Baseline

PreProcessing/scripts/process_characters.py

@@ -0,0 +1,264 @@
+from __future__ import annotations
+
+import argparse
+import html
+import os
+from pathlib import Path
+
+import cv2
+
+os.environ.setdefault(
+    "MPLCONFIGDIR",
+    str(Path(__file__).resolve().parents[1] / ".matplotlib-cache"),
+)
+
+import matplotlib
+
+matplotlib.use("Agg")
+
+import matplotlib.pyplot as plt
+import numpy as np
+
+
+IMAGE_SUFFIXES = {".png", ".jpg", ".jpeg", ".tif", ".tiff", ".bmp", ".webp"}
+
+
+def read_image(path: Path) -> np.ndarray:
+    raw = np.fromfile(str(path), dtype=np.uint8)
+    image = cv2.imdecode(raw, cv2.IMREAD_COLOR)
+    if image is None:
+        raise ValueError(f"Cannot read image: {path}")
+    return image
+
+
+def write_image(path: Path, image: np.ndarray) -> None:
+    ok, encoded = cv2.imencode(path.suffix, image)
+    if not ok:
+        raise ValueError(f"Cannot encode image: {path}")
+    encoded.tofile(str(path))
+
+
+def binarize_foreground(gray: np.ndarray) -> np.ndarray:
+    blurred = cv2.GaussianBlur(gray, (3, 3), 0)
+    threshold, _ = cv2.threshold(
+        blurred, 0, 255, cv2.THRESH_BINARY + cv2.THRESH_OTSU
+    )
+
+    border = np.concatenate(
+        [
+            gray[0, :],
+            gray[-1, :],
+            gray[:, 0],
+            gray[:, -1],
+        ]
+    )
+    background_is_light = np.median(border) >= 128
+
+    if background_is_light:
+        foreground = (gray < threshold).astype(np.uint8) * 255
+    else:
+        foreground = (gray > threshold).astype(np.uint8) * 255
+
+    return foreground
+
+
+def clean_mask(
+    mask: np.ndarray,
+    open_kernel_size: int,
+    close_kernel_size: int,
+    median_size: int,
+) -> np.ndarray:
+    if median_size > 1:
+        if median_size % 2 == 0:
+            median_size += 1
+        mask = cv2.medianBlur(mask, median_size)
+
+    open_kernel = cv2.getStructuringElement(
+        cv2.MORPH_RECT, (open_kernel_size, open_kernel_size)
+    )
+    opened = cv2.morphologyEx(mask, cv2.MORPH_OPEN, open_kernel)
+
+    close_kernel = cv2.getStructuringElement(
+        cv2.MORPH_RECT, (close_kernel_size, close_kernel_size)
+    )
+    return cv2.morphologyEx(opened, cv2.MORPH_CLOSE, close_kernel)
+
+
+def pixelate(mask: np.ndarray, factor: int) -> tuple[np.ndarray, np.ndarray]:
+    height, width = mask.shape
+    small_width = max(1, round(width / factor))
+    small_height = max(1, round(height / factor))
+    sampled = cv2.resize(
+        mask, (small_width, small_height), interpolation=cv2.INTER_AREA
+    )
+    small = np.where(sampled >= 96, 255, 0).astype(np.uint8)
+    large = cv2.resize(small, (width, height), interpolation=cv2.INTER_NEAREST)
+    return small, large
+
+
+def mask_to_display(mask: np.ndarray) -> np.ndarray:
+    return np.where(mask > 0, 0, 255).astype(np.uint8)
+
+
+def save_comparison(
+    path: Path,
+    original_bgr: np.ndarray,
+    cleaned_mask: np.ndarray,
+    pixelated_mask: np.ndarray,
+) -> None:
+    original_rgb = cv2.cvtColor(original_bgr, cv2.COLOR_BGR2RGB)
+    cleaned = mask_to_display(cleaned_mask)
+    pixelated = mask_to_display(pixelated_mask)
+
+    fig, axes = plt.subplots(1, 3, figsize=(12, 4), constrained_layout=True)
+    panels = [
+        ("Original", original_rgb, None),
+        ("Cleaned binary", cleaned, "gray"),
