1 files changed, 158 insertions, 0 deletions
diff --git a/library/src/main/java/com/davemorrissey/labs/subscaleview/decoder/SkiaImageRegionDecoder.java b/library/src/main/java/com/davemorrissey/labs/subscaleview/decoder/SkiaImageRegionDecoder.java
new file mode 100644
index 0000000..eebe2bb
--- /dev/null
+++ b/library/src/main/java/com/davemorrissey/labs/subscaleview/decoder/SkiaImageRegionDecoder.java
@@ -0,0 +1,158 @@
+package com.davemorrissey.labs.subscaleview.decoder;
+
+import android.content.ContentResolver;
+import android.content.Context;
+import android.content.pm.PackageManager;
+import android.content.res.AssetManager;
+import android.content.res.Resources;
+import android.graphics.*;
+import android.net.Uri;
+import android.os.Build;
+import android.support.annotation.Keep;
+import android.text.TextUtils;
+
+import com.davemorrissey.labs.subscaleview.SubsamplingScaleImageView;
+
+import java.io.InputStream;
+import java.util.List;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReadWriteLock;
+import java.util.concurrent.locks.ReentrantReadWriteLock;
+
+/**
+ * Default implementation of {@link com.davemorrissey.labs.subscaleview.decoder.ImageRegionDecoder}
+ * using Android's {@link android.graphics.BitmapRegionDecoder}, based on the Skia library. This
+ * works well in most circumstances and has reasonable performance due to the cached decoder instance,
+ * however it has some problems with grayscale, indexed and CMYK images.
+ *
+ * A {@link ReadWriteLock} is used to delegate responsibility for multi threading behaviour to the
+ * {@link BitmapRegionDecoder} instance on SDK &gt;= 21, whilst allowing this class to block until no
+ * tiles are being loaded before recycling the decoder. In practice, {@link BitmapRegionDecoder} is
+ * synchronized internally so this has no real impact on performance.
+ */
+public class SkiaImageRegionDecoder implements ImageRegionDecoder {
+
+    private BitmapRegionDecoder decoder;
+    private final ReadWriteLock decoderLock = new ReentrantReadWriteLock(true);
+
+    private static final String FILE_PREFIX = "file://";
+    private static final String ASSET_PREFIX = FILE_PREFIX + "/android_asset/";
+    private static final String RESOURCE_PREFIX = ContentResolver.SCHEME_ANDROID_RESOURCE + "://";
+
+    private final Bitmap.Config bitmapConfig;
+
+    @Keep
+    @SuppressWarnings("unused")
+    public SkiaImageRegionDecoder() {
+        this(null);
+    }
+
+    @SuppressWarnings({"WeakerAccess", "SameParameterValue"})
+    public SkiaImageRegionDecoder(Bitmap.Config bitmapConfig) {
+        Bitmap.Config globalBitmapConfig = SubsamplingScaleImageView.getPreferredBitmapConfig();
+        if (bitmapConfig != null) {
+            this.bitmapConfig = bitmapConfig;
+        } else if (globalBitmapConfig != null) {
+            this.bitmapConfig = globalBitmapConfig;
+        } else {
+            this.bitmapConfig = Bitmap.Config.RGB_565;
+        }
+    }
+
+    @Override
+    public Point init(Context context, Uri uri) throws Exception {
+        String uriString = uri.toString();
+        if (uriString.startsWith(RESOURCE_PREFIX)) {
+            Resources res;
+            String packageName = uri.getAuthority();
+            if (context.getPackageName().equals(packageName)) {
+                res = context.getResources();
+            } else {
+                PackageManager pm = context.getPackageManager();
+                res = pm.getResourcesForApplication(packageName);
+            }
+
+            int id = 0;
+            List<String> segments = uri.getPathSegments();
+            int size = segments.size();
+            if (size == 2 && segments.get(0).equals("drawable")) {
+                String resName = segments.get(1);
+                id = res.getIdentifier(resName, "drawable", packageName);
+            } else if (size == 1 && TextUtils.isDigitsOnly(segments.get(0))) {
+                try {
+                    id = Integer.parseInt(segments.get(0));
+                } catch (NumberFormatException ignored) {
+                }
+            }
+
+            decoder = BitmapRegionDecoder.newInstance(context.getResources().openRawResource(id), false);
+        } else if (uriString.startsWith(ASSET_PREFIX)) {
+            String assetName = uriString.substring(ASSET_PREFIX.length());
+            decoder = BitmapRegionDecoder.newInstance(context.getAssets().open(assetName, AssetManager.ACCESS_RANDOM), false);
+        } else if (uriString.startsWith(FILE_PREFIX)) {
+            decoder = BitmapRegionDecoder.newInstance(uriString.substring(FILE_PREFIX.length()), false);
+        } else {
+            InputStream inputStream = null;
+            try {
+                ContentResolver contentResolver = context.getContentResolver();
+                inputStream = contentResolver.openInputStream(uri);
+                decoder = BitmapRegionDecoder.newInstance(inputStream, false);
+            } finally {
+                if (inputStream != null) {
+                    try { inputStream.close(); } catch (Exception e) { /* Ignore */ }
+                }
+            }
+        }
+        return new Point(decoder.getWidth(), decoder.getHeight());
+    }
+
+    @Override
+    public Bitmap decodeRegion(Rect sRect, int sampleSize) {
+        getDecodeLock().lock();
+        try {
+            if (decoder != null && !decoder.isRecycled()) {
+                BitmapFactory.Options options = new BitmapFactory.Options();
+                options.inSampleSize = sampleSize;
+                options.inPreferredConfig = bitmapConfig;
+                Bitmap bitmap = decoder.decodeRegion(sRect, options);
+                if (bitmap == null) {
+                    throw new RuntimeException("Skia image decoder returned null bitmap - image format may not be supported");
+                }
+                return bitmap;
+            } else {
+                throw new IllegalStateException("Cannot decode region after decoder has been recycled");
+            }
+        } finally {
+            getDecodeLock().unlock();
+        }
+    }
+
+    @Override
+    public synchronized boolean isReady() {
+        return decoder != null && !decoder.isRecycled();
+    }
+
+    @Override
+    public synchronized void recycle() {
+        decoderLock.writeLock().lock();
+        try {
+            decoder.recycle();
+            decoder = null;
+        } finally {
+            decoderLock.writeLock().unlock();
+        }
+    }
+
+    /**
+     * Before SDK 21, BitmapRegionDecoder was not synchronized internally. Any attempt to decode
+     * regions from multiple threads with one decoder instance causes a segfault. For old versions
+     * use the write lock to enforce single threaded decoding.
+     */
+    private Lock getDecodeLock() {
+        if (Build.VERSION.SDK_INT < 21) {
+            return decoderLock.writeLock();
+        } else {
+            return decoderLock.readLock();
+        }
+    }
+}