Scale color and alpha of colormatrix with setScale()

Example of using ColorMatrix.setScale(float rScale, float gScale, float bScale, float aScale).

package com.example.androiddrawbitmap;

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.graphics.Canvas;
import android.graphics.ColorMatrix;
import android.graphics.ColorMatrixColorFilter;
import android.graphics.Paint;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.SeekBar;
import android.widget.SeekBar.OnSeekBarChangeListener;
import android.widget.TextView;

public class MainActivity extends Activity {

 Button btnLoadImage;
 ImageView imageResult;
 SeekBar scaleBarRed, scaleBarGreen, scaleBarBlue, scaleBarAlpha;
 TextView cmScaleText;

 final int RQS_IMAGE1 = 1;

 Uri source;
 Bitmap bitmapMaster;
 Canvas canvasMaster;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);

  btnLoadImage = (Button) findViewById(R.id.loadimage);
  imageResult = (ImageView) findViewById(R.id.result);

  btnLoadImage.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);
   }
  });

  cmScaleText = (TextView) findViewById(R.id.textCMScale);
  scaleBarRed = (SeekBar) findViewById(R.id.scalebarred);
  scaleBarGreen = (SeekBar) findViewById(R.id.scalebargreen);
  scaleBarBlue = (SeekBar) findViewById(R.id.scalebarblue);
  scaleBarAlpha = (SeekBar) findViewById(R.id.scalebaralpha);
  scaleBarRed.setOnSeekBarChangeListener(seekBarChangeListener);
  scaleBarGreen.setOnSeekBarChangeListener(seekBarChangeListener);
  scaleBarBlue.setOnSeekBarChangeListener(seekBarChangeListener);
  scaleBarAlpha.setOnSeekBarChangeListener(seekBarChangeListener);

 }

 @Override
 protected void onActivityResult(int requestCode, int resultCode, Intent data) {
  super.onActivityResult(requestCode, resultCode, data);

  if (resultCode == RESULT_OK) {
   switch (requestCode) {
   case RQS_IMAGE1:
    source = data.getData();

    try {
     bitmapMaster = BitmapFactory
       .decodeStream(getContentResolver().openInputStream(
         source));

     scaleBarRed.setProgress(100);
     scaleBarGreen.setProgress(100);
     scaleBarBlue.setProgress(100);
     scaleBarAlpha.setProgress(100);

     loadBitmapScaleColor();

    } catch (FileNotFoundException e) {
     // TODO Auto-generated catch block
     e.printStackTrace();
    }

    break;
   }
  }
 }

 OnSeekBarChangeListener seekBarChangeListener = 
   new OnSeekBarChangeListener() {

  @Override
  public void onProgressChanged(SeekBar seekBar, int progress,
    boolean fromUser) {
   // TODO Auto-generated method stub

  }

  @Override
  public void onStartTrackingTouch(SeekBar seekBar) {
   // TODO Auto-generated method stub

  }

  @Override
  public void onStopTrackingTouch(SeekBar seekBar) {
   loadBitmapScaleColor();
  }
 };

 private void loadBitmapScaleColor() {
  if (bitmapMaster != null) {

   int progressScaleRed = scaleBarRed.getProgress();
   int progressScaleGreen = scaleBarGreen.getProgress();
   int progressScaleBlue = scaleBarBlue.getProgress();
   int progressScaleAlpha = scaleBarAlpha.getProgress();

   float scaleRed = (float) progressScaleRed/100;
   float scaleGreen = (float) progressScaleGreen/100;
   float scaleBlue = (float) progressScaleBlue/100;
   float scaleAlpha = (float) progressScaleAlpha/100;
   
   cmScaleText.setText("setScale: "
     + String.valueOf(scaleRed) + ", "
     + String.valueOf(scaleGreen) + ", "
     + String.valueOf(scaleBlue) + ", "
     + String.valueOf(scaleAlpha));
   
   Bitmap bitmapColorScaled = updateScale(
     bitmapMaster, 
     scaleRed, 
     scaleGreen, 
     scaleBlue, 
     scaleAlpha);
   
   imageResult.setImageBitmap(bitmapColorScaled);
  }
 }

 private Bitmap updateScale(Bitmap src, float rScale, float gScale, 
   float bScale, float aScale) {

  int w = src.getWidth();
  int h = src.getHeight();

  Bitmap bitmapResult = Bitmap
    .createBitmap(w, h, Bitmap.Config.ARGB_8888);
  Canvas canvasResult = new Canvas(bitmapResult);
  Paint paint = new Paint();
  ColorMatrix colorMatrix = new ColorMatrix();
  colorMatrix.setScale(rScale, gScale, bScale, aScale);
  ColorMatrixColorFilter filter = new ColorMatrixColorFilter(colorMatrix);
  paint.setColorFilter(filter);
  canvasResult.drawBitmap(src, 0, 0, paint);

  return bitmapResult;
 }
}

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:autoLink="web"
        android:text="http://android-er.blogspot.com/"
        android:textStyle="bold" />

    <Button
        android:id="@+id/loadimage"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Load Image 1" />

    <ScrollView
        android:layout_width="match_parent"
        android:layout_height="match_parent" >

        <LinearLayout
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:orientation="vertical" >

            <ImageView
                android:id="@+id/result"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:adjustViewBounds="true"
                android:background="@drawable/ic_launcher"
                android:scaleType="centerInside" />

            <TextView
                android:id="@+id/textCMScale"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:text="ColorMatrix Scale" />

            <SeekBar
                android:id="@+id/scalebarred"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:max="200"
                android:progress="100" />
            <SeekBar
                android:id="@+id/scalebargreen"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:max="200"
                android:progress="100" />
            <SeekBar
                android:id="@+id/scalebarblue"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:max="200"
                android:progress="100" />
            <SeekBar
                android:id="@+id/scalebaralpha"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:max="200"
                android:progress="100" />
        </LinearLayout>
    </ScrollView>

</LinearLayout>

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