85 lines
2.4 KiB
Python
85 lines
2.4 KiB
Python
"""Reading face crops off a source video.
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Shared by the dataset adapters that pack from video rather than from
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pre-extracted frames.
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"""
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import cv2
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import numpy as np
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def crop_face(frame, bbox, gray=True, dim=(112, 112)):
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if bbox is None:
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return np.full(dim if gray else (dim[1], dim[0], 3), 128, dtype=np.uint8)
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x1, y1, x2, y2 = int(bbox[0]), int(bbox[1]), int(bbox[2]), int(bbox[3])
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if x1 >= x2 or y1 >= y2:
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return np.full(dim if gray else (dim[1], dim[0], 3), 128, dtype=np.uint8)
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h, w = frame.shape[:2]
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cx, cy = (x1 + x2) // 2, (y1 + y2) // 2
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size = max(x2 - x1, y2 - y1)
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half = size // 2
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x1s, y1s = cx - half, cy - half
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x2s, y2s = x1s + size, y1s + size
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x1c, y1c = max(0, x1s), max(0, y1s)
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x2c, y2c = min(w, x2s), min(h, y2s)
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if x1c >= x2c or y1c >= y2c:
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return np.full(dim if gray else (dim[1], dim[0], 3), 128, dtype=np.uint8)
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cropped = frame[y1c:y2c, x1c:x2c]
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if gray:
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cropped = cv2.cvtColor(cropped, cv2.COLOR_BGR2GRAY)
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border_val = 128
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else:
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cropped = cv2.cvtColor(cropped, cv2.COLOR_BGR2RGB)
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border_val = (128, 128, 128)
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pad_top, pad_left = y1c - y1s, x1c - x1s
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pad_bottom, pad_right = y2s - y2c, x2s - x2c
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if pad_top > 0 or pad_bottom > 0 or pad_left > 0 or pad_right > 0:
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cropped = cv2.copyMakeBorder(
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cropped,
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pad_top,
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pad_bottom,
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pad_left,
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pad_right,
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cv2.BORDER_CONSTANT,
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value=border_val,
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)
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return cv2.resize(cropped, dim)
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def load_visual(video_path, start_frame=0, target_frames=None):
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"""Decode a native-FPS video interval without changing its timeline."""
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if start_frame < 0:
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raise ValueError("start_frame cannot be negative")
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if target_frames is not None and target_frames < 0:
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raise ValueError("target_frames cannot be negative")
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cap = cv2.VideoCapture(str(video_path))
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if not cap.isOpened():
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raise FileNotFoundError(f"could not open video: {video_path}")
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fps = float(cap.get(cv2.CAP_PROP_FPS))
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if fps <= 0:
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cap.release()
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raise ValueError(f"video has an invalid frame rate: {video_path}")
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cap.set(cv2.CAP_PROP_POS_FRAMES, start_frame)
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frames = []
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while target_frames is None or len(frames) < target_frames:
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ok, frame = cap.read()
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if not ok:
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break
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frames.append(frame)
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cap.release()
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return frames, fps
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