1"""
2Extract form structure from a non-fillable PDF.
3 
4This script analyzes the PDF to find:
5- Text labels with their exact coordinates
6- Horizontal lines (row boundaries)
7- Checkboxes (small rectangles)
8 
9Output: A JSON file with the form structure that can be used to generate
10accurate field coordinates for filling.
11 
12Usage: python extract_form_structure.py <input.pdf> <output.json>
13"""
14 
15import json
16import sys
17import pdfplumber
18 
19 
20def extract_form_structure(pdf_path):
21    structure = {
22        "pages": [],
23        "labels": [],
24        "lines": [],
25        "checkboxes": [],
26        "row_boundaries": []
27    }
28 
29    with pdfplumber.open(pdf_path) as pdf:
30        for page_num, page in enumerate(pdf.pages, 1):
31            structure["pages"].append({
32                "page_number": page_num,
33                "width": float(page.width),
34                "height": float(page.height)
35            })
36 
37            words = page.extract_words()
38            for word in words:
39                structure["labels"].append({
40                    "page": page_num,
41                    "text": word["text"],
42                    "x0": round(float(word["x0"]), 1),
43                    "top": round(float(word["top"]), 1),
44                    "x1": round(float(word["x1"]), 1),
45                    "bottom": round(float(word["bottom"]), 1)
46                })
47 
48            for line in page.lines:
49                if abs(float(line["x1"]) - float(line["x0"])) > page.width * 0.5:
50                    structure["lines"].append({
51                        "page": page_num,
52                        "y": round(float(line["top"]), 1),
53                        "x0": round(float(line["x0"]), 1),
54                        "x1": round(float(line["x1"]), 1)
55                    })
56 
57            for rect in page.rects:
58                width = float(rect["x1"]) - float(rect["x0"])
59                height = float(rect["bottom"]) - float(rect["top"])
60                if 5 <= width <= 15 and 5 <= height <= 15 and abs(width - height) < 2:
61                    structure["checkboxes"].append({
62                        "page": page_num,
63                        "x0": round(float(rect["x0"]), 1),
64                        "top": round(float(rect["top"]), 1),
65                        "x1": round(float(rect["x1"]), 1),
66                        "bottom": round(float(rect["bottom"]), 1),
67                        "center_x": round((float(rect["x0"]) + float(rect["x1"])) / 2, 1),
68                        "center_y": round((float(rect["top"]) + float(rect["bottom"])) / 2, 1)
69                    })
70 
71    lines_by_page = {}
72    for line in structure["lines"]:
73        page = line["page"]
74        if page not in lines_by_page:
75            lines_by_page[page] = []
76        lines_by_page[page].append(line["y"])
77 
78    for page, y_coords in lines_by_page.items():
79        y_coords = sorted(set(y_coords))
80        for i in range(len(y_coords) - 1):
81            structure["row_boundaries"].append({
82                "page": page,
83                "row_top": y_coords[i],
84                "row_bottom": y_coords[i + 1],
85                "row_height": round(y_coords[i + 1] - y_coords[i], 1)
86            })
87 
88    return structure
89 
90 
91def main():
92    if len(sys.argv) != 3:
93        print("Usage: extract_form_structure.py <input.pdf> <output.json>")
94        sys.exit(1)
95 
96    pdf_path = sys.argv[1]
97    output_path = sys.argv[2]
98 
99    print(f"Extracting structure from {pdf_path}...")
100    structure = extract_form_structure(pdf_path)
101 
102    with open(output_path, "w") as f:
103        json.dump(structure, f, indent=2)
104 
105    print(f"Found:")
106    print(f"  - {len(structure['pages'])} pages")
107    print(f"  - {len(structure['labels'])} text labels")
108    print(f"  - {len(structure['lines'])} horizontal lines")
109    print(f"  - {len(structure['checkboxes'])} checkboxes")
110    print(f"  - {len(structure['row_boundaries'])} row boundaries")
111    print(f"Saved to {output_path}")
112 
113 
114if __name__ == "__main__":
115    main()
116