Merge two image, overlap with Alpha.

Last exercise combine two image side-by-side. In this post, the two images overlap with alpha setting.

The layout is same as in last exercise "Combine bitmap side-by-side".

Main code:

package com.test.androidimageprocessing;

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.Bitmap.Config;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;
import com.example.androidimageprocessing.R;

public class MainActivity extends Activity {
 
 Button btnLoadImage1, btnLoadImage2;
 TextView textSource1, textSource2;
 Button btnProcessing;
 ImageView imageResult;
 
 final int RQS_IMAGE1 = 1;
 final int RQS_IMAGE2 = 2;
 
 Uri source1, source2;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  btnLoadImage1 = (Button)findViewById(R.id.loadimage1);
  btnLoadImage2 = (Button)findViewById(R.id.loadimage2);
  textSource1 = (TextView)findViewById(R.id.sourceuri1);
  textSource2 = (TextView)findViewById(R.id.sourceuri2);
  btnProcessing = (Button)findViewById(R.id.processing);
  imageResult = (ImageView)findViewById(R.id.result);
  
  btnLoadImage1.setOnClickListener(new OnClickListener(){

   @Override
   public void onClick(View arg0) {
    Intent intent = new Intent(Intent.ACTION_PICK,
      android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
    startActivityForResult(intent, RQS_IMAGE1);
   }});
  
  btnLoadImage2.setOnClickListener(new OnClickListener(){

   @Override
   public void onClick(View arg0) {
    Intent intent = new Intent(Intent.ACTION_PICK,
      android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
    startActivityForResult(intent, RQS_IMAGE2);
   }});
  
  btnProcessing.setOnClickListener(new OnClickListener(){

   @Override
   public void onClick(View v) {
    
    if(source1 != null && source2 != null){
     Bitmap processedBitmap = ProcessingBitmap();
     if(processedBitmap != null){
      imageResult.setImageBitmap(processedBitmap);
      Toast.makeText(getApplicationContext(), 
        "Done", 
        Toast.LENGTH_LONG).show();
     }else{
      Toast.makeText(getApplicationContext(), 
        "Something wrong in processing!", 
        Toast.LENGTH_LONG).show();
     }
    }else{
     Toast.makeText(getApplicationContext(), 
       "Select both image!", 
       Toast.LENGTH_LONG).show();
    }
    
   }});
 }

 @Override
 protected void onActivityResult(int requestCode, int resultCode, Intent data) {
  super.onActivityResult(requestCode, resultCode, data);
  if(resultCode == RESULT_OK){
   switch (requestCode){
   case RQS_IMAGE1:
    source1 = data.getData();
    textSource1.setText(source1.toString());
    break;
   case RQS_IMAGE2:
    source2 = data.getData();
    textSource2.setText(source2.toString());
    break;
   }
  }
 }

 private Bitmap ProcessingBitmap(){
  Bitmap bm1 = null;
  Bitmap bm2 =  null;
  Bitmap newBitmap = null;
  
  try {
   bm1 = BitmapFactory.decodeStream(
     getContentResolver().openInputStream(source1));
   bm2 = BitmapFactory.decodeStream(
     getContentResolver().openInputStream(source2));
   
   int w;
   if(bm1.getWidth() >= bm2.getWidth()){
    w = bm1.getWidth();
   }else{
    w = bm2.getWidth();
   }
   
   int h;
   if(bm1.getHeight() >= bm2.getHeight()){
    h = bm1.getHeight();
   }else{
    h = bm2.getHeight();
   }
   
   Config config = bm1.getConfig();
   if(config == null){
    config = Bitmap.Config.ARGB_8888;
   }
   
   newBitmap = Bitmap.createBitmap(w, h, config);
   Canvas newCanvas = new Canvas(newBitmap);
   
   newCanvas.drawBitmap(bm1, 0, 0, null);
   
   Paint paint = new Paint();
   paint.setAlpha(128);
   newCanvas.drawBitmap(bm2, 0, 0, paint);
   
  } catch (FileNotFoundException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
  
  return newBitmap;
 }
 
}

Download the files.

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more: Something about processing images in Android