1. A computer implemented method, comprising: receiving, by one or more processors of a client device, a set of images in a video stream, the set of images including at least a portion of a face, each pixel in the set of images having a first intensity value; converting, by the one or more processors of the client device, one or more images of the set of images to a set of single channel images, the set of single channel images corresponding to a single channel associated with an aspect of the face; generating a set of approximation images from the set of single channel images, the set of approximation images generated by, for each pixel, replacing a second intensity value with an approximation value, the second intensity value of a pixel being an intensity value of the pixel within a single channel image of the set of single channel images, the approximation value generated as a logarithm of the first intensity value and the second intensity value; and generating a set of binarized images by thresholding the set of approximation images, wherein thresholding the set of approximation images is based on a threshold intensity value corresponding to a fractional luminance value of at least a portion of the set of images.