content: /*
   * Copyright (C) 2014 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 com.android.internal.util;
  
  import android.content.ContentProviderClient;
  import android.content.ContentResolver;
  import android.graphics.Bitmap;
  import android.graphics.Bitmap.Config;
  import android.graphics.Canvas;
  import android.graphics.ImageDecoder;
  import android.graphics.ImageDecoder.ImageInfo;
  import android.graphics.ImageDecoder.Source;
  import android.graphics.Matrix;
  import android.graphics.Paint;
  import android.graphics.Point;
  import android.graphics.PorterDuff;
  import android.graphics.drawable.BitmapDrawable;
  import android.graphics.drawable.Drawable;
  import android.net.Uri;
  import android.os.Bundle;
  import android.util.Size;
  
  import java.io.IOException;
  
  /**
   * 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 int[] mTempBuffer;
      private Bitmap mTempCompactBitmap;
      private Canvas mTempCompactBitmapCanvas;
      private Paint mTempCompactBitmapPaint;
      private final Matrix mTempMatrix = new Matrix();
  
      /**
       * Checks whether a bitmap is grayscale. Grayscale here means "very close to a perfect
       * gray".
       *
       * 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, Bitmap.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];
          }
      }
  
      /**
       * 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.
       *
       * 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;
      }
  
      /**
       * @see https://developer.android.com/topic/performance/graphics/load-bitmap
       */
      public static int calculateSampleSize(Size currentSize, Size requestedSize) {
          int inSampleSize = 1;
  
          if (currentSize.getHeight() > requestedSize.getHeight()
                  || currentSize.getWidth() > requestedSize.getWidth()) {
              final int halfHeight = currentSize.getHeight() / 2;
              final int halfWidth = currentSize.getWidth() / 2;
  
              // Calculate the largest inSampleSize value that is a power of 2 and keeps both
              // height and width larger than the requested height and width.
              while ((halfHeight / inSampleSize) >= requestedSize.getHeight()
                      && (halfWidth / inSampleSize) >= requestedSize.getWidth()) {
                  inSampleSize *= 2;
              }
          }
  
          return inSampleSize;
      }
  
      /**
       * Load a bitmap, and attempt to downscale to the required size, to save
       * on memory. Updated to use newer and more compatible ImageDecoder.
       *
       * @see https://developer.android.com/topic/performance/graphics/load-bitmap
       */
      public static Bitmap loadThumbnail(ContentResolver resolver, Uri uri, Size size)
              throws IOException {
  
          try (ContentProviderClient client = resolver.acquireContentProviderClient(uri)) {
              final Bundle opts = new Bundle();
              opts.putParcelable(ContentResolver.EXTRA_SIZE, Point.convert(size));
  
              return ImageDecoder.decodeBitmap(ImageDecoder.createSource(() -> {
                  return client.openTypedAssetFile(uri, "image/*", opts, null);
              }), (ImageDecoder decoder, ImageInfo info, Source source) -> {
                      decoder.setAllocator(ImageDecoder.ALLOCATOR_SOFTWARE);
  
                      final int sample = calculateSampleSize(info.getSize(), size);
                      if (sample > 1) {
                          decoder.setTargetSampleSize(sample);
                      }
                  });
          }
      }
  }
  