content: /*
   * Copyright (C) 2017 The Android Open Source Project
   *
   * 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
   */
  package allen.town.podcast.util;
  
  import android.graphics.Bitmap;
  import android.graphics.Bitmap.Config;
  import android.graphics.Canvas;
  import android.graphics.Matrix;
  import android.graphics.Paint;
  import android.graphics.PorterDuff;
  import android.graphics.drawable.BitmapDrawable;
  import android.graphics.drawable.Drawable;
  
  /**
   * Utility class for image analysis and processing.
   *
   * @hide
   */
  public class ImageUtils {
    // Amount (max is 255) that two channels can differ before the color is no longer "gray".
    private static final int TOLERANCE = 20;
    // Alpha amount for which values below are considered transparent.
    private static final int ALPHA_TOLERANCE = 50;
    // Size of the smaller bitmap we're actually going to scan.
    private static final int COMPACT_BITMAP_SIZE = 64; // pixels
    private final Matrix mTempMatrix = new Matrix();
    private int[] mTempBuffer;
    private Bitmap mTempCompactBitmap;
    private Canvas mTempCompactBitmapCanvas;
    private Paint mTempCompactBitmapPaint;
  
    /**
     * Classifies a color as grayscale or not. Grayscale here means "very close to a perfect gray"; if
     * all three channels are approximately equal, this will return true.
     *
     * <p>Note that really transparent colors are always grayscale.
     */
    public static boolean isGrayscale(int color) {
      int alpha = 0xFF & (color >> 24);
      if (alpha < ALPHA_TOLERANCE) {
        return true;
      }
      int r = 0xFF & (color >> 16);
      int g = 0xFF & (color >> 8);
      int b = 0xFF & color;
      return Math.abs(r - g) < TOLERANCE
          && Math.abs(r - b) < TOLERANCE
          && Math.abs(g - b) < TOLERANCE;
    }
  
    /** Convert a drawable to a bitmap, scaled to fit within maxWidth and maxHeight. */
    public static Bitmap buildScaledBitmap(Drawable drawable, int maxWidth, int maxHeight) {
      if (drawable == null) {
        return null;
      }
      int originalWidth = drawable.getIntrinsicWidth();
      int originalHeight = drawable.getIntrinsicHeight();
      if ((originalWidth <= maxWidth)
          && (originalHeight <= maxHeight)
          && (drawable instanceof BitmapDrawable)) {
        return ((BitmapDrawable) drawable).getBitmap();
      }
      if (originalHeight <= 0 || originalWidth <= 0) {
        return null;
      }
      // create a new bitmap, scaling down to fit the max dimensions of
      // a large notification icon if necessary
      float ratio =
          Math.min(
              (float) maxWidth / (float) originalWidth, (float) maxHeight / (float) originalHeight);
      ratio = Math.min(1.0f, ratio);
      int scaledWidth = (int) (ratio * originalWidth);
      int scaledHeight = (int) (ratio * originalHeight);
      Bitmap result = Bitmap.createBitmap(scaledWidth, scaledHeight, Config.ARGB_8888);
      // and paint our app bitmap on it
      Canvas canvas = new Canvas(result);
      drawable.setBounds(0, 0, scaledWidth, scaledHeight);
      drawable.draw(canvas);
      return result;
    }
  
    /**
     * Checks whether a bitmap is grayscale. Grayscale here means "very close to a perfect gray".
     *
     * <p>Instead of scanning every pixel in the bitmap, we first resize the bitmap to no more than
     * COMPACT_BITMAP_SIZE^2 pixels using filtering. The hope is that any non-gray color elements will
     * survive the squeezing process, contaminating the result with color.
     */
    public boolean isGrayscale(Bitmap bitmap) {
      int height = bitmap.getHeight();
      int width = bitmap.getWidth();
  
      // shrink to a more manageable (yet hopefully no more or less colorful) size
      if (height > COMPACT_BITMAP_SIZE || width > COMPACT_BITMAP_SIZE) {
        if (mTempCompactBitmap == null) {
          mTempCompactBitmap =
              Bitmap.createBitmap(COMPACT_BITMAP_SIZE, COMPACT_BITMAP_SIZE, Config.ARGB_8888);
          mTempCompactBitmapCanvas = new Canvas(mTempCompactBitmap);
          mTempCompactBitmapPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
          mTempCompactBitmapPaint.setFilterBitmap(true);
        }
        mTempMatrix.reset();
        mTempMatrix.setScale(
            (float) COMPACT_BITMAP_SIZE / width, (float) COMPACT_BITMAP_SIZE / height, 0, 0);
        mTempCompactBitmapCanvas.drawColor(0, PorterDuff.Mode.SRC); // select all, erase
        mTempCompactBitmapCanvas.drawBitmap(bitmap, mTempMatrix, mTempCompactBitmapPaint);
        bitmap = mTempCompactBitmap;
        width = height = COMPACT_BITMAP_SIZE;
      }
      final int size = height * width;
      ensureBufferSize(size);
      bitmap.getPixels(mTempBuffer, 0, width, 0, 0, width, height);
      for (int i = 0; i < size; i++) {
        if (!isGrayscale(mTempBuffer[i])) {
          return false;
        }
      }
      return true;
    }
  
    /** Makes sure that {@code mTempBuffer} has at least length {@code size}. */
    private void ensureBufferSize(int size) {
      if (mTempBuffer == null || mTempBuffer.length < size) {
        mTempBuffer = new int[size];
      }
    }
  }
  