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| """Baseline operations — for text line baselines. | |
| A baseline is defined by a sequence of points, typically from left to right. | |
| """ | |
| from __future__ import annotations | |
| BaselinePoints = list[tuple[float, float]] | |
| def baseline_length(points: BaselinePoints) -> float: | |
| """Compute the total length of a baseline polyline.""" | |
| if len(points) < 2: | |
| return 0.0 | |
| total = 0.0 | |
| for i in range(len(points) - 1): | |
| dx = points[i + 1][0] - points[i][0] | |
| dy = points[i + 1][1] - points[i][1] | |
| total += (dx * dx + dy * dy) ** 0.5 | |
| return total | |
| def baseline_angle(points: BaselinePoints) -> float: | |
| """Compute the angle (in degrees) of a baseline from start to end. | |
| Returns 0.0 for a horizontal baseline, positive for downward slope. | |
| Returns 0.0 if the baseline has fewer than 2 points. | |
| """ | |
| if len(points) < 2: | |
| return 0.0 | |
| import math | |
| dx = points[-1][0] - points[0][0] | |
| dy = points[-1][1] - points[0][1] | |
| if dx == 0 and dy == 0: | |
| return 0.0 | |
| return math.degrees(math.atan2(dy, dx)) | |
| def interpolate_baseline(points: BaselinePoints, t: float) -> tuple[float, float]: | |
| """Interpolate a point along the baseline at parameter t in [0, 1]. | |
| t=0 returns the start, t=1 returns the end. | |
| For multi-segment baselines, t is proportional to total arc length. | |
| """ | |
| if len(points) < 2: | |
| if points: | |
| return points[0] | |
| raise ValueError("Cannot interpolate an empty baseline") | |
| t = max(0.0, min(1.0, t)) | |
| total_len = baseline_length(points) | |
| if total_len == 0: | |
| return points[0] | |
| target = t * total_len | |
| accumulated = 0.0 | |
| for i in range(len(points) - 1): | |
| dx = points[i + 1][0] - points[i][0] | |
| dy = points[i + 1][1] - points[i][1] | |
| seg_len = (dx * dx + dy * dy) ** 0.5 | |
| if accumulated + seg_len >= target: | |
| frac = (target - accumulated) / seg_len if seg_len > 0 else 0.0 | |
| return ( | |
| points[i][0] + frac * dx, | |
| points[i][1] + frac * dy, | |
| ) | |
| accumulated += seg_len | |
| return points[-1] | |