Picasso Grayscale Transformation

GrayscaleTransformation.java

/*
 * Copyright (C) 2014 Square, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import android.graphics.Bitmap;
import android.graphics.BitmapShader;
import android.graphics.Canvas;
import android.graphics.ColorMatrix;
import android.graphics.ColorMatrixColorFilter;
import android.graphics.Paint;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;

import com.batterii.mobile.R;
import com.squareup.picasso.Picasso;
import com.squareup.picasso.Transformation;
import java.io.IOException;

import static android.graphics.Bitmap.createBitmap;
import static android.graphics.Paint.ANTI_ALIAS_FLAG;
import static android.graphics.Shader.TileMode.REPEAT;

public class GrayscaleTransformation implements Transformation {

  private final Picasso picasso;

  public GrayscaleTransformation(Picasso picasso) {
    this.picasso = picasso;
  }

  @Override public Bitmap transform(Bitmap source) {
    Bitmap result = createBitmap(source.getWidth(), source.getHeight(), source.getConfig());
    Bitmap noise;
    try {
      noise = picasso.load(R.drawable.noise).get();
    } catch (IOException e) {
      throw new RuntimeException("Failed to apply transformation! Missing resource.");
    }

    BitmapShader shader = new BitmapShader(noise, REPEAT, REPEAT);

    ColorMatrix colorMatrix = new ColorMatrix();
    colorMatrix.setSaturation(0);
    ColorMatrixColorFilter filter = new ColorMatrixColorFilter(colorMatrix);

    Paint paint = new Paint(ANTI_ALIAS_FLAG);
    paint.setColorFilter(filter);

    Canvas canvas = new Canvas(result);
    canvas.drawBitmap(source, 0, 0, paint);

    paint.setColorFilter(null);
    paint.setShader(shader);
    paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.MULTIPLY));

    canvas.drawRect(0, 0, canvas.getWidth(), canvas.getHeight(), paint);

    source.recycle();
    noise.recycle();

    return result;
  }

  @Override public String key() {
    return "grayscaleTransformation()";
  }
}

noise.png