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#!/usr/bin/env python
from dataclasses import dataclass, field
import math
from argaze import GazeFeatures
import numpy
@dataclass(frozen=True)
class Fixation(GazeFeatures.Fixation):
"""Define dispersion based fixation."""
dispersion: float = field(init=False)
"""Dispersion of all gaze positions belonging to the fixation."""
euclidian: bool = field(default=True)
"""Does the distance is calculated in euclidian way."""
centroid: tuple = field(init=False)
"""Centroïd of all gaze positions belonging to the fixation."""
def __post_init__(self):
super().__post_init__()
x_list = [gp[0] for (ts, gp) in list(self.positions.items())]
y_list = [gp[1] for (ts, gp) in list(self.positions.items())]
cx = numpy.mean(x_list)
cy = numpy.mean(y_list)
# Select dispersion algorithm
if self.euclidian:
c = [cx, cy]
points = numpy.column_stack([x_list, y_list])
dist = (points - c)**2
dist = numpy.sum(dist, axis=1)
dist = numpy.sqrt(dist)
__dispersion = max(dist)
else:
__dispersion = (max(x_list) - min(x_list)) + (max(y_list) - min(y_list))
# Update frozen dispersion attribute
object.__setattr__(self, 'dispersion', __dispersion)
# Update frozen centroid attribute
object.__setattr__(self, 'centroid', (cx, cy))
@dataclass(frozen=True)
class Saccade(GazeFeatures.Saccade):
"""Define dispersion based saccade."""
def __post_init__(self):
super().__post_init__()
@dataclass
class GazeMovementIdentifier(GazeFeatures.GazeMovementIdentifier):
"""Implementation of the I-DT algorithm as described in:
Dario D. Salvucci and Joseph H. Goldberg. 2000. Identifying fixations and
saccades in eye-tracking protocols. In Proceedings of the 2000 symposium
on Eye tracking research & applications (ETRA '00). ACM, New York, NY, USA,
71-78. [DOI=http://dx.doi.org/10.1145/355017.355028](DOI=http://dx.doi.org/10.1145/355017.355028)
"""
dispersion_threshold: int|float
"""Maximal distance allowed to consider several gaze positions as a fixation."""
duration_threshold: int|float
"""Minimal duration allowed to consider several gaze positions as a fixation."""
def __iter__(self) -> GazeFeatures.GazeMovementType:
"""GazeMovement identification generator."""
self.__last_fixation = None
# while there are 2 gaze positions at least
while len(self.__ts_gaze_positions) >= 2:
# copy remaining timestamped gaze positions
remaining_ts_gaze_positions = self.__ts_gaze_positions.copy()
# select timestamped gaze position until a duration threshold
ts_start, gaze_position_start = remaining_ts_gaze_positions.pop_first()
# Ignore non valid start position
if not gaze_position_start.valid:
self.__ts_gaze_positions.pop_first()
continue
ts_gaze_positions = GazeFeatures.TimeStampedGazePositions()
ts_gaze_positions[ts_start] = gaze_position_start
# Select next position
ts_next, gaze_position_next = remaining_ts_gaze_positions.first
while (ts_next - ts_start) < self.duration_threshold:
# Ignore non valid position
# Should we consider invalid position to not break fixation ?
if gaze_position_next.valid:
# Store selected position
ts, gaze_position = remaining_ts_gaze_positions.pop_first()
ts_gaze_positions[ts] = gaze_position
else:
remaining_ts_gaze_positions.pop_first()
try:
# Read next position
ts_next, gaze_position_next = remaining_ts_gaze_positions.first
except:
break
# is it a new fixation ?
new_fixation = Fixation(ts_gaze_positions)
# dispersion is small : extending fixation
if new_fixation.dispersion <= self.dispersion_threshold:
# remove selected gaze positions
for gp in ts_gaze_positions:
self.__ts_gaze_positions.pop_first()
# extend fixation position from a copy
ts_gaze_positions_extension = ts_gaze_positions.copy()
# are next gaze positions not too dispersed ?
while len(remaining_ts_gaze_positions) > 0:
# Select next gaze position
ts_next, gaze_position_next = remaining_ts_gaze_positions.first
# Ignore non valid position
# Should we consider invalid position to not break fixation ?
if not gaze_position_next.valid:
remaining_ts_gaze_positions.pop_first()
continue
ts_gaze_positions_extension[ts_next] = gaze_position_next
# how much gaze is dispersed ?
extended_fixation = Fixation(ts_gaze_positions_extension)
# dispersion becomes too wide : ignore extended fixation
if extended_fixation.dispersion > self.dispersion_threshold:
break
# update new fixation
new_fixation = Fixation(ts_gaze_positions_extension.copy())
# remove selected gaze position
remaining_ts_gaze_positions.pop_first()
self.__ts_gaze_positions.pop_first()
# is the new fixation have a duration ?
if new_fixation.duration > 0:
if self.__last_fixation != None:
# store start and end positions in a timestamped buffer
ts_saccade_positions = GazeFeatures.TimeStampedGazePositions()
start_position_ts, start_position = self.__last_fixation.positions.last
ts_saccade_positions[start_position_ts] = start_position
end_position_ts, end_position = new_fixation.positions.first
ts_saccade_positions[end_position_ts] = end_position
if end_position_ts > start_position_ts:
new_saccade = Saccade(ts_saccade_positions)
yield new_saccade
self.__last_fixation = new_fixation
yield new_fixation
# dispersion too wide : consider next gaze position
else:
self.__ts_gaze_positions.pop_first()
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