src/com/android/photos/views/TiledImageRenderer.java - LeafOS-Project/android_packages_apps_Gallery2 - Gitiles

 /*
  * 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.views;

 import android.content.Context;
 import android.graphics.Bitmap;
 import android.graphics.Rect;
 import android.graphics.RectF;
 import android.support.v4.util.LongSparseArray;
 import android.util.DisplayMetrics;
 import android.util.Log;
 import android.view.View;
 import android.view.WindowManager;

 import com.android.gallery3d.common.Utils;
 import com.android.gallery3d.glrenderer.GLCanvas;
 import com.android.gallery3d.glrenderer.UploadedTexture;
 import com.android.photos.data.GalleryBitmapPool;

 public class TiledImageRenderer {
     public static final int SIZE_UNKNOWN = -1;

     private static final String TAG = "TiledImageRenderer";
     private static final int UPLOAD_LIMIT = 1;

     /*
      *  This is the tile state in the CPU side.
      *  Life of a Tile:
      *      ACTIVATED (initial state)
      *              --> IN_QUEUE - by queueForDecode()
      *              --> RECYCLED - by recycleTile()
      *      IN_QUEUE --> DECODING - by decodeTile()
      *               --> RECYCLED - by recycleTile)
      *      DECODING --> RECYCLING - by recycleTile()
      *               --> DECODED  - by decodeTile()
      *               --> DECODE_FAIL - by decodeTile()
      *      RECYCLING --> RECYCLED - by decodeTile()
      *      DECODED --> ACTIVATED - (after the decoded bitmap is uploaded)
      *      DECODED --> RECYCLED - by recycleTile()
      *      DECODE_FAIL -> RECYCLED - by recycleTile()
      *      RECYCLED --> ACTIVATED - by obtainTile()
      */
     private static final int STATE_ACTIVATED = 0x01;
     private static final int STATE_IN_QUEUE = 0x02;
     private static final int STATE_DECODING = 0x04;
     private static final int STATE_DECODED = 0x08;
     private static final int STATE_DECODE_FAIL = 0x10;
     private static final int STATE_RECYCLING = 0x20;
     private static final int STATE_RECYCLED = 0x40;

     private static GalleryBitmapPool sTilePool = GalleryBitmapPool.getInstance();

     // TILE_SIZE must be 2^N
     private int mTileSize;

     private TileSource mModel;
     protected int mLevelCount;  // cache the value of mScaledBitmaps.length

     // The mLevel variable indicates which level of bitmap we should use.
     // Level 0 means the original full-sized bitmap, and a larger value means
     // a smaller scaled bitmap (The width and height of each scaled bitmap is
     // half size of the previous one). If the value is in [0, mLevelCount), we
     // use the bitmap in mScaledBitmaps[mLevel] for display, otherwise the value
     // is mLevelCount
     private int mLevel = 0;

     private int mOffsetX;
     private int mOffsetY;

     private int mUploadQuota;
     private boolean mRenderComplete;

     private final RectF mSourceRect = new RectF();
     private final RectF mTargetRect = new RectF();

     private final LongSparseArray<Tile> mActiveTiles = new LongSparseArray<Tile>();

     // The following three queue are guarded by mQueueLock
     private final Object mQueueLock = new Object();
     private final TileQueue mRecycledQueue = new TileQueue();
     private final TileQueue mUploadQueue = new TileQueue();
     private final TileQueue mDecodeQueue = new TileQueue();

     // The width and height of the full-sized bitmap
     protected int mImageWidth = SIZE_UNKNOWN;
     protected int mImageHeight = SIZE_UNKNOWN;

     protected int mCenterX;
     protected int mCenterY;
     protected float mScale;
     protected int mRotation;

     private boolean mLayoutTiles;

     // Temp variables to avoid memory allocation
     private final Rect mTileRange = new Rect();
     private final Rect mActiveRange[] = {new Rect(), new Rect()};

     private TileDecoder mTileDecoder;
     private boolean mBackgroundTileUploaded;

     private int mViewWidth, mViewHeight;
     private View mParent;

     public static interface TileSource {
         public int getTileSize();
         public int getImageWidth();
         public int getImageHeight();

         // The tile returned by this method can be specified this way: Assuming
         // the image size is (width, height), first take the intersection of (0,
         // 0) - (width, height) and (x, y) - (x + tileSize, y + tileSize). If
         // in extending the region, we found some part of the region is outside
         // the image, those pixels are filled with black.
         //
         // If level > 0, it does the same operation on a down-scaled version of
         // the original image (down-scaled by a factor of 2^level), but (x, y)
         // still refers to the coordinate on the original image.
         //
         // The method would be called by the decoder thread.
         public Bitmap getTile(int level, int x, int y, Bitmap reuse);
     }

     public static int suggestedTileSize(Context context) {
         return isHighResolution(context) ? 512 : 256;
     }

     private static boolean isHighResolution(Context context) {
         DisplayMetrics metrics = new DisplayMetrics();
         WindowManager wm = (WindowManager)
                 context.getSystemService(Context.WINDOW_SERVICE);
         wm.getDefaultDisplay().getMetrics(metrics);
         return metrics.heightPixels > 2048 ||  metrics.widthPixels > 2048;
     }

     public TiledImageRenderer(View parent) {
         mParent = parent;
         mTileDecoder = new TileDecoder();
         mTileDecoder.start();
     }

     public int getViewWidth() {
         return mViewWidth;
     }

     public int getViewHeight() {
         return mViewHeight;
     }

     private void invalidate() {
         mParent.postInvalidate();
     }

     public void setModel(TileSource model, int rotation) {
         if (mModel != model) {
             mModel = model;
             notifyModelInvalidated();
         }
         if (mRotation != rotation) {
             mRotation = rotation;
             mLayoutTiles = true;
             invalidate();
         }
     }

