Face Alignment and Chipping:
Face alignment is critical for the accuracy of our face recognition software. As a result, prior to chipping the individual seal faces, we aligned them using the manually tagged eye locations in each photo by performing in-plane rotation to align the eyes along the x-axis. Once the eyes are manually located in each photo, the GUI automatically aligns and chips the faces to the desired size (e.g., 112x112 pixels). We followed an approach similar to that used by the developers of LemurFaceID to align faces: Given \((l_{x},\ l_{y})\) and\((r_{x},\ r_{y})\) to be the center of the left and right eyes respectively, one can calculate the rotation matrix M to be used in an affine transformation of the image. Let\(x=\frac{l_{x}\ +\ r_{x}\ }{2}\)and\(y=\ \frac{l_{y}\ +\ r_{y}\ }{2}\) and\(\theta=atan(\frac{r_{\text{y\ }}-\ l_{y}}{r_{x}-l_{x}})\), so\((x,\ y)\) will be the location of the midpoint between the centers of the two eyes and \(\theta\) be the rotational angle. Then M will be calculated as: