Scale bitmap Efficiently

Remark: I have a exercise "Display Gallery selected image using BitmapFactory" before. The original idea is to select image using Android build-in app Gallery, and display on a ImageView, FOR SMALL IMAGE. Recently found that it cannot display large image, such as original photos from camera ~ but I don't know why no error reported!!!

It may be due to the Bitmap is too large for the ImageView. To scale-down the bitmap before display, Android Developer Site have a good article to describe "Loading Large Bitmaps Efficiently".

The old exercise is modified with scale-down bitmap and re-posted here:

Main Code:

package com.example.androidselectimage;

import java.io.FileNotFoundException;

import android.net.Uri;
import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity {
 
 TextView textTargetUri;
 ImageView targetImage;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        Button buttonLoadImage = (Button)findViewById(R.id.loadimage);
        textTargetUri = (TextView)findViewById(R.id.targeturi);
        targetImage = (ImageView)findViewById(R.id.targetimage);
     
        buttonLoadImage.setOnClickListener(new Button.OnClickListener(){
         
         @Override
         public void onClick(View arg0) {
          // TODO Auto-generated method stub
          Intent intent = new Intent(Intent.ACTION_PICK,
            android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
          startActivityForResult(intent, 0);
         }});
        
    }

 @Override
 protected void onActivityResult(int requestCode, int resultCode, Intent data) {
  // TODO Auto-generated method stub
  super.onActivityResult(requestCode, resultCode, data);
  
  if (resultCode == RESULT_OK){
   Uri targetUri = data.getData();
   textTargetUri.setText(targetUri.toString());
   
   Toast.makeText(getApplicationContext(), 
     "ImageView: " + targetImage.getWidth() + " x " + targetImage.getHeight(), 
     Toast.LENGTH_LONG).show();
   
   Bitmap bitmap;
   bitmap = decodeSampledBitmapFromUri(
     targetUri,
     targetImage.getWidth(), targetImage.getHeight());
      
   if(bitmap == null){
    Toast.makeText(getApplicationContext(), "the image data could not be decoded", Toast.LENGTH_LONG).show();
    
   }else{
    Toast.makeText(getApplicationContext(), 
      "Decoded Bitmap: " + bitmap.getWidth() + " x " + bitmap.getHeight(), 
      Toast.LENGTH_LONG).show();
    targetImage.setImageBitmap(bitmap);
   } 
  }
 }
 
 /*
  *  How to "Loading Large Bitmaps Efficiently"?
  *  Refer: http://developer.android.com/training/displaying-bitmaps/load-bitmap.html
  */
 
 public Bitmap decodeSampledBitmapFromUri(Uri uri, int reqWidth, int reqHeight) {

  Bitmap bm = null;
  
  try{
   // First decode with inJustDecodeBounds=true to check dimensions
   final BitmapFactory.Options options = new BitmapFactory.Options();
   options.inJustDecodeBounds = true;
   BitmapFactory.decodeStream(getContentResolver().openInputStream(uri), null, options);

      // Calculate inSampleSize
      options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight);

      // Decode bitmap with inSampleSize set
      options.inJustDecodeBounds = false;
      bm = BitmapFactory.decodeStream(getContentResolver().openInputStream(uri), null, options);
  } catch (FileNotFoundException e) {
   e.printStackTrace();
   Toast.makeText(getApplicationContext(), e.toString(), Toast.LENGTH_LONG).show();
  }
  
     return bm;
 }
    
 public int calculateInSampleSize(
   BitmapFactory.Options options, int reqWidth, int reqHeight) {
  // Raw height and width of image
  final int height = options.outHeight;
  final int width = options.outWidth;
  int inSampleSize = 1;
  
  if (height > reqHeight || width > reqWidth) {
   if (width > height) {
    inSampleSize = Math.round((float)height / (float)reqHeight); 
   } else {
    inSampleSize = Math.round((float)width / (float)reqWidth); 
   } 
  }
  return inSampleSize; 
 }
    
}

Layout:

    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="@string/hello_world" />
    android:id="@+id/loadimage"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="Load Image" />
    android:id="@+id/targeturi"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content" />
    android:id="@+id/targetimage"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:scaleType="centerCrop" />

Download the files.