Adjust saturation of Bitmap with ColorMatrix

android.graphics.ColorMatrix is a 5x4 matrix for transforming the color+alpha components of a Bitmap. The setSaturation(float sat) method of ColorMatrix set the matrix to affect the saturation of colors. A value of 0 maps the color to gray-scale. 1 is identity.

This example demonstrate how to generate a bitmap with adjusted saturation using ColorMatrix.setSaturation().

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;
 TextView textSource;
 ImageView imageResult;
 SeekBar satBar;
 TextView satText;

 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);
  textSource = (TextView) findViewById(R.id.sourceuri);
  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);
   }
  });

  satText = (TextView) findViewById(R.id.textsat);
  satBar = (SeekBar) findViewById(R.id.satbar);
  satBar.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));

     satBar.setProgress(256);

     loadBitmapSat();

    } 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) {
   loadBitmapSat();
  }
 };

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

   int progressSat = satBar.getProgress();

   //Saturation, 0=gray-scale. 1=identity
   float sat = (float) progressSat / 256;
   satText.setText("Saturation: " + String.valueOf(sat));
   imageResult.setImageBitmap(updateSat(bitmapMaster, sat));
  }
 }

 private Bitmap updateSat(Bitmap src, float settingSat) {

  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.setSaturation(settingSat);
  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" />

    <TextView
        android:id="@+id/sourceuri"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />
    
    <ImageView
        android:id="@+id/result"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:adjustViewBounds="true"
        android:background="@android:color/background_dark"
        android:scaleType="centerInside" />
    
    <TextView 
        android:id="@+id/textsat"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Saturation" />
    <SeekBar
        android:id="@+id/satbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:max="512"
        android:progress="256"/>

</LinearLayout>

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more: Something about processing images in Android