180 lines
6.0 KiB
Python
180 lines
6.0 KiB
Python
#!/usr/bin/env python3
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"""
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Converts bounding box coordinates from image coordinates to PDF coordinates.
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This script takes a .scan.json file (with image coordinates) and converts all
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bounding boxes to PDF coordinates, producing a .form.json file.
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Image coordinates: Origin at top-left, Y increases downward
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PDF coordinates: Origin at bottom-left, Y increases upward
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Usage:
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python convert_coordinates.py <scan.json> <pdf_file>
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"""
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import json
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import sys
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from pathlib import Path
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from PIL import Image
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from pypdf import PdfReader
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def image_to_pdf_coords(image_bbox, image_width, image_height, pdf_width, pdf_height):
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"""
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Convert bounding box from image coordinates to PDF coordinates.
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Args:
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image_bbox: [x1, y1, x2, y2] in image coordinates (top-left origin)
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image_width: Width of the image in pixels
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image_height: Height of the image in pixels
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pdf_width: Width of the PDF page in points
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pdf_height: Height of the PDF page in points
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Returns:
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[x1, y1, x2, y2] in PDF coordinates (bottom-left origin)
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"""
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x_scale = pdf_width / image_width
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y_scale = pdf_height / image_height
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# Convert X coordinates (simple scaling, same origin)
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pdf_x1 = image_bbox[0] * x_scale
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pdf_x2 = image_bbox[2] * x_scale
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# Convert Y coordinates (flip vertical axis)
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# Image: y1 is top, y2 is bottom (y1 < y2 in image coords)
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# PDF: need to flip - what's at top of image is high Y in PDF
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pdf_y1 = (image_height - image_bbox[3]) * y_scale # Bottom in PDF (was bottom in image)
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pdf_y2 = (image_height - image_bbox[1]) * y_scale # Top in PDF (was top in image)
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return [pdf_x1, pdf_y1, pdf_x2, pdf_y2]
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def get_image_dimensions(images_dir, page_number):
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"""Get dimensions of the PNG image for a specific page."""
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image_path = Path(images_dir) / f"page_{page_number}.png"
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if not image_path.exists():
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raise FileNotFoundError(f"Image not found: {image_path}")
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with Image.open(image_path) as img:
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return img.width, img.height
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def convert_scan_to_form(scan_json_path, pdf_path, output_json_path):
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"""
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Convert .scan.json (image coords) to .form.json (PDF coords).
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Args:
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scan_json_path: Path to input .scan.json file
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pdf_path: Path to the PDF file
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output_json_path: Path to output .form.json file
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"""
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# Load scan data
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with open(scan_json_path, 'r') as f:
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fields = json.load(f)
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# Get PDF dimensions
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reader = PdfReader(pdf_path)
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# Determine images directory (same directory as scan.json)
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scan_path = Path(scan_json_path)
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images_dir = scan_path.parent
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if not images_dir.exists():
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raise FileNotFoundError(
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f"Images directory not found: {images_dir}\n"
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f"Expected to find page images in {images_dir}"
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)
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# Convert each field
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converted_fields = []
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for field in fields:
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page_num = field.get('page', 1)
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# Get dimensions for this page
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page = reader.pages[page_num - 1] # Convert to 0-indexed
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pdf_width = float(page.mediabox.width)
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pdf_height = float(page.mediabox.height)
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image_width, image_height = get_image_dimensions(images_dir, page_num)
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# Create converted field
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converted_field = field.copy()
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# Convert main rect
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if 'rect' in field:
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converted_field['rect'] = image_to_pdf_coords(
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field['rect'],
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image_width, image_height,
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pdf_width, pdf_height
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)
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# Convert label_rect if present
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if 'label_rect' in field:
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converted_field['label_rect'] = image_to_pdf_coords(
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field['label_rect'],
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image_width, image_height,
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pdf_width, pdf_height
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)
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# Convert radio button options if present
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if 'radio_options' in field:
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converted_options = []
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for option in field['radio_options']:
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converted_option = option.copy()
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if 'rect' in option:
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converted_option['rect'] = image_to_pdf_coords(
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option['rect'],
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image_width, image_height,
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pdf_width, pdf_height
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)
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converted_options.append(converted_option)
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converted_field['radio_options'] = converted_options
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converted_fields.append(converted_field)
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# Write output
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with open(output_json_path, 'w') as f:
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json.dump(converted_fields, f, indent=2)
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print(f"Converted {len(converted_fields)} fields from image to PDF coordinates")
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print(f"Input: {scan_json_path}")
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print(f"Output: {output_json_path}")
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# Show an example conversion
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if converted_fields:
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print("\nExample conversion (first field):")
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orig = fields[0]
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conv = converted_fields[0]
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print(f" Field: {orig.get('field_id')}")
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print(f" Image rect: {orig.get('rect')}")
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print(f" PDF rect: {conv.get('rect')}")
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if __name__ == "__main__":
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if len(sys.argv) != 3:
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print("Usage: convert_coordinates.py <scan.json> <pdf_file>")
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print()
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print("Example:")
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print(" python convert_coordinates.py my_form.chatfield/my_form.scan.json my_form.pdf")
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print()
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print("Output filename is automatically computed by replacing .scan.json with .form.json")
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sys.exit(1)
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scan_json_path = sys.argv[1]
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pdf_path = sys.argv[2]
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# Compute output filename by replacing .scan.json with .form.json
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scan_path = Path(scan_json_path)
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if not scan_path.name.endswith('.scan.json'):
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print(f"Error: Input file must end with .scan.json, got: {scan_path.name}", file=sys.stderr)
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sys.exit(1)
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output_json_path = str(scan_path.parent / scan_path.name.replace('.scan.json', '.form.json'))
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try:
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convert_scan_to_form(scan_json_path, pdf_path, output_json_path)
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except Exception as e:
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print(f"Error: {e}", file=sys.stderr)
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sys.exit(1)
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