = copy(config,true)
    val canvas = Canvas(bitmap)

    Paint().apply {
        color = Color.parseColor("#A1CAF1")
        isAntiAlias = true

        // draw rectangle on canvas
        canvas.drawRect(
            20f, // left side of the rectangle to be drawn
            20f, // top side
            width/3 - 20f, // right side
            height - 20f, // bottom side
            this
        )
    }

    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="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" />

</androidx.constraintlayout.widget.ConstraintLayout>