Adjust saturation of Bitmap with ColorMatrix

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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().

Adjust saturation of Bitmap with ColorMatrix

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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