     private static int calulateLevelCount(TileSource source) {
         int levels = 1;
         int maxDim = Math.max(source.getImageWidth(), source.getImageHeight());
         int t = source.getTileSize();
         while (t < maxDim) {
             t <<= 1;
             levels++;
         }
         return levels;
     }

     public void notifyModelInvalidated() {
         invalidateTiles();
         if (mModel == null) {
             mImageWidth = 0;
             mImageHeight = 0;
             mLevelCount = 0;
         } else {
             mImageWidth = mModel.getImageWidth();
             mImageHeight = mModel.getImageHeight();
             mLevelCount = calulateLevelCount(mModel);
             mTileSize = mModel.getTileSize();
         }
         mLayoutTiles = true;
         invalidate();
     }

     public void setViewSize(int width, int height) {
         mViewWidth = width;
         mViewHeight = height;
     }

     public void setPosition(int centerX, int centerY, float scale) {
         if (mCenterX == centerX && mCenterY == centerY
                 && mScale == scale) return;
         mCenterX = centerX;
         mCenterY = centerY;
         mScale = scale;
         mLayoutTiles = true;
         invalidate();
     }

     // Prepare the tiles we want to use for display.
     //
     // 1. Decide the tile level we want to use for display.
     // 2. Decide the tile levels we want to keep as texture (in addition to
     //    the one we use for display).
     // 3. Recycle unused tiles.
     // 4. Activate the tiles we want.
     private void layoutTiles() {
         if (mViewWidth == 0 || mViewHeight == 0 || !mLayoutTiles) {
             return;
         }
         mLayoutTiles = false;

         // The tile levels we want to keep as texture is in the range
         // [fromLevel, endLevel).
         int fromLevel;
         int endLevel;

         // We want to use a texture larger than or equal to the display size.
         mLevel = Utils.clamp(Utils.floorLog2(1f / mScale), 0, mLevelCount);

         // We want to keep one more tile level as texture in addition to what
         // we use for display. So it can be faster when the scale moves to the
         // next level. We choose the level closest to the current scale.
         if (mLevel != mLevelCount) {
             Rect range = mTileRange;
             getRange(range, mCenterX, mCenterY, mLevel, mScale, mRotation);
             mOffsetX = Math.round(mViewWidth / 2f + (range.left - mCenterX) * mScale);
             mOffsetY = Math.round(mViewHeight / 2f + (range.top - mCenterY) * mScale);
             fromLevel = mScale * (1 << mLevel) > 0.75f ? mLevel - 1 : mLevel;
         } else {
             // Activate the tiles of the smallest two levels.
             fromLevel = mLevel - 2;
             mOffsetX = Math.round(mViewWidth / 2f - mCenterX * mScale);
             mOffsetY = Math.round(mViewHeight / 2f - mCenterY * mScale);
         }

         fromLevel = Math.max(0, Math.min(fromLevel, mLevelCount - 2));
         endLevel = Math.min(fromLevel + 2, mLevelCount);

         Rect range[] = mActiveRange;
         for (int i = fromLevel; i < endLevel; ++i) {
             getRange(range[i - fromLevel], mCenterX, mCenterY, i, mRotation);
         }

         // If rotation is transient, don't update the tile.
         if (mRotation % 90 != 0) return;

         synchronized (mQueueLock) {
             mDecodeQueue.clean();
             mUploadQueue.clean();
             mBackgroundTileUploaded = false;

             // Recycle unused tiles: if the level of the active tile is outside the
             // range [fromLevel, endLevel) or not in the visible range.
             int n = mActiveTiles.size();
             for (int i = 0; i < n; i++) {
                 Tile tile = mActiveTiles.valueAt(i);
                 int level = tile.mTileLevel;
                 if (level < fromLevel || level >= endLevel
                         || !range[level - fromLevel].contains(tile.mX, tile.mY)) {
                     mActiveTiles.removeAt(i);
                     i--;
                     n--;
                     recycleTile(tile);
                 }
             }
         }

         for (int i = fromLevel; i < endLevel; ++i) {
             int size = mTileSize << i;
             Rect r = range[i - fromLevel];
             for (int y = r.top, bottom = r.bottom; y < bottom; y += size) {
                 for (int x = r.left, right = r.right; x < right; x += size) {
                     activateTile(x, y, i);
                 }
             }
         }
         invalidate();
     }

     private void invalidateTiles() {
         synchronized (mQueueLock) {
             mDecodeQueue.clean();
             mUploadQueue.clean();

             // TODO disable decoder
             int n = mActiveTiles.size();
             for (int i = 0; i < n; i++) {
                 Tile tile = mActiveTiles.valueAt(i);
                 recycleTile(tile);
             }
             mActiveTiles.clear();
         }
     }

     private void getRange(Rect out, int cX, int cY, int level, int rotation) {
         getRange(out, cX, cY, level, 1f / (1 << (level + 1)), rotation);
     }

     // If the bitmap is scaled by the given factor "scale", return the
     // rectangle containing visible range. The left-top coordinate returned is
     // aligned to the tile boundary.
     //
     // (cX, cY) is the point on the original bitmap which will be put in the
     // center of the ImageViewer.
     private void getRange(Rect out,
             int cX, int cY, int level, float scale, int rotation) {

         double radians = Math.toRadians(-rotation);
         double w = mViewWidth;
         double h = mViewHeight;

         double cos = Math.cos(radians);
         double sin = Math.sin(radians);
         int width = (int) Math.ceil(Math.max(
                 Math.abs(cos * w - sin * h), Math.abs(cos * w + sin * h)));
         int height = (int) Math.ceil(Math.max(
                 Math.abs(sin * w + cos * h), Math.abs(sin * w - cos * h)));

         int left = (int) Math.floor(cX - width / (2f * scale));
         int top = (int) Math.floor(cY - height / (2f * scale));
         int right = (int) Math.ceil(left + width / scale);
         int bottom = (int) Math.ceil(top + height / scale);

