“…Ultimately, all these key points are finding blobs. The size of the blob is determined by the value of σ. Viola-Jones object detection, face detection [53], pedestrian detection [57] • takes less computational time while maintaining high accuracy in real-time [53] • can detect object under complex situation (i.e. rain , snow) [53] • can successfully detect pedestrian in low resolution [54] • lacks the entire image fine details [55], [56] • texture or shape information are ignored [55], [56] • sensitive to lighting condition [55], [56] • unsuitable for general object detection [55], [56] SIFT object recognition, face recognition [58], gesture recognition [59], video tracking [60], motion tracking [61] • robust to occlusion, clutter and noise [62] • distinctive features [62] • performance is close to real-time [63] • flexible to extend with other features [64] • poor performance with lighting changes and blur [65] • computationally expensive [65] PCA-SIFT object recognition, image retrieval [66], image analysis [65] • reduces the dimensionality of the SIFT descriptors [66] • improves the matching accuracy and speed in real-world environment [66] • sensitive to viewpoint change [65] • color information is ignored [67] SURF object recognition [51], [68], face detection [69], image registration [66], object classification [70] • takes less time for computation and feature matching [51] • improves the robustness of feature extraction [51] • struggl...…”