@Override
  public void process(Bitmap bitmap) {
    final int w = bitmap.getWidth();
    final int h = bitmap.getHeight();

    final Canvas canvas = new Canvas(bitmap);

    mPaint.setAntiAlias(true);
    mPaint.setColor(TEXT_COLOR);
    mPaint.setFakeBoldText(true);
    mPaint.setTextSize(FONT_SIZE);

    for (int c = 0; c < mCount; c++) {
      final int x = mRandom.nextInt(w);
      final int y = mRandom.nextInt(h);
      canvas.drawText(mWatermarkText, x, y, mPaint);
    }
  }
Adds a watermark at random positions to the bitmap using {@link Canvas}.
samples/showcase/src/main/java/com/facebook/fresco/samples/showcase/postprocessor/WatermarkPostprocessor.java