         // align the rectangle to tile boundary
         int size = mTileSize << level;
         left = Math.max(0, size * (left / size));
         top = Math.max(0, size * (top / size));
         right = Math.min(mImageWidth, right);
         bottom = Math.min(mImageHeight, bottom);

         out.set(left, top, right, bottom);
     }

     public void freeTextures() {
         mLayoutTiles = true;

         synchronized (mQueueLock) {
             mUploadQueue.clean();
             mDecodeQueue.clean();
             Tile tile = mRecycledQueue.pop();
             while (tile != null) {
                 tile.recycle();
                 tile = mRecycledQueue.pop();
             }
         }

         int n = mActiveTiles.size();
         for (int i = 0; i < n; i++) {
             Tile texture = mActiveTiles.valueAt(i);
             texture.recycle();
         }
         mActiveTiles.clear();
         mTileRange.set(0, 0, 0, 0);

         if (sTilePool != null) sTilePool.clear();
     }

     public void draw(GLCanvas canvas) {
         layoutTiles();
         uploadTiles(canvas);

         mUploadQuota = UPLOAD_LIMIT;
         mRenderComplete = true;

         int level = mLevel;
         int rotation = mRotation;
         int flags = 0;
         if (rotation != 0) flags |= GLCanvas.SAVE_FLAG_MATRIX;

         if (flags != 0) {
             canvas.save(flags);
             if (rotation != 0) {
                 int centerX = mViewWidth / 2, centerY = mViewHeight / 2;
                 canvas.translate(centerX, centerY);
                 canvas.rotate(rotation, 0, 0, 1);
                 canvas.translate(-centerX, -centerY);
             }
         }
         try {
             if (level != mLevelCount) {
                 int size = (mTileSize << level);
                 float length = size * mScale;
                 Rect r = mTileRange;

                 for (int ty = r.top, i = 0; ty < r.bottom; ty += size, i++) {
                     float y = mOffsetY + i * length;
                     for (int tx = r.left, j = 0; tx < r.right; tx += size, j++) {
                         float x = mOffsetX + j * length;
                         drawTile(canvas, tx, ty, level, x, y, length);
                     }
                 }
             }
         } finally {
             if (flags != 0) canvas.restore();
         }

         if (mRenderComplete) {
             if (!mBackgroundTileUploaded) {
                 uploadBackgroundTiles(canvas);
             }
         } else {
             invalidate();
         }
     }

     private void uploadBackgroundTiles(GLCanvas canvas) {
         mBackgroundTileUploaded = true;
         int n = mActiveTiles.size();
         for (int i = 0; i < n; i++) {
             Tile tile = mActiveTiles.valueAt(i);
             if (!tile.isContentValid()) {
                 queueForDecode(tile);
             }
         }
     }

     private void queueForUpload(Tile tile) {
         synchronized (mQueueLock) {
             mUploadQueue.push(tile);
         }
         invalidate();
         // TODO
 //        if (mTileUploader.mActive.compareAndSet(false, true)) {
 //            getGLRoot().addOnGLIdleListener(mTileUploader);
 //        }
     }

    private void queueForDecode(Tile tile) {
        synchronized (mQueueLock) {
            if (tile.mTileState == STATE_ACTIVATED) {
                tile.mTileState = STATE_IN_QUEUE;
                if (mDecodeQueue.push(tile)) {
                    mQueueLock.notifyAll();
                }
            }
        }
     }

     private boolean decodeTile(Tile tile) {
         synchronized (mQueueLock) {
             if (tile.mTileState != STATE_IN_QUEUE) return false;
             tile.mTileState = STATE_DECODING;
         }
         boolean decodeComplete = tile.decode();
         synchronized (mQueueLock) {
             if (tile.mTileState == STATE_RECYCLING) {
                 tile.mTileState = STATE_RECYCLED;
                 if (tile.mDecodedTile != null) {
                     if (sTilePool != null) sTilePool.put(tile.mDecodedTile);
                     tile.mDecodedTile = null;
                 }
                 mRecycledQueue.push(tile);
                 return false;
             }
             tile.mTileState = decodeComplete ? STATE_DECODED : STATE_DECODE_FAIL;
             return decodeComplete;
         }
     }

     private Tile obtainTile(int x, int y, int level) {
         synchronized (mQueueLock) {
             Tile tile = mRecycledQueue.pop();
             if (tile != null) {
                 tile.mTileState = STATE_ACTIVATED;
                 tile.update(x, y, level);
                 return tile;
             }
             return new Tile(x, y, level);
         }
     }

     private void recycleTile(Tile tile) {
         synchronized (mQueueLock) {
             if (tile.mTileState == STATE_DECODING) {
                 tile.mTileState = STATE_RECYCLING;
                 return;
             }
             tile.mTileState = STATE_RECYCLED;
             if (tile.mDecodedTile != null) {
                 if (sTilePool != null) sTilePool.put(tile.mDecodedTile);
                 tile.mDecodedTile = null;
             }
             mRecycledQueue.push(tile);
         }
     }

     private void activateTile(int x, int y, int level) {
         long key = makeTileKey(x, y, level);
         Tile tile = mActiveTiles.get(key);
         if (tile != null) {
             if (tile.mTileState == STATE_IN_QUEUE) {
                 tile.mTileState = STATE_ACTIVATED;
             }
             return;
         }
         tile = obtainTile(x, y, level);
         mActiveTiles.put(key, tile);
     }

     private Tile getTile(int x, int y, int level) {
         return mActiveTiles.get(makeTileKey(x, y, level));
     }

     private static long makeTileKey(int x, int y, int level) {
         long result = x;
         result = (result << 16) | y;
         result = (result << 16) | level;
         return result;
     }

     private void uploadTiles(GLCanvas canvas) {
         int quota = UPLOAD_LIMIT;
         Tile tile = null;
         while (quota > 0) {
             synchronized (mQueueLock) {
                 tile = mUploadQueue.pop();
             }
             if (tile == null) break;
             if (!tile.isContentValid()) {
                 Utils.assertTrue(tile.mTileState == STATE_DECODED);
                 tile.updateContent(canvas);
                 --quota;
             }
         }
         if (tile != null) {
             invalidate();
         }
     }

