ShapeDetectionImpl: Android implementation of detectFace()

content/public/android/java/src/org/chromium/content/browser/shapedetection/ShapeDetectionImpl.java

Index: content/public/android/java/src/org/chromium/content/browser/shapedetection/ShapeDetectionImpl.java
diff --git a/content/public/android/java/src/org/chromium/content/browser/shapedetection/ShapeDetectionImpl.java b/content/public/android/java/src/org/chromium/content/browser/shapedetection/ShapeDetectionImpl.java
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index 0000000000000000000000000000000000000000..96bc8f2b8109f03a3cd4203d8fc42a438abf8443
--- /dev/null
+++ b/content/public/android/java/src/org/chromium/content/browser/shapedetection/ShapeDetectionImpl.java
@@ -0,0 +1,105 @@
+// 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.content.browser.shapedetection;
+
+import android.content.Context;
+import android.graphics.Bitmap;
+import android.graphics.PointF;
+import android.media.FaceDetector;
+import android.media.FaceDetector.Face;
+
+import org.chromium.blink.mojom.FaceDetectionResult;
+import org.chromium.blink.mojom.ShapeDetection;
+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 org.chromium.services.shell.InterfaceFactory;
+
+import java.nio.ByteBuffer;
+
+/**
+ * Android implementation of the shapedetection service defined in
+ * third_party/WebKit/public/platform/modules/shapedetection/shapedetection.mojom
+ */
+
+public class ShapeDetectionImpl implements ShapeDetection {
+    private static final String TAG = "ShapeDetectionImpl";
+    // By default, there is no limit in the number of faces detected.
+    private static final int MAX_FACES = 10;
+
+    public ShapeDetectionImpl() {}
+
+    @Override
+    public void detectFace(
+            SharedBufferHandle frameData, int width, int height, DetectFaceResponse callback) {
+        final int numBytes = width * height * 4;
+        ByteBuffer imageBuffer = frameData.map(0, numBytes, MapFlags.none());
+
+        Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
+        // An int array is needed to construct a bitmap. However the bytebuffer
+        // we get from sharedBufferHandle is directly allocated and does not
+        // have a supporting array. Therefore we need to create copy from
+        // bytebuffer to create this intermediate bitmap.

[mcasas, 2016/10/11 23:04:49]

If you are talking about types, use camel case:
Bitmap, ByteBuffer, SharedBufferHandle, Array,
If you're referring to a variable, put pipes around
it: |bitmap|.

Also: s/we need to create copy/we need to create a copy/

[xianglu, 2016/10/12 18:25:17]

Done.

+        bitmap.copyPixelsFromBuffer(imageBuffer);
+
+        // The bitmap must be in 565 format for findFaces() to work. See
+        // http://androidxref.com/7.0.0_r1/xref/frameworks/base/media/java/android/media/FaceDetector.java#124
+        //
+        // It turns out that facedetector is not able to detect correctly if

[mcasas, 2016/10/11 23:04:48]

Same here and in l.48: |bitmap|, FaceDetector.

nit: When a variable or data type is subject of the
phrase, it doesn't need "The":
// |bitmap| must be in 565 format...

[xianglu, 2016/10/12 18:25:17]

Done.

+        // you simply use pixmap.setConfig(). I believe this is because

[mcasas, 2016/10/11 23:04:48]

Maybe s/I believe this is/This might be/
Usually all code comments are written
in impersonal style ;)

[xianglu, 2016/10/12 18:25:17]

Done.

+        // findFaces() needs non-premultiplied ARGB arrangement, while the
+        // alphatype in original image is premultiplied. We can use getPixels()

[mcasas, 2016/10/11 23:04:49]

Here, not being subject, usually needs determinant:
...alpha type in _the_ original_ image...

[xianglu, 2016/10/12 18:25:17]

Done.

+        // which does the unmultiplication while copying to a new array. See
+        // http://androidxref.com/7.0.0_r1/xref/frameworks/base/graphics/java/android/graphics/Bitmap.java#538
+        int[] pixels = new int[width * height];
+        bitmap.getPixels(pixels, 0, width, 0, 0, width, height);
+        Bitmap bitmapUnpremul = Bitmap.createBitmap(pixels, width, height, Bitmap.Config.RGB_565);

[mcasas, 2016/10/11 23:04:48]

s/bitmpUnpremul/unPremultipliedBitmap/
(no abbreviations in variable names).

[xianglu, 2016/10/12 18:25:17]

Done.

+
+        FaceDetector detector = new FaceDetector(width, height, MAX_FACES);
+        Face[] detectedFaces = new Face[MAX_FACES];
+        final int numberOfFaces = detector.findFaces(bitmapUnpremul, detectedFaces);
+
+        FaceDetectionResult faceDetectionResult = new FaceDetectionResult();
+        faceDetectionResult.boundingBoxes = new RectF[numberOfFaces];
+        for (int i = 0; i < numberOfFaces; i++) {
+            final Face face = detectedFaces[i];
+            final PointF midPoint = new PointF();
+            face.getMidPoint(midPoint);
+            final float eyesDistance = face.eyesDistance();
+
+            RectF boundingBox = new RectF();
+            boundingBox.x = midPoint.x - eyesDistance;
+            boundingBox.y = midPoint.y - eyesDistance;
+            boundingBox.width = 2 * eyesDistance;
+            boundingBox.height = 2 * eyesDistance;
+
+            // TODO(xianglu): Consider adding Face.confidence and Face.pose.
+            faceDetectionResult.boundingBoxes[i] = boundingBox;
+        }
+
+        callback.call(faceDetectionResult);
+    }
+
+    @Override
+    public void close() {}
+
+    @Override
+    public void onConnectionError(MojoException e) {
+        close();
+    }
+
+    /**
+     * A factory method for registry in InterfaceRegistrarImpl.java.
+     */
+    public static class Factory implements InterfaceFactory<ShapeDetection> {
+        public Factory(Context context) {}
+
+        @Override
+        public ShapeDetection createImpl() {
+            return new ShapeDetectionImpl();
+        }
+    }
+}