Reduce Bitmap size using BitmapFactory.Options.inSampleSize

The ImageView is loaded with bitmap in full-size. It cost too much resources for a mobile device, and easy to make the app closed unexpectly.

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:orientation="vertical"

    android:layout_width="fill_parent"

    android:layout_height="fill_parent"

    >

<TextView 

    android:layout_width="fill_parent"

    android:layout_height="wrap_content"

    android:text="@string/hello"

    />

<ImageView 

 android:id="@+id/image"

    android:layout_width="fill_parent"

    android:layout_height="wrap_content"

    />

</LinearLayout>




android.graphics.BitmapFactory class provide a method decodeFile(String pathName) to decode a file path into a bitmap. The decoded bitmap can be loaded to ImageView using setImageBitmap() method of the ImageView.




import android.app.Activity;

import android.graphics.Bitmap;

import android.graphics.BitmapFactory;

import android.os.Bundle;

import android.widget.ImageView;

public class AndroidLoadImageViewActivity extends Activity {

  

 String imagefile ="/sdcard/IMG_1.JPG";

  

    /** Called when the activity is first created. */

    @Override

    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.main);

         

        ImageView image = (ImageView)findViewById(R.id.image);

        Bitmap bm = BitmapFactory.decodeFile(imagefile);

        image.setImageBitmap(bm);

    }

}

We can generate a shrinked bitmap using BitmapFactory.Optionswith inSampleSize; such that to reduce the needed resources greatly.

package com.AndroidLoadImageView;

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.widget.ImageView;

public class AndroidLoadImageViewActivity extends Activity {
 
 String imagefile ="/sdcard/IMG_1.JPG";
 
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        ImageView image = (ImageView)findViewById(R.id.image);
        //Bitmap bm = BitmapFactory.decodeFile(imagefile);
        Bitmap bm = ShrinkBitmap(imagefile, 300, 300);
        image.setImageBitmap(bm);
    }
    
 Bitmap ShrinkBitmap(String file, int width, int height){
  
     BitmapFactory.Options bmpFactoryOptions = new BitmapFactory.Options();
        bmpFactoryOptions.inJustDecodeBounds = true;
        Bitmap bitmap = BitmapFactory.decodeFile(file, bmpFactoryOptions);
        
        int heightRatio = (int)Math.ceil(bmpFactoryOptions.outHeight/(float)height);
        int widthRatio = (int)Math.ceil(bmpFactoryOptions.outWidth/(float)width);
        
        if (heightRatio > 1 || widthRatio > 1)
        {
         if (heightRatio > widthRatio)
         {
          bmpFactoryOptions.inSampleSize = heightRatio;
         } else {
          bmpFactoryOptions.inSampleSize = widthRatio; 
         }
        }
        
        bmpFactoryOptions.inJustDecodeBounds = false;
        bitmap = BitmapFactory.decodeFile(file, bmpFactoryOptions);
     return bitmap;
    }
}