     // Draw the tile to a square at canvas that locates at (x, y) and
     // has a side length of length.
     private void drawTile(GLCanvas canvas,
             int tx, int ty, int level, float x, float y, float length) {
         RectF source = mSourceRect;
         RectF target = mTargetRect;
         target.set(x, y, x + length, y + length);
         source.set(0, 0, mTileSize, mTileSize);

         Tile tile = getTile(tx, ty, level);
         if (tile != null) {
             if (!tile.isContentValid()) {
                 if (tile.mTileState == STATE_DECODED) {
                     if (mUploadQuota > 0) {
                         --mUploadQuota;
                         tile.updateContent(canvas);
                     } else {
                         mRenderComplete = false;
                     }
                 } else if (tile.mTileState != STATE_DECODE_FAIL){
                     mRenderComplete = false;
                     queueForDecode(tile);
                 }
             }
             drawTile(tile, canvas, source, target);
         }
     }

     private boolean drawTile(
             Tile tile, GLCanvas canvas, RectF source, RectF target) {
         while (true) {
             if (tile.isContentValid()) {
                 canvas.drawTexture(tile, source, target);
                 return true;
             }

             // Parent can be divided to four quads and tile is one of the four.
             Tile parent = tile.getParentTile();
             if (parent == null) return false;
             if (tile.mX == parent.mX) {
                 source.left /= 2f;
                 source.right /= 2f;
             } else {
                 source.left = (mTileSize + source.left) / 2f;
                 source.right = (mTileSize + source.right) / 2f;
             }
             if (tile.mY == parent.mY) {
                 source.top /= 2f;
                 source.bottom /= 2f;
             } else {
                 source.top = (mTileSize + source.top) / 2f;
                 source.bottom = (mTileSize + source.bottom) / 2f;
             }
             tile = parent;
         }
     }

     private class Tile extends UploadedTexture {
         public int mX;
         public int mY;
         public int mTileLevel;
         public Tile mNext;
         public Bitmap mDecodedTile;
         public volatile int mTileState = STATE_ACTIVATED;

         public Tile(int x, int y, int level) {
             mX = x;
             mY = y;
             mTileLevel = level;
         }

         @Override
         protected void onFreeBitmap(Bitmap bitmap) {
             if (sTilePool != null) sTilePool.put(bitmap);
         }

         boolean decode() {
             // Get a tile from the original image. The tile is down-scaled
             // by (1 << mTilelevel) from a region in the original image.
             try {
                 Bitmap reuse = sTilePool.get(mTileSize, mTileSize);
                 mDecodedTile = mModel.getTile(mTileLevel, mX, mY, reuse);
             } catch (Throwable t) {
                 Log.w(TAG, "fail to decode tile", t);
             }
             return mDecodedTile != null;
         }

         @Override
         protected Bitmap onGetBitmap() {
             Utils.assertTrue(mTileState == STATE_DECODED);

             // We need to override the width and height, so that we won't
             // draw beyond the boundaries.
             int rightEdge = ((mImageWidth - mX) >> mTileLevel);
             int bottomEdge = ((mImageHeight - mY) >> mTileLevel);
             setSize(Math.min(mTileSize, rightEdge), Math.min(mTileSize, bottomEdge));

             Bitmap bitmap = mDecodedTile;
             mDecodedTile = null;
             mTileState = STATE_ACTIVATED;
             return bitmap;
         }

         // We override getTextureWidth() and getTextureHeight() here, so the
         // texture can be re-used for different tiles regardless of the actual
         // size of the tile (which may be small because it is a tile at the
         // boundary).
         @Override
         public int getTextureWidth() {
             return mTileSize;
         }

         @Override
         public int getTextureHeight() {
             return mTileSize;
         }

         public void update(int x, int y, int level) {
             mX = x;
             mY = y;
             mTileLevel = level;
             invalidateContent();
         }

         public Tile getParentTile() {
             if (mTileLevel + 1 == mLevelCount) return null;
             int size = mTileSize << (mTileLevel + 1);
             int x = size * (mX / size);
             int y = size * (mY / size);
             return getTile(x, y, mTileLevel + 1);
         }

         @Override
         public String toString() {
             return String.format("tile(%s, %s, %s / %s)",
                     mX / mTileSize, mY / mTileSize, mLevel, mLevelCount);
         }
     }

     private static class TileQueue {
         private Tile mHead;

         public Tile pop() {
             Tile tile = mHead;
             if (tile != null) mHead = tile.mNext;
             return tile;
         }

         public boolean push(Tile tile) {
             boolean wasEmpty = mHead == null;
             tile.mNext = mHead;
             mHead = tile;
             return wasEmpty;
         }

         public void clean() {
             mHead = null;
         }
     }

     private class TileDecoder extends Thread {

         public void finishAndWait() {
             interrupt();
             try {
                 join();
             } catch (InterruptedException e) {
                 Log.w(TAG, "Interrupted while waiting for TileDecoder thread to finish!");
             }
         }

         private Tile waitForTile() throws InterruptedException {
             synchronized(mQueueLock) {
                 while (true) {
                     Tile tile = mDecodeQueue.pop();
                     if (tile != null) {
                         return tile;
                     }
                     mQueueLock.wait();
                 }
             }
         }

