Shape Detection: QR detection in Chrome Android using Play Services

chrome/android/java/src/org/chromium/chrome/browser/shapedetection/BarcodeDetectionImpl.java

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.chrome.browser.shapedetection;
+
+import android.content.Context;
+import android.graphics.Bitmap;
+import android.graphics.Rect;
+import android.util.SparseArray;
+
+import com.google.android.gms.common.ConnectionResult;
+import com.google.android.gms.common.GoogleApiAvailability;
+import com.google.android.gms.vision.Frame;
+import com.google.android.gms.vision.barcode.Barcode;
+import com.google.android.gms.vision.barcode.BarcodeDetector;
+
+import org.chromium.base.Log;
+import org.chromium.blink.mojom.BarcodeDetection;
+import org.chromium.blink.mojom.BarcodeDetectionResult;
+import org.chromium.gfx.mojom.RectF;
+import org.chromium.mojo.system.MojoException;
+import org.chromium.mojo.system.SharedBufferHandle;
+import org.chromium.mojo.system.SharedBufferHandle.MapFlags;
+
+import java.nio.ByteBuffer;
+
+/**
+ * Implementation of mojo BarcodeDetection, using Google Play Services vision package.
+ */
+public class BarcodeDetectionImpl implements BarcodeDetection {
+    private static final String TAG = "BarcodeDetectionImpl";
+
+    // https://cs.chromium.org/chromium/src/mojo/edk/system/broker_host.cc?l=24
+    private static final int MOJO_SHAREDBUFFER_MAX_BYTES = 16 * 1024 * 1024;
+
+    private final Context mContext;
+    private BarcodeDetector mBarcodeDetector;
+
+    public BarcodeDetectionImpl(Context context) {
+        Log.d(TAG, "BarcodeDetectionImpl ctor()");
+        mContext = context;
+        mBarcodeDetector = new BarcodeDetector.Builder(mContext).build();
+    }
+
+    @Override
+    public void detect(
+            SharedBufferHandle frameData, int width, int height, DetectResponse callback) {
+        if (GoogleApiAvailability.getInstance().isGooglePlayServicesAvailable(mContext)

[dgn, 2016/11/24 10:32:32]

Consider using ExternalAuthUtils#canUseGooglePlayService() for chrome-standard
way of handling missing gmscore

[mcasas, 2016/11/28 22:03:37]

Done.

+                != ConnectionResult.SUCCESS) {
+            Log.e(TAG, "Google Play Services not available");
+            callback.call(new BarcodeDetectionResult[0]);
+            return;
+        }
+        // The vision library will be downloaded the first time the API is used
+        // on the device; this happens "fast", but it might have not completed,
+        // bail in this case. Also, the API was disabled between and v.9.0 and
+        // v.9.2, see https://developers.google.com/android/guides/releases.
+        if (!mBarcodeDetector.isOperational()) {
+            Log.e(TAG, "BarcodeDetector is not operational");
+            callback.call(new BarcodeDetectionResult[0]);
+            return;
+        }
+
+        final long numPixels = (long) width * height;
+        if (!frameData.isValid() || width <= 0 || height <= 0
+                || numPixels > MOJO_SHAREDBUFFER_MAX_BYTES / 4) {

[dcheng, 2016/11/24 04:31:39]

Drive-by: this number can (and has) changed over time. Just check the result of
the map(): if the map() fails, then we can assume the number is invalid.

Also, I know java doesn't have unsigned... but what are mojo's guarantees here?
It should know it's reading an unsigned off the wire, but what happens if the
unsigned > int?

[mcasas, 2016/11/28 22:03:37]

Done.
Since you posted this in the chromium-mojo@ mailing 
list, I guess we'll take it there.

+            callback.call(new BarcodeDetectionResult[0]);
+            return;
+        }
+
+        ByteBuffer imageBuffer = frameData.map(0, numPixels * 4, MapFlags.none());
+        if (imageBuffer.capacity() <= 0) {
+            callback.call(new BarcodeDetectionResult[0]);
+            return;
+        }
+
+        Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
+        bitmap.copyPixelsFromBuffer(imageBuffer);
+
+        Frame frame = null;
+        try {
+            // This constructor implies a pixel format conversion to YUV.
+            frame = new Frame.Builder().setBitmap(bitmap).build();
+        } catch (IllegalArgumentException | IllegalStateException ex) {
+            Log.e(TAG, "Frame.Builder().setBitmap() or build(): " + ex);
+            callback.call(new BarcodeDetectionResult[0]);
+            return;
+        }
+
+        final SparseArray<Barcode> barcodes = mBarcodeDetector.detect(frame);
+
+        BarcodeDetectionResult[] barcodeArray = new BarcodeDetectionResult[barcodes.size()];
+        for (int i = 0; i < barcodes.size(); i++) {
+            barcodeArray[i] = new BarcodeDetectionResult();
+            final Barcode barcode = barcodes.valueAt(i);
+            barcodeArray[i].rawValue = barcode.rawValue;
+            final Rect rect = barcode.getBoundingBox();
+            barcodeArray[i].boundingBox = new RectF();
+            barcodeArray[i].boundingBox.x = rect.left;
+            barcodeArray[i].boundingBox.y = rect.top;
+            barcodeArray[i].boundingBox.width = rect.width();
+            barcodeArray[i].boundingBox.height = rect.height();
+        }
+        callback.call(barcodeArray);
+    }
+
+    @Override
+    public void close() {
+        mBarcodeDetector.release();
+    }
+
+    @Override
+    public void onConnectionError(MojoException e) {
+        close();
+    }
+
+}