Java and haarcascade face and mouth detection - mouth as the nose : <p>Today I begin to test the project which detects a smile in Java and OpenCv. To recognition face and mouth project used haarcascade_frontalface_alt and haarcascade_mcs_mouth But i don't understand why in some reasons project detect nose as a mouth. 
I have two methods:</p>

<pre><code>private ArrayList&lt;Mat&gt; detectMouth(String filename) {
    int i = 0;
    ArrayList&lt;Mat&gt; mouths = new ArrayList&lt;Mat&gt;();
    // reading image in grayscale from the given path
    image = Highgui.imread(filename, Highgui.CV_LOAD_IMAGE_GRAYSCALE);
    MatOfRect faceDetections = new MatOfRect();
    // detecting face(s) on given image and saving them to MatofRect object
    faceDetector.detectMultiScale(image, faceDetections);
    System.out.println(String.format("Detected %s faces", faceDetections.toArray().length));
    MatOfRect mouthDetections = new MatOfRect();
    // detecting mouth(s) on given image and saving them to MatOfRect object
    mouthDetector.detectMultiScale(image, mouthDetections);
    System.out.println(String.format("Detected %s mouths", mouthDetections.toArray().length));
    for (Rect face : faceDetections.toArray()) {
        Mat outFace = image.submat(face);
        // saving cropped face to picture
        Highgui.imwrite("face" + i + ".png", outFace);
        for (Rect mouth : mouthDetections.toArray()) {
            // trying to find right mouth
            // if the mouth is in the lower 2/5 of the face
            // and the lower edge of mouth is above of the face
            // and the horizontal center of the mouth is the enter of the face
            if (mouth.y &gt; face.y + face.height * 3 / 5 &amp;&amp; mouth.y + mouth.height &lt; face.y + face.height
                    &amp;&amp; Math.abs((mouth.x + mouth.width / 2)) - (face.x + face.width / 2) &lt; face.width / 10) {
                Mat outMouth = image.submat(mouth);
                // resizing mouth to the unified size of trainSize
                Imgproc.resize(outMouth, outMouth, trainSize);
                mouths.add(outMouth);
                // saving mouth to picture 
                Highgui.imwrite("mouth" + i + ".png", outMouth);
                i++;
            }
        }
    }
    return mouths;
}
</code></pre>

<p>and detect smile</p>

<pre><code>private void detectSmile(ArrayList&lt;Mat&gt; mouths) {
        trainSVM();
        CvSVMParams params = new CvSVMParams();
        // set linear kernel (no mapping, regression is done in the original feature space)
        params.set_kernel_type(CvSVM.LINEAR);
    // train SVM with images in trainingImages, labels in trainingLabels, given params with empty samples
        clasificador = new CvSVM(trainingImages, trainingLabels, new Mat(), new Mat(), params);
        // save generated SVM to file, so we can see what it generated
        clasificador.save("svm.xml");
        // loading previously saved file
        clasificador.load("svm.xml");
        // returnin, if there aren't any samples
        if (mouths.isEmpty()) {
            System.out.println("No mouth detected");
            return;
        }
        for (Mat mouth : mouths) {
            Mat out = new Mat();
            // converting to 32 bit floating point in gray scale
            mouth.convertTo(out, CvType.CV_32FC1);
            if (clasificador.predict(out.reshape(1, 1)) == 1.0) {
                System.out.println("Detected happy face");
            } else {
                System.out.println("Detected not a happy face");
            }
        }
    }
</code></pre>

<p>Examples:</p>

<p>For that picture </p>

<p><a href="https://i.stack.imgur.com/9b83D.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/9b83D.jpg" alt="enter image description here"></a></p>

<p>correctly detects this mounth:</p>

<p><a href="https://i.stack.imgur.com/ikQpM.png" rel="noreferrer"><img src="https://i.stack.imgur.com/ikQpM.png" alt="enter image description here"></a></p>

<p>but in other picture </p>

<p><a href="https://i.stack.imgur.com/t7Hg8.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/t7Hg8.jpg" alt="enter image description here"></a></p>

<p>nose is detected
<a href="https://i.stack.imgur.com/uFWLa.png" rel="noreferrer"><img src="https://i.stack.imgur.com/uFWLa.png" alt="enter image description here"></a></p>

<p>What's the problem in your opinion ?</p>