         @Override
         public void run() {
             try {
                 while (!isInterrupted()) {
                     Tile tile = waitForTile();
                     if (decodeTile(tile)) {
                         queueForUpload(tile);
                     }
                 }
             } catch (InterruptedException ex) {
             }
         }

     }
 }
	/*
	* 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.views;

	import android.content.Context;
	import android.graphics.Bitmap;
	import android.graphics.Rect;
	import android.graphics.RectF;
	import android.support.v4.util.LongSparseArray;
	import android.util.DisplayMetrics;
	import android.util.Log;
	import android.view.View;
	import android.view.WindowManager;

	import com.android.gallery3d.common.Utils;
	import com.android.gallery3d.glrenderer.GLCanvas;
	import com.android.gallery3d.glrenderer.UploadedTexture;
	import com.android.photos.data.GalleryBitmapPool;

	public class TiledImageRenderer {
	public static final int SIZE_UNKNOWN = -1;

	private static final String TAG = "TiledImageRenderer";
	private static final int UPLOAD_LIMIT = 1;

	/*
	* This is the tile state in the CPU side.
	* Life of a Tile:
	* ACTIVATED (initial state)
	* --> IN_QUEUE - by queueForDecode()
	* --> RECYCLED - by recycleTile()
	* IN_QUEUE --> DECODING - by decodeTile()
	* --> RECYCLED - by recycleTile)
	* DECODING --> RECYCLING - by recycleTile()
	* --> DECODED - by decodeTile()
	* --> DECODE_FAIL - by decodeTile()
	* RECYCLING --> RECYCLED - by decodeTile()
	* DECODED --> ACTIVATED - (after the decoded bitmap is uploaded)
	* DECODED --> RECYCLED - by recycleTile()
	* DECODE_FAIL -> RECYCLED - by recycleTile()
	* RECYCLED --> ACTIVATED - by obtainTile()
	*/
	private static final int STATE_ACTIVATED = 0x01;
	private static final int STATE_IN_QUEUE = 0x02;
	private static final int STATE_DECODING = 0x04;
	private static final int STATE_DECODED = 0x08;
	private static final int STATE_DECODE_FAIL = 0x10;
	private static final int STATE_RECYCLING = 0x20;
	private static final int STATE_RECYCLED = 0x40;

	private static GalleryBitmapPool sTilePool = GalleryBitmapPool.getInstance();

	// TILE_SIZE must be 2^N
	private int mTileSize;

	private TileSource mModel;
	protected int mLevelCount; // cache the value of mScaledBitmaps.length

	// The mLevel variable indicates which level of bitmap we should use.
	// Level 0 means the original full-sized bitmap, and a larger value means
	// a smaller scaled bitmap (The width and height of each scaled bitmap is
	// half size of the previous one). If the value is in [0, mLevelCount), we
	// use the bitmap in mScaledBitmaps[mLevel] for display, otherwise the value
	// is mLevelCount
	private int mLevel = 0;

	private int mOffsetX;
	private int mOffsetY;

	private int mUploadQuota;
	private boolean mRenderComplete;

	private final RectF mSourceRect = new RectF();
	private final RectF mTargetRect = new RectF();

	private final LongSparseArray<Tile> mActiveTiles = new LongSparseArray<Tile>();

	// The following three queue are guarded by mQueueLock
	private final Object mQueueLock = new Object();
	private final TileQueue mRecycledQueue = new TileQueue();
	private final TileQueue mUploadQueue = new TileQueue();
	private final TileQueue mDecodeQueue = new TileQueue();

	// The width and height of the full-sized bitmap
	protected int mImageWidth = SIZE_UNKNOWN;
	protected int mImageHeight = SIZE_UNKNOWN;

	protected int mCenterX;
	protected int mCenterY;
	protected float mScale;
	protected int mRotation;

	private boolean mLayoutTiles;

	// Temp variables to avoid memory allocation
	private final Rect mTileRange = new Rect();
	private final Rect mActiveRange[] = {new Rect(), new Rect()};

	private TileDecoder mTileDecoder;
	private boolean mBackgroundTileUploaded;

	private int mViewWidth, mViewHeight;
	private View mParent;

	public static interface TileSource {
	public int getTileSize();
	public int getImageWidth();
	public int getImageHeight();

	// The tile returned by this method can be specified this way: Assuming
	// the image size is (width, height), first take the intersection of (0,
	// 0) - (width, height) and (x, y) - (x + tileSize, y + tileSize). If
	// in extending the region, we found some part of the region is outside
	// the image, those pixels are filled with black.
	//
	// If level > 0, it does the same operation on a down-scaled version of
	// the original image (down-scaled by a factor of 2^level), but (x, y)
	// still refers to the coordinate on the original image.
	//
	// The method would be called by the decoder thread.
	public Bitmap getTile(int level, int x, int y, Bitmap reuse);
	}

	public static int suggestedTileSize(Context context) {
	return isHighResolution(context) ? 512 : 256;
	}

	private static boolean isHighResolution(Context context) {
	DisplayMetrics metrics = new DisplayMetrics();
	WindowManager wm = (WindowManager)
	context.getSystemService(Context.WINDOW_SERVICE);
	wm.getDefaultDisplay().getMetrics(metrics);
	return metrics.heightPixels > 2048 \|\| metrics.widthPixels > 2048;
	}

	public TiledImageRenderer(View parent) {
	mParent = parent;
	mTileDecoder = new TileDecoder();
	mTileDecoder.start();
	}

	public int getViewWidth() {
	return mViewWidth;
	}

	public int getViewHeight() {
	return mViewHeight;
	}

	private void invalidate() {
	mParent.postInvalidate();
	}

	public void setModel(TileSource model, int rotation) {
	if (mModel != model) {
	mModel = model;
	notifyModelInvalidated();
	}
	if (mRotation != rotation) {
	mRotation = rotation;
	mLayoutTiles = true;
	invalidate();
	}
	}

