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:

<?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_world" /> <Button android:id="@+id/loadimage" android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="Load Image" /> <TextView android:id="@+id/targeturi" android:layout_width="fill_parent" android:layout_height="wrap_content" /> <ImageView android:id="@+id/targetimage" android:layout_width="fill_parent" android:layout_height="fill_parent" android:scaleType="centerCrop" /> </LinearLayout> 

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