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| from math import sqrt | |
| TRIANGLE_WEIGHTS = 0x1 | |
| GAUSSIAN_WEIGHTS = 0x2 | |
| weight_makers = {TRIANGLE_WEIGHTS:lambda hist_len : range(1, hist_len + 1)} | |
| fixation_thresh_min_mm = 20 | |
| fixation_thresh_max_mm = 40 | |
| class GazeSmoother: | |
| def __init__(self, hist_len, weight_type=TRIANGLE_WEIGHTS): | |
| self.weights = weight_makers[weight_type](hist_len) | |
| self.weights = [w / float(sum(self.weights)) for w in self.weights] | |
| self.gaze_histories = [ [(0, 0)] * hist_len, [(0, 0)] * hist_len ] | |
| def remove_inaccurate_pts_on_fixation(self, gaze_pts): | |
| """ Detects if gaze is fixed then removes inaccurate gaze points | |
| """ | |
| weighted_gaze_dists = {} | |
| gaze_is_fixed = False | |
| # determine if gazed is fixed by comparing current gaze points to their history | |
| for i, gaze_pt in enumerate(gaze_pts): | |
| if gaze_pt is not None: | |
| gaze_dists = [ sqrt((x - gaze_pt[0]) ** 2 + (y - gaze_pt[1]) ** 2) for (x, y) in self.gaze_histories[i]] | |
| zipped = zip(self.weights, gaze_dists) | |
| weighted_gaze_dists[gaze_pt] = reduce(lambda (w1, d1), (w2, d2) : (1, (w1 * d1 + w2 * d2)), zipped)[1] | |
| gaze_is_fixed = (weighted_gaze_dists[gaze_pt] < fixation_thresh_min_mm) | |
| # Filter out gaze points that differ wildly from their histories if gaze is fixed | |
| if gaze_is_fixed: | |
| return [None if (g is None or weighted_gaze_dists[g] > fixation_thresh_max_mm) else g for g in gaze_pts] | |
| else: | |
| return gaze_pts | |
| def update_gaze_history(self, gaze_pts): | |
| for i, gaze_pt in enumerate(gaze_pts): | |
| if gaze_pt is not None: | |
| self.gaze_histories[i].append(gaze_pt) | |
| self.gaze_histories[i] = self.gaze_histories[i][-len(self.weights):] | |
| def smooth_gaze(self, gaze_pts): | |
| gaze_pts = self.remove_inaccurate_pts_on_fixation(gaze_pts) | |
| self.update_gaze_history(gaze_pts) | |
| smoothed_pts = [] | |
| for i in range(2): # Find smoothed gaze for each eye | |
| zipped = zip(self.weights, self.gaze_histories[i]) # has form [(1,(x,y)),(2,(x,y)),(3,(x,y))...] | |
| smoothed_pts.append(reduce(lambda (w1, (x1, y1)), (w2, (x2, y2)) : # now reduce to (1, smoothed_pt) for each eye | |
| (1, (w1 * x1 + w2 * x2, w1 * y1 + w2 * y2)), | |
| zipped)[1]) # only want last part of (w,(x,y)) | |
| xs, ys = [x for (x, _) in smoothed_pts], [y for (_, y) in smoothed_pts] | |
| return sum(xs) / len(xs), sum(ys) / len(ys) # return averaged gaze point | |