	private static int calulateLevelCount(TileSource source) {
	int levels = 1;
	int maxDim = Math.max(source.getImageWidth(), source.getImageHeight());
	int t = source.getTileSize();
	while (t < maxDim) {
	t <<= 1;
	levels++;
	}
	return levels;
	}

	public void notifyModelInvalidated() {
	invalidateTiles();
	if (mModel == null) {
	mImageWidth = 0;
	mImageHeight = 0;
	mLevelCount = 0;
	} else {
	mImageWidth = mModel.getImageWidth();
	mImageHeight = mModel.getImageHeight();
	mLevelCount = calulateLevelCount(mModel);
	mTileSize = mModel.getTileSize();
	}
	mLayoutTiles = true;
	invalidate();
	}

	public void setViewSize(int width, int height) {
	mViewWidth = width;
	mViewHeight = height;
	}

	public void setPosition(int centerX, int centerY, float scale) {
	if (mCenterX == centerX && mCenterY == centerY
	&& mScale == scale) return;
	mCenterX = centerX;
	mCenterY = centerY;
	mScale = scale;
	mLayoutTiles = true;
	invalidate();
	}

	// Prepare the tiles we want to use for display.
	//
	// 1. Decide the tile level we want to use for display.
	// 2. Decide the tile levels we want to keep as texture (in addition to
	// the one we use for display).
	// 3. Recycle unused tiles.
	// 4. Activate the tiles we want.
	private void layoutTiles() {
	if (mViewWidth == 0 \|\| mViewHeight == 0 \|\| !mLayoutTiles) {
	return;
	}
	mLayoutTiles = false;

	// The tile levels we want to keep as texture is in the range
	// [fromLevel, endLevel).
	int fromLevel;
	int endLevel;

	// We want to use a texture larger than or equal to the display size.
	mLevel = Utils.clamp(Utils.floorLog2(1f / mScale), 0, mLevelCount);

	// We want to keep one more tile level as texture in addition to what
	// we use for display. So it can be faster when the scale moves to the
	// next level. We choose the level closest to the current scale.
	if (mLevel != mLevelCount) {
	Rect range = mTileRange;
	getRange(range, mCenterX, mCenterY, mLevel, mScale, mRotation);
	mOffsetX = Math.round(mViewWidth / 2f + (range.left - mCenterX) * mScale);
	mOffsetY = Math.round(mViewHeight / 2f + (range.top - mCenterY) * mScale);
	fromLevel = mScale * (1 << mLevel) > 0.75f ? mLevel - 1 : mLevel;
	} else {
	// Activate the tiles of the smallest two levels.
	fromLevel = mLevel - 2;
	mOffsetX = Math.round(mViewWidth / 2f - mCenterX * mScale);
	mOffsetY = Math.round(mViewHeight / 2f - mCenterY * mScale);
	}

	fromLevel = Math.max(0, Math.min(fromLevel, mLevelCount - 2));
	endLevel = Math.min(fromLevel + 2, mLevelCount);

	Rect range[] = mActiveRange;
	for (int i = fromLevel; i < endLevel; ++i) {
	getRange(range[i - fromLevel], mCenterX, mCenterY, i, mRotation);
	}

	// If rotation is transient, don't update the tile.
	if (mRotation % 90 != 0) return;

	synchronized (mQueueLock) {
	mDecodeQueue.clean();
	mUploadQueue.clean();
	mBackgroundTileUploaded = false;

	// Recycle unused tiles: if the level of the active tile is outside the
	// range [fromLevel, endLevel) or not in the visible range.
	int n = mActiveTiles.size();
	for (int i = 0; i < n; i++) {
	Tile tile = mActiveTiles.valueAt(i);
	int level = tile.mTileLevel;
	if (level < fromLevel \|\| level >= endLevel
	\|\| !range[level - fromLevel].contains(tile.mX, tile.mY)) {
	mActiveTiles.removeAt(i);
	i--;
	n--;
	recycleTile(tile);
	}
	}
	}

	for (int i = fromLevel; i < endLevel; ++i) {
	int size = mTileSize << i;
	Rect r = range[i - fromLevel];
	for (int y = r.top, bottom = r.bottom; y < bottom; y += size) {
	for (int x = r.left, right = r.right; x < right; x += size) {
	activateTile(x, y, i);
	}
	}
	}
	invalidate();
	}

	private void invalidateTiles() {
	synchronized (mQueueLock) {
	mDecodeQueue.clean();
	mUploadQueue.clean();

	// TODO disable decoder
	int n = mActiveTiles.size();
	for (int i = 0; i < n; i++) {
	Tile tile = mActiveTiles.valueAt(i);
	recycleTile(tile);
	}
	mActiveTiles.clear();
	}
	}

	private void getRange(Rect out, int cX, int cY, int level, int rotation) {
	getRange(out, cX, cY, level, 1f / (1 << (level + 1)), rotation);
	}

	// If the bitmap is scaled by the given factor "scale", return the
	// rectangle containing visible range. The left-top coordinate returned is
	// aligned to the tile boundary.
	//
	// (cX, cY) is the point on the original bitmap which will be put in the
	// center of the ImageViewer.
	private void getRange(Rect out,
	int cX, int cY, int level, float scale, int rotation) {

	double radians = Math.toRadians(-rotation);
	double w = mViewWidth;
	double h = mViewHeight;

	double cos = Math.cos(radians);
	double sin = Math.sin(radians);
	int width = (int) Math.ceil(Math.max(
	Math.abs(cos * w - sin * h), Math.abs(cos * w + sin * h)));
	int height = (int) Math.ceil(Math.max(
	Math.abs(sin * w + cos * h), Math.abs(sin * w - cos * h)));

	int left = (int) Math.floor(cX - width / (2f * scale));
	int top = (int) Math.floor(cY - height / (2f * scale));
	int right = (int) Math.ceil(left + width / scale);
	int bottom = (int) Math.ceil(top + height / scale);

