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
new file mode 100644
index 0000000000000000000000000000000000000000..ab0a8a2ca949b9b26deb71f3c9a5c3fa505bb01c
--- /dev/null
+++ b/content/public/android/java/src/org/chromium/content/browser/shapedetection/ShapeDetectionImpl.java
@@ -0,0 +1,97 @@
+// 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
+ *
+ * TEST=
+ * https://rawgit.com/Nadia-mint/chrome-demos/shapedetection/shapedetection.html

[mcasas, 2016/10/11 02:51:18]

This line should go in the CL description (below
the BUG=...).

[xianglu, 2016/10/11 20:25:50]

Done.

+ */
+
+public class ShapeDetectionImpl implements ShapeDetection {
+    private static final String TAG = "ShapeDetectionImpl";
+    private static final int MAX_FACES = 10;
+
+    public ShapeDetectionImpl(Context context) {}
+
+    @Override
+    public void detectFace(
+            SharedBufferHandle frameData, int width, int height, DetectFaceResponse callback) {
+        int numBytes = width * height * 4;

[mcasas, 2016/10/11 02:51:18]

nit: make this final, also in l.53, l. 58, 59, 61
and wherever else makes sense.

[xianglu, 2016/10/11 20:25:50]

Done.

+        ByteBuffer imageBuffer = frameData.map(0, numBytes, MapFlags.none());
+
+        Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
+        bitmap.copyPixelsFromBuffer(imageBuffer);
+
+        // Convert ARGB_8888 bitmap to array-backed RGB_565 bitmap.
+        int[] pixels = new int[width * height];
+        bitmap.getPixels(pixels, 0, width, 0, 0, width, height);
+        Bitmap bitmap2 = Bitmap.createBitmap(pixels, width, height, Bitmap.Config.RGB_565);

[mcasas, 2016/10/11 02:51:18]

Ok, IIUC here we do two copies:
|imageBuffer| --> |bitmap| and
|bitmap| --> |bitmap2|, if this is the
only way, we need to document it properly,
so developers of the future won't be left
scratching their heads.

Also, would this [1]

bitmap.reconfigure(width, height, Bitmap.Config.RGB_565;

work?

(even better: bitmap.setConfig(Bitmap.Config.RGB_565);
would do the same, if it works -- this would need a
sizable comment, since it's not evident that a simple
setBla() will do that much work).

[1]
https://developer.android.com/reference/android/graphics/Bitmap.html#reconfig...,
int, android.graphics.Bitmap.Config)

[xianglu, 2016/10/11 20:25:50]

I tried bitmap.setConfig(), but it seems FaceDetector doesn't work correctly
with it.
I have to make this intermediate int array as a workaround.

+
+        FaceDetector detector = new FaceDetector(width, height, MAX_FACES);
+        Face[] detectedFaces = new Face[MAX_FACES];
+        int numberOfFaces = detector.findFaces(bitmap2, detectedFaces);
+
+        FaceDetectionResult faceDetectionResult = new FaceDetectionResult();
+        faceDetectionResult.boundingBoxes = new RectF[numberOfFaces];
+        for (int i = 0; i < numberOfFaces; i++) {
+            Face face = detectedFaces[i];
+            PointF midPoint = new PointF();
+            face.getMidPoint(midPoint);
+            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;
+
+            faceDetectionResult.boundingBoxes[i] = boundingBox;

[mcasas, 2016/10/11 02:51:18]

Please add a TODO(xianglu) here with something
like:
// TODO(xianglu): consider adding Face.confidence and Face.pose as well.

[xianglu, 2016/10/11 20:25:50]

Done.

+        }
+
+        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> {
+        private Context mContext;
+        public Factory(Context context) {
+            mContext = context;
+        }
+
+        @Override
+        public ShapeDetection createImpl() {
+            return new ShapeDetectionImpl(mContext);

[mcasas, 2016/10/11 02:51:18]

I think we don't really need |context| here nor
in ShapeDetectionImpl, so we can just not hold 
on to it in this file.

[xianglu, 2016/10/11 20:25:50]

Done.

+        }
+    }
+}