Android 人脸检测 MaxNumDetectedFaces

Question

所以我刚刚将我的平板电脑(原华硕变形金刚)升级到安卓版本 4.0.3 以构建一个使用人脸检测的应用程序。但是每次我启动它并尝试开始人脸检测时，我都会在 logcat 中收到此错误:

E/AndroidRuntime(1755): java.lang.IllegalArgumentException: invalid face detection type=0

我在文档中读到这意味着可以检测到或支持 0 张面孔，但这是否意味着我的设备根本无法检测到面孔，或者我可以更改吗？另外它使用后置摄像头，将其更改为另一个摄像头会改变什么吗？我一直在尝试这样做，但我无法弄清楚如何，可以在此处找到我尝试运行的项目:

https://docs.google.com/open?id=0B2Nu5U2Cz81qZExGQ25sWVdRd21IOExUUTZsZzFoZw

来自这个 SO 问题: Android face detector using android camera

Answer 1

请记住，您可以使用较旧的 FaceDetector API 检测人脸.它从 API 级别 1 开始就存在，应该可以在所有带摄像头的手机上使用。它还会在检测到人脸时返回一个边界框。

public Rect findFace(Bitmap bmp) {
    // Ask for 1 face
    Face faces[] = new FaceDetector.Face[1];
    FaceDetector detector = new FaceDetector( bmp.getWidth(), bmp.getHeight(), 1 );
    int count = detector.findFaces( bmp, faces );

    Face face = null;

    if( count > 0 ) {
        face = faces[0];

        PointF midEyes = new PointF();
        face.getMidPoint( midEyes );
        Log.i( TAG,
                "Found face. Confidence: " + face.confidence() + ". Eye Distance: " + face.eyesDistance() + " Pose: ("
                        + face.pose( FaceDetector.Face.EULER_X ) + "," + face.pose( FaceDetector.Face.EULER_Y ) + ","
                        + face.pose( FaceDetector.Face.EULER_Z ) + "). Eye Midpoint: (" + midEyes.x + "," + midEyes.y + ")" );

        float eyedist = face.eyesDistance();
        PointF lt = new PointF( midEyes.x - eyedist * 2.0f, midEyes.y - eyedist * 2.5f );
        // Create rectangle around face.  Create a box based on the eyes and add some padding.
        // The ratio of head height to width is generally 9/5 but that makes the rect a bit to tall.
        return new Rect(
            Math.max( (int) ( lt.x ), 0 ),
            Math.max( (int) ( lt.y ), 0 ),
            Math.min( (int) ( lt.x + eyedist * 4.0f ), bmp.getWidth() ),
            Math.min( (int) ( lt.y + eyedist * 5.5f ), bmp.getHeight() )
        );
    }

    return null;
}