face_aligner.py

# import the necessary packages
import numpy as np
import cv2

class FaceAligner:
	def __init__(self, desiredLeftEye=(0.4, 0.4),
		desiredFaceWidth=256, desiredFaceHeight=None):
		self.desiredLeftEye = desiredLeftEye
		self.desiredFaceWidth = desiredFaceWidth
		self.desiredFaceHeight = desiredFaceHeight

		# if the desired face height is None, set it to be the
		# desired face width (normal behavior)
		if self.desiredFaceHeight is None:
			self.desiredFaceHeight = self.desiredFaceWidth

	def align(self, image, points):

		# compute the center of mass for each eye
		leftEyeCenter = (int(points[0]), int(points[5]))
		rightEyeCenter = (int(points[1]), int(points[6]))

		# compute the angle between the eye centroids
		dY = rightEyeCenter[1] - leftEyeCenter[1]
		dX = rightEyeCenter[0] - leftEyeCenter[0]
		angle = np.degrees(np.arctan2(dY, dX))

		# compute the desired right eye x-coordinate based on the
		# desired x-coordinate of the left eye
		desiredRightEyeX = 1.0 - self.desiredLeftEye[0]

		# determine the scale of the new resulting image by taking
		# the ratio of the distance between eyes in the *current*
		# image to the ratio of distance between eyes in the
		# *desired* image
		dist = np.sqrt((dX ** 2) + (dY ** 2))
		desiredDist = (desiredRightEyeX - self.desiredLeftEye[0])
		desiredDist *= self.desiredFaceWidth
		scale = desiredDist / dist

		# compute center (x, y)-coordinates (i.e., the median point)
		# between the two eyes in the input image
		eyesCenter = ((leftEyeCenter[0] + rightEyeCenter[0]) // 2,
			(leftEyeCenter[1] + rightEyeCenter[1]) // 2)

		# grab the rotation matrix for rotating and scaling the face
		M = cv2.getRotationMatrix2D(eyesCenter, angle, scale)

		# update the translation component of the matrix
		tX = self.desiredFaceWidth * 0.5
		tY = self.desiredFaceHeight * self.desiredLeftEye[1]
		M[0, 2] += (tX - eyesCenter[0])
		M[1, 2] += (tY - eyesCenter[1])

		# apply the affine transformation
		(w, h) = (self.desiredFaceWidth, self.desiredFaceHeight)
		output = cv2.warpAffine(image, M, (w, h),
			flags=cv2.INTER_CUBIC)

		# return the aligned face
		return output