Landmark Index Dict Consistency

[duwudi]

The 5-landmark dict has a different indexing definition. This makes it difficult to write code that works with both the 5-landmark and 68-landmark dlib detectors.

For example, this:

left_eye_start, left_eye_end = FACIAL_LANDMARKS_68_IDXS["left_eye"]
left_eye_landmarks = features[left_eye_start:left_eye_end]

is not the same as this:

left_eye_start, left_eye_end = FACIAL_LANDMARKS_5_IDXS["left_eye"]
left_eye_landmarks = features[left_eye_start:left_eye_end]

The latter only gives one of the left eye landmark positions, rather than both as desired

[ritwikraha]

Hey @duwudi thanks for this, this is being looked into at https://github.com/PyImageSearch/imutils/pull/249