	// align the rectangle to tile boundary
	int size = mTileSize << level;
	left = Math.max(0, size * (left / size));
	top = Math.max(0, size * (top / size));
	right = Math.min(mImageWidth, right);
	bottom = Math.min(mImageHeight, bottom);

	out.set(left, top, right, bottom);
	}

	public void freeTextures() {
	mLayoutTiles = true;

	synchronized (mQueueLock) {
	mUploadQueue.clean();
	mDecodeQueue.clean();
	Tile tile = mRecycledQueue.pop();
	while (tile != null) {
	tile.recycle();
	tile = mRecycledQueue.pop();
	}
	}

	int n = mActiveTiles.size();
	for (int i = 0; i < n; i++) {
	Tile texture = mActiveTiles.valueAt(i);
	texture.recycle();
	}
	mActiveTiles.clear();
	mTileRange.set(0, 0, 0, 0);

	if (sTilePool != null) sTilePool.clear();
	}

	public void draw(GLCanvas canvas) {
	layoutTiles();
	uploadTiles(canvas);

	mUploadQuota = UPLOAD_LIMIT;
	mRenderComplete = true;

	int level = mLevel;
	int rotation = mRotation;
	int flags = 0;
	if (rotation != 0) flags \|= GLCanvas.SAVE_FLAG_MATRIX;

	if (flags != 0) {
	canvas.save(flags);
	if (rotation != 0) {
	int centerX = mViewWidth / 2, centerY = mViewHeight / 2;
	canvas.translate(centerX, centerY);
	canvas.rotate(rotation, 0, 0, 1);
	canvas.translate(-centerX, -centerY);
	}
	}
	try {
	if (level != mLevelCount) {
	int size = (mTileSize << level);
	float length = size * mScale;
	Rect r = mTileRange;

	for (int ty = r.top, i = 0; ty < r.bottom; ty += size, i++) {
	float y = mOffsetY + i * length;
	for (int tx = r.left, j = 0; tx < r.right; tx += size, j++) {
	float x = mOffsetX + j * length;
	drawTile(canvas, tx, ty, level, x, y, length);
	}
	}
	}
	} finally {
	if (flags != 0) canvas.restore();
	}

	if (mRenderComplete) {
	if (!mBackgroundTileUploaded) {
	uploadBackgroundTiles(canvas);
	}
	} else {
	invalidate();
	}
	}

	private void uploadBackgroundTiles(GLCanvas canvas) {
	mBackgroundTileUploaded = true;
	int n = mActiveTiles.size();
	for (int i = 0; i < n; i++) {
	Tile tile = mActiveTiles.valueAt(i);
	if (!tile.isContentValid()) {
	queueForDecode(tile);
	}
	}
	}

	private void queueForUpload(Tile tile) {
	synchronized (mQueueLock) {
	mUploadQueue.push(tile);
	}
	invalidate();
	// TODO
	// if (mTileUploader.mActive.compareAndSet(false, true)) {
	// getGLRoot().addOnGLIdleListener(mTileUploader);
	// }
	}

	private void queueForDecode(Tile tile) {
	synchronized (mQueueLock) {
	if (tile.mTileState == STATE_ACTIVATED) {
	tile.mTileState = STATE_IN_QUEUE;
	if (mDecodeQueue.push(tile)) {
	mQueueLock.notifyAll();
	}
	}
	}
	}

	private boolean decodeTile(Tile tile) {
	synchronized (mQueueLock) {
	if (tile.mTileState != STATE_IN_QUEUE) return false;
	tile.mTileState = STATE_DECODING;
	}
	boolean decodeComplete = tile.decode();
	synchronized (mQueueLock) {
	if (tile.mTileState == STATE_RECYCLING) {
	tile.mTileState = STATE_RECYCLED;
	if (tile.mDecodedTile != null) {
	if (sTilePool != null) sTilePool.put(tile.mDecodedTile);
	tile.mDecodedTile = null;
	}
	mRecycledQueue.push(tile);
	return false;
	}
	tile.mTileState = decodeComplete ? STATE_DECODED : STATE_DECODE_FAIL;
	return decodeComplete;
	}
	}

	private Tile obtainTile(int x, int y, int level) {
	synchronized (mQueueLock) {
	Tile tile = mRecycledQueue.pop();
	if (tile != null) {
	tile.mTileState = STATE_ACTIVATED;
	tile.update(x, y, level);
	return tile;
	}
	return new Tile(x, y, level);
	}
	}

	private void recycleTile(Tile tile) {
	synchronized (mQueueLock) {
	if (tile.mTileState == STATE_DECODING) {
	tile.mTileState = STATE_RECYCLING;
	return;
	}
	tile.mTileState = STATE_RECYCLED;
	if (tile.mDecodedTile != null) {
	if (sTilePool != null) sTilePool.put(tile.mDecodedTile);
	tile.mDecodedTile = null;
	}
	mRecycledQueue.push(tile);
	}
	}

	private void activateTile(int x, int y, int level) {
	long key = makeTileKey(x, y, level);
	Tile tile = mActiveTiles.get(key);
	if (tile != null) {
	if (tile.mTileState == STATE_IN_QUEUE) {
	tile.mTileState = STATE_ACTIVATED;
	}
	return;
	}
	tile = obtainTile(x, y, level);
	mActiveTiles.put(key, tile);
	}

	private Tile getTile(int x, int y, int level) {
	return mActiveTiles.get(makeTileKey(x, y, level));
	}

	private static long makeTileKey(int x, int y, int level) {
	long result = x;
	result = (result << 16) \| y;
	result = (result << 16) \| level;
	return result;
	}

	private void uploadTiles(GLCanvas canvas) {
	int quota = UPLOAD_LIMIT;
	Tile tile = null;
	while (quota > 0) {
	synchronized (mQueueLock) {
	tile = mUploadQueue.pop();
	}
	if (tile == null) break;
	if (!tile.isContentValid()) {
	Utils.assertTrue(tile.mTileState == STATE_DECODED);
	tile.updateContent(canvas);
	--quota;
	}
	}
	if (tile != null) {
	invalidate();
	}
	}

