Figure 2

GRAB feature extraction. From left to right: An image is first smoothed using GRAB window operator. During smoothing, each pixel of the image is replaced by the average of the original intensities of the N×N region surrounding it. In this figure, N is 3. Next, the neighborhood operator is applied on the smoothed image. Each pixel is compared with its neighbors on the smoothed image. In this figure, radius of the neighborhood is 1. The value of a pixel is the binary pattern obtained by thresholding the pixel with its neighbors. A face image is divided into multiple regions and GRAB histograms are generated.