Maxim Dolgolyov
78 lines
2.4 KiB
Python
78 lines
2.4 KiB
Python
"""
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Detect horizontal table borders in a scanned PDF page PNG
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and extract row bounding boxes.
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Usage:
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python detect_table_rows.py <page_png> [--min-width 0.7] [--debug]
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Prints detected row y-ranges as normalized (0-1) coordinates.
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"""
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import sys
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import argparse
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import numpy as np
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from PIL import Image
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def detect_rows(page_png, min_width_frac=0.7, debug=False):
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img = Image.open(page_png).convert('L') # grayscale
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arr = np.array(img)
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h, w = arr.shape
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# Binarize: dark pixels (potential lines) = True
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dark = arr < 128
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# Count dark pixels per row
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row_dark_count = dark.sum(axis=1)
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min_dark = int(min_width_frac * w)
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# Find rows that are mostly dark (horizontal lines)
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is_line = row_dark_count > min_dark
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# Group consecutive line pixels into bands
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line_bands = []
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in_band = False
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band_start = 0
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for y in range(h):
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if is_line[y] and not in_band:
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in_band = True
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band_start = y
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elif not is_line[y] and in_band:
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in_band = False
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band_end = y
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line_bands.append((band_start, band_end))
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if in_band:
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line_bands.append((band_start, h))
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if not line_bands:
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print("No table lines detected. Try reducing --min-width.", file=sys.stderr)
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return []
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# Extract row y-ranges between consecutive line bands
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rows = []
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for i in range(len(line_bands) - 1):
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y_top = line_bands[i][1] # bottom of upper border
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y_bot = line_bands[i + 1][0] # top of lower border
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if y_bot - y_top > 5: # skip tiny gaps
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rows.append((y_top / h, y_bot / h))
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if debug:
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print(f"Detected {len(line_bands)} line bands:")
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for b in line_bands:
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print(f" pixels {b[0]}-{b[1]} (y={b[0]/h:.3f}-{b[1]/h:.3f})")
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print(f"\nDetected {len(rows)} content rows:")
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for i, (y0, y1) in enumerate(rows):
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print(f" row {i}: y={y0:.3f}-{y1:.3f} (pixels {int(y0*h)}-{int(y1*h)}, height={int((y1-y0)*h)}px)")
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return rows
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if __name__ == '__main__':
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parser = argparse.ArgumentParser()
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parser.add_argument('page_png')
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parser.add_argument('--min-width', type=float, default=0.7)
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parser.add_argument('--debug', action='store_true')
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args = parser.parse_args()
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rows = detect_rows(args.page_png, min_width_frac=args.min_width, debug=args.debug)
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if not args.debug:
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for i, (y0, y1) in enumerate(rows):
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print(f"row {i}: {y0:.4f} - {y1:.4f}")
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