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diff --git a/src/com/android/photos/data/GalleryBitmapPool.java b/src/com/android/photos/data/GalleryBitmapPool.java
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+++ b/src/com/android/photos/data/GalleryBitmapPool.java
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+/*
+ * Copyright (C) 2013 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.photos.data;
+
+import android.graphics.Bitmap;
+import android.graphics.Point;
+import android.util.Pools.Pool;
+import android.util.Pools.SynchronizedPool;
+
+import com.android.photos.data.SparseArrayBitmapPool.Node;
+
+/**
+ * Pool allowing the efficient reuse of bitmaps in order to avoid long
+ * garbage collection pauses.
+ */
+public class GalleryBitmapPool {
+
+    private static final int CAPACITY_BYTES = 20971520;
+
+    // We found that Gallery uses bitmaps that are either square (for example,
+    // tiles of large images or square thumbnails), match one of the common
+    // photo aspect ratios (4x3, 3x2, or 16x9), or, less commonly, are of some
+    // other aspect ratio. Taking advantage of this information, we use 3
+    // SparseArrayBitmapPool instances to back the GalleryBitmapPool, which affords
+    // O(1) lookups for square bitmaps, and average-case - but *not* asymptotically -
+    // O(1) lookups for common photo aspect ratios and other miscellaneous aspect
+    // ratios. Beware of the pathological case where there are many bitmaps added
+    // to the pool with different non-square aspect ratios but the same width, as
+    // performance will degrade and the average case lookup will approach
+    // O(# of different aspect ratios).
+    private static final int POOL_INDEX_NONE = -1;
+    private static final int POOL_INDEX_SQUARE = 0;
+    private static final int POOL_INDEX_PHOTO = 1;
+    private static final int POOL_INDEX_MISC = 2;
+
+    private static final Point[] COMMON_PHOTO_ASPECT_RATIOS =
+        { new Point(4, 3), new Point(3, 2), new Point(16, 9) };
+
+    private int mCapacityBytes;
+    private SparseArrayBitmapPool [] mPools;
+    private Pool<Node> mSharedNodePool = new SynchronizedPool<Node>(128);
+
+    private GalleryBitmapPool(int capacityBytes) {
+        mPools = new SparseArrayBitmapPool[3];
+        mPools[POOL_INDEX_SQUARE] = new SparseArrayBitmapPool(capacityBytes / 3, mSharedNodePool);
+        mPools[POOL_INDEX_PHOTO] = new SparseArrayBitmapPool(capacityBytes / 3, mSharedNodePool);
+        mPools[POOL_INDEX_MISC] = new SparseArrayBitmapPool(capacityBytes / 3, mSharedNodePool);
+        mCapacityBytes = capacityBytes;
+    }
+
+    private static GalleryBitmapPool sInstance = new GalleryBitmapPool(CAPACITY_BYTES);
+
+    public static GalleryBitmapPool getInstance() {
+        return sInstance;
+    }
+
+    private SparseArrayBitmapPool getPoolForDimensions(int width, int height) {
+        int index = getPoolIndexForDimensions(width, height);
+        if (index == POOL_INDEX_NONE) {
+            return null;
+        } else {
+            return mPools[index];
+        }
+    }
+
+    private int getPoolIndexForDimensions(int width, int height) {
+        if (width <= 0 || height <= 0) {
+            return POOL_INDEX_NONE;
+        }
+        if (width == height) {
+            return POOL_INDEX_SQUARE;
+        }
+        int min, max;
+        if (width > height) {
+            min = height;
+            max = width;
+        } else {
+            min = width;
+            max = height;
+        }
+        for (Point ar : COMMON_PHOTO_ASPECT_RATIOS) {
+            if (min * ar.x == max * ar.y) {
+                return POOL_INDEX_PHOTO;
+            }
+        }
+        return POOL_INDEX_MISC;
+    }
+
+    /**
+     * @return Capacity of the pool in bytes.
+     */
+    public synchronized int getCapacity() {
+        return mCapacityBytes;
+    }
+
+    /**
+     * @return Approximate total size in bytes of the bitmaps stored in the pool.
+     */
+    public int getSize() {
+        // Note that this only returns an approximate size, since multiple threads
+        // might be getting and putting Bitmaps from the pool and we lock at the
+        // sub-pool level to avoid unnecessary blocking.
+        int total = 0;
+        for (SparseArrayBitmapPool p : mPools) {
+            total += p.getSize();
+        }
+        return total;
+    }
+
+    /**
+     * @return Bitmap from the pool with the desired height/width or null if none available.
+     */
+    public Bitmap get(int width, int height) {
+        SparseArrayBitmapPool pool = getPoolForDimensions(width, height);
+        if (pool == null) {
+            return null;
+        } else {
+            return pool.get(width, height);
+        }
+    }
+
+    /**
+     * Adds the given bitmap to the pool.
+     * @return Whether the bitmap was added to the pool.
+     */
+    public boolean put(Bitmap b) {
+        if (b == null || b.getConfig() != Bitmap.Config.ARGB_8888) {
+            return false;
+        }
+        SparseArrayBitmapPool pool = getPoolForDimensions(b.getWidth(), b.getHeight());
+        if (pool == null) {
+            b.recycle();
+            return false;
+        } else {
+            return pool.put(b);
+        }
+    }
+
+    /**
+     * Empty the pool, recycling all the bitmaps currently in it.
+     */
+    public void clear() {
+        for (SparseArrayBitmapPool p : mPools) {
+            p.clear();
+        }
+    }
+}