	// Draw the tile to a square at canvas that locates at (x, y) and
	// has a side length of length.
	private void drawTile(GLCanvas canvas,
	int tx, int ty, int level, float x, float y, float length) {
	RectF source = mSourceRect;
	RectF target = mTargetRect;
	target.set(x, y, x + length, y + length);
	source.set(0, 0, mTileSize, mTileSize);

	Tile tile = getTile(tx, ty, level);
	if (tile != null) {
	if (!tile.isContentValid()) {
	if (tile.mTileState == STATE_DECODED) {
	if (mUploadQuota > 0) {
	--mUploadQuota;
	tile.updateContent(canvas);
	} else {
	mRenderComplete = false;
	}
	} else if (tile.mTileState != STATE_DECODE_FAIL){
	mRenderComplete = false;
	queueForDecode(tile);
	}
	}
	drawTile(tile, canvas, source, target);
	}
	}

	private boolean drawTile(
	Tile tile, GLCanvas canvas, RectF source, RectF target) {
	while (true) {
	if (tile.isContentValid()) {
	canvas.drawTexture(tile, source, target);
	return true;
	}

	// Parent can be divided to four quads and tile is one of the four.
	Tile parent = tile.getParentTile();
	if (parent == null) return false;
	if (tile.mX == parent.mX) {
	source.left /= 2f;
	source.right /= 2f;
	} else {
	source.left = (mTileSize + source.left) / 2f;
	source.right = (mTileSize + source.right) / 2f;
	}
	if (tile.mY == parent.mY) {
	source.top /= 2f;
	source.bottom /= 2f;
	} else {
	source.top = (mTileSize + source.top) / 2f;
	source.bottom = (mTileSize + source.bottom) / 2f;
	}
	tile = parent;
	}
	}

	private class Tile extends UploadedTexture {
	public int mX;
	public int mY;
	public int mTileLevel;
	public Tile mNext;
	public Bitmap mDecodedTile;
	public volatile int mTileState = STATE_ACTIVATED;

	public Tile(int x, int y, int level) {
	mX = x;
	mY = y;
	mTileLevel = level;
	}

	@Override
	protected void onFreeBitmap(Bitmap bitmap) {
	if (sTilePool != null) sTilePool.put(bitmap);
	}

	boolean decode() {
	// Get a tile from the original image. The tile is down-scaled
	// by (1 << mTilelevel) from a region in the original image.
	try {
	Bitmap reuse = sTilePool.get(mTileSize, mTileSize);
	mDecodedTile = mModel.getTile(mTileLevel, mX, mY, reuse);
	} catch (Throwable t) {
	Log.w(TAG, "fail to decode tile", t);
	}
	return mDecodedTile != null;
	}

	@Override
	protected Bitmap onGetBitmap() {
	Utils.assertTrue(mTileState == STATE_DECODED);

	// We need to override the width and height, so that we won't
	// draw beyond the boundaries.
	int rightEdge = ((mImageWidth - mX) >> mTileLevel);
	int bottomEdge = ((mImageHeight - mY) >> mTileLevel);
	setSize(Math.min(mTileSize, rightEdge), Math.min(mTileSize, bottomEdge));

	Bitmap bitmap = mDecodedTile;
	mDecodedTile = null;
	mTileState = STATE_ACTIVATED;
	return bitmap;
	}

	// We override getTextureWidth() and getTextureHeight() here, so the
	// texture can be re-used for different tiles regardless of the actual
	// size of the tile (which may be small because it is a tile at the
	// boundary).
	@Override
	public int getTextureWidth() {
	return mTileSize;
	}

	@Override
	public int getTextureHeight() {
	return mTileSize;
	}

	public void update(int x, int y, int level) {
	mX = x;
	mY = y;
	mTileLevel = level;
	invalidateContent();
	}

	public Tile getParentTile() {
	if (mTileLevel + 1 == mLevelCount) return null;
	int size = mTileSize << (mTileLevel + 1);
	int x = size * (mX / size);
	int y = size * (mY / size);
	return getTile(x, y, mTileLevel + 1);
	}

	@Override
	public String toString() {
	return String.format("tile(%s, %s, %s / %s)",
	mX / mTileSize, mY / mTileSize, mLevel, mLevelCount);
	}
	}

	private static class TileQueue {
	private Tile mHead;

	public Tile pop() {
	Tile tile = mHead;
	if (tile != null) mHead = tile.mNext;
	return tile;
	}

	public boolean push(Tile tile) {
	boolean wasEmpty = mHead == null;
	tile.mNext = mHead;
	mHead = tile;
	return wasEmpty;
	}

	public void clean() {
	mHead = null;
	}
	}

	private class TileDecoder extends Thread {

	public void finishAndWait() {
	interrupt();
	try {
	join();
	} catch (InterruptedException e) {
	Log.w(TAG, "Interrupted while waiting for TileDecoder thread to finish!");
	}
	}

	private Tile waitForTile() throws InterruptedException {
	synchronized(mQueueLock) {
	while (true) {
	Tile tile = mDecodeQueue.pop();
	if (tile != null) {
	return tile;
	}
	mQueueLock.wait();
	}
	}
	}

	@Override
	public void run() {
	try {
	while (!isInterrupted()) {
	Tile tile = waitForTile();
	if (decodeTile(tile)) {
	queueForUpload(tile);
	}
	}
	} catch (InterruptedException ex) {
	}
	}

	}
	}