SVGTileProvider.java

/*
 * Copyright 2014 Google Inc. All rights reserved.
 *
 * 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.google.samples.apps.iosched.ui;

import android.graphics.*;
import android.util.Log;

import com.google.android.gms.maps.model.Tile;
import com.google.android.gms.maps.model.TileProvider;

import java.io.*;
import java.util.concurrent.ConcurrentLinkedQueue;

import com.larvalabs.svgandroid.SVG;
import com.larvalabs.svgandroid.SVGBuilder;

import static com.google.samples.apps.iosched.util.LogUtils.makeLogTag;

public class SVGTileProvider implements TileProvider {
    private static final String TAG = makeLogTag(SVGTileProvider.class);

    private static final int POOL_MAX_SIZE = 5;
    private static final int BASE_TILE_SIZE = 256;

    private final TileGeneratorPool mPool;

    private final Matrix mBaseMatrix;

    private final int mScale;
    private final int mDimension;

    /**
     * NOTE: must use a synchronize block when using {@link android.graphics.Picture#draw(android.graphics.Canvas)}
     */
    private final Picture mSvgPicture;

    public SVGTileProvider(File file, float dpi) throws IOException {
        mScale = Math.round(dpi + .3f); // Make it look nice on N7 (1.3 dpi)
        mDimension = BASE_TILE_SIZE * mScale;

        mPool = new TileGeneratorPool(POOL_MAX_SIZE);

        SVG svg = new SVGBuilder().readFromInputStream(new FileInputStream(file)).build();
        mSvgPicture = svg.getPicture();
        RectF limits = svg.getLimits();

        mBaseMatrix = new Matrix();
        mBaseMatrix.setPolyToPoly(
                new float[]{
                        0, 0,
                        limits.width(), 0,
                        limits.width(), limits.height()
                }, 0,
                new float[]{
                        40.95635986328125f, 98.94217824936158f,
                        40.95730018615723f, 98.94123077396628f,
                        40.95791244506836f, 98.94186019897214f
                }, 0, 3
        );
    }

    @Override
    public Tile getTile(int x, int y, int zoom) {
        TileGenerator tileGenerator = mPool.get();
        byte[] tileData = tileGenerator.getTileImageData(x, y, zoom);
        mPool.restore(tileGenerator);
        return new Tile(mDimension, mDimension, tileData);
    }

    private class TileGeneratorPool {
        private final ConcurrentLinkedQueue<TileGenerator> mPool = new ConcurrentLinkedQueue<TileGenerator>();
        private final int mMaxSize;

        private TileGeneratorPool(int maxSize) {
            mMaxSize = maxSize;
        }

        public TileGenerator get() {
            TileGenerator i = mPool.poll();
            if (i == null) {
                return new TileGenerator();
            }
            return i;
        }

        public void restore(TileGenerator tileGenerator) {
            if (mPool.size() < mMaxSize && mPool.offer(tileGenerator)) {
                return;
            }
            // pool is too big or returning to pool failed, so just try to clean
            // up.
            tileGenerator.cleanUp();
        }
    }

    public class TileGenerator {
        private Bitmap mBitmap;
        private ByteArrayOutputStream mStream;

        public TileGenerator() {
            mBitmap = Bitmap.createBitmap(mDimension, mDimension, Bitmap.Config.ARGB_8888);
            mStream = new ByteArrayOutputStream(mDimension * mDimension * 4);
        }

        public byte[] getTileImageData(int x, int y, int zoom) {
            mStream.reset();

            Matrix matrix = new Matrix(mBaseMatrix);
            float scale = (float) (Math.pow(2, zoom) * mScale);
            matrix.postScale(scale, scale);
            matrix.postTranslate(-x * mDimension, -y * mDimension);

            mBitmap.eraseColor(Color.TRANSPARENT);
            Canvas c = new Canvas(mBitmap);
            c.setMatrix(matrix);

            // NOTE: Picture is not thread-safe.
            synchronized (mSvgPicture) {
                mSvgPicture.draw(c);
            }

            BufferedOutputStream stream = new BufferedOutputStream(mStream);
            mBitmap.compress(Bitmap.CompressFormat.PNG, 0, stream);
            try {
                stream.close();
            } catch (IOException e) {
                Log.e(TAG, "Error while closing tile byte stream.");
                e.printStackTrace();
            }
            return mStream.toByteArray();
        }

        /**
         * Attempt to free memory and remove references.
         */
        public void cleanUp() {
            mBitmap.recycle();
            mBitmap = null;
            try {
                mStream.close();
            } catch (IOException e) {
                // ignore
            }
            mStream = null;
        }
    }
}