Emotion Recognition is used for categorizing the emotions into one of the 6 emotions through the images of face. Intially viola jones or other face detection algorithm is used for detecting the faces. Preprocessing is also used for standardizing the images into same sizes.
Facial Feature extraction is used in a number of applications including emotion detection. In the following approach various popular feature descriptors, including Gabor features, HOG, DWT were computed. We have fused features using Multiview Distance Metric Learning (MDML) which
utilizes complementary features of the images to extract every known detail while eliminating the redundant features. Moreover MDML maps the features extracted from the dataset to higher discriminative space. The features belonging to the same class are brought closer and those that are from different classes are forced away by the MDML thereby increasing the accuracy of the classifier employed. CK+ Dataset has been used to conduct the experiments. Experimental results
represent the efficacy of the method is 93.5% displaying the potential of the recommended manner.
The human facial expressions contain clues to the emotional state of a person. Computation of emotion of a human through facial expression has been a central topic of Human Computer Interaction (HCI) research and a concern for researchers. The machines can utilize an emotion detection tool to understand the human emotions better and respond accordingly. Facial Expressions have been analyzed and put to use by various researchers such as in  the pain level can be recognized by detecting the facial expression. It can be used in case of patients who are mute or are not able to speak because of a disorder.  judges the concentration level of a viewer watching an advertisement. It has been employed for detecting various mental disorders such as depression and anxiety in .
As Paul Ekman showed in , the emotions are universally expressed in the same way regardless of the culture, nationality etc. Subtlety, variance of facial expression and complex nature of emotion further complicate the process. Six emotions have been defined by  in his paper. They are happy, Anger, Sad, Surprise, disgust and fear. Emotion detection is accomplished in three basic steps.
Firstly, the images are preprocessed and a high quality facial image is extracted from the original image from the dataset.
Secondly, feature descriptors are applied to the image for feature extraction. After the dimension reduction by a dimension reduction algorithm such as PCA, LDA, etc a classifier is used for classifying the image into one of emotion.
Since the Extended Cohn Kanade Dataset used is free from illumination variance, occlusion and head pose are some of the major concerns in many other datasets results shown are superior than most of the previous methods.
The proposed approach is novel in detecting and computing the emotions through Multiview Distance Metric Learning (MDML) introduced in . The similar looking data from different classes are often misclassified. MDML helps to reduce this misclassification and fuses the results of various feature descriptors and extracts complementary features from them.
Moreover MDML maps the features extracted from the dataset to higher discriminative space. The features having affinity to the same emotion are brought closer while those having affinity to different emotion classes are moved as far as possible. The classifier is trained using this data.
- A. Emotion recognition
The primary step in emotion detection is the localization of the face. CK+ dataset has been recorded in a controlled having illumination invariance and free from any occlusions. Hence, the facial image is always present in the image and priorly the face’s global position is known. Since wide variations are present in the scale and yaw, pitch, roll of the face, accurately localizing the face in different images is a very challenging task. The various obstructions and hindrances such as glasses and facial hair further complicates the task .
Viola-Jones  found an efficient answer for localizing the face. This method is based on AdaBoost learning and Haar-like features. Earlier it was developed for finding and detecting objects in an image . It granted fast object detection for the task of real time usage. Keeping in mind the accuracy of the method, it is used for face localization.
- B. Feature Descriptor
Feature extraction indicates deriving pertinent data from the preprocessed, gray scaled images from dataset, that will be employed for the intent of emotion detection. It is a defying task due to the above mentioned reasons. A comprehensive method is to derive descriptors from images is to use Log-Gabor filters as done in  by nominating the random bandwidth for making the Log-Gabor filter. Another attainable answer is to use model based method for the facial expression recognition . The authors in  constructed a light source and subject independent global representation of expressions by discovering of the set of 322 image sequences in CK+ database.  utilizes LBP features and finds the emotion.
- C. Multiview Distance Metric Learning
Motivated by the discriminative mapping and better results of MDML we are using MDML proposed by  which attracts the features of the same class together and pushes away that belong to the different class. The data is then mapped to higher discriminative space and complementary features are extracted from the dataset. This ensures all the details of the image are taken into account. MDML pulls the similar data together and pushes away the different data away. In  the
authors used MDML for Pain intensity classification.
- D. Facial Expression Classification
Finally, after being mapped to higher discriminative space features are enforced into the classifier for identification of the six emotions. The most sought after classifiers include template matching, rule based classifier, neural networks and support vector machines (SVM). In SVM, a hyperplane is constructed with ample distance among the different emotion classes during the training phase.
While during test phase, the trained SVM model classifies the test image to one of the emotion classes. In  the authors utilize SVM with linear kernel for expression classification. There are six basic emotion classes which are Anger, Disgust, Happy, Sad, Surprise and Fear for analysis of proposed algorithm.
The author of this blog is working currently with Nayan
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