+        ("Pixelated", pixelated, "gray"),
+    ]
+
+    for axis, (title, image, cmap) in zip(axes, panels):
+        axis.imshow(image, cmap=cmap)
+        axis.set_title(title)
+        axis.axis("off")
+
+    fig.savefig(path, dpi=180)
+    plt.close(fig)
+
+
+def small_matrix_to_svg(
+    small_mask: np.ndarray,
+    original_width: int,
+    original_height: int,
+    title: str,
+) -> str:
+    rows, cols = small_mask.shape
+    cell_width = original_width / cols
+    cell_height = original_height / rows
+    escaped_title = html.escape(title)
+    parts = [
+        '<?xml version="1.0" encoding="UTF-8"?>',
+        (
+            f'<svg xmlns="http://www.w3.org/2000/svg" '
+            f'width="{original_width}" height="{original_height}" '
+            f'viewBox="0 0 {original_width} {original_height}" '
+            f'shape-rendering="crispEdges">'
+        ),
+        f"  <title>{escaped_title}</title>",
+        '  <rect width="100%" height="100%" fill="white"/>',
+        '  <g fill="black">',
+    ]
+
+    for row_index in range(rows):
+        col_index = 0
+        while col_index < cols:
+            if small_mask[row_index, col_index] == 0:
+                col_index += 1
+                continue
+
+            run_start = col_index
+            while col_index < cols and small_mask[row_index, col_index] > 0:
+                col_index += 1
+
+            x = run_start * cell_width
+            y = row_index * cell_height
+            width = (col_index - run_start) * cell_width
+            parts.append(
+                f'    <rect x="{x:.4f}" y="{y:.4f}" '
+                f'width="{width:.4f}" height="{cell_height:.4f}"/>'
+            )
+
+    parts.extend(["  </g>", "</svg>", ""])
+    return "\n".join(parts)
+
+
+def process_image(
+    image_path: Path,
+    processed_dir: Path,
+    comparison_dir: Path,
+    svg_dir: Path,
+    factor: int,
+    open_kernel_size: int,
+    close_kernel_size: int,
+    median_size: int,
+) -> None:
+    original = read_image(image_path)
+    gray = cv2.cvtColor(original, cv2.COLOR_BGR2GRAY)
+    binary = binarize_foreground(gray)
+    cleaned = clean_mask(
+        binary,
+        open_kernel_size=open_kernel_size,
+        close_kernel_size=close_kernel_size,
+        median_size=median_size,
+    )
+    small, pixelated = pixelate(cleaned, factor=factor)
+
+    stem = image_path.stem
+    write_image(processed_dir / f"{stem}_cleaned.png", mask_to_display(cleaned))
+    write_image(processed_dir / f"{stem}_pixelated.png", mask_to_display(pixelated))
+    save_comparison(
+        comparison_dir / f"{stem}_comparison.png", original, cleaned, pixelated
+    )
+
+    height, width = gray.shape
+    svg = small_matrix_to_svg(small, width, height, stem)
+    (svg_dir / f"{stem}_pixelated.svg").write_text(svg, encoding="utf-8")
+
+
+def main() -> None:
+    parser = argparse.ArgumentParser(
+        description="Clean, pixelate, and vectorize scanned seal-script characters."
+    )
+    parser.add_argument(
+        "--input-dir",
+        type=Path,
+        default=Path("PreProcessing/original_characters"),
+    )
+    parser.add_argument(
+        "--processed-dir",
+        type=Path,
+        default=Path("PreProcessing/processed_characters"),
+    )
+    parser.add_argument(
+        "--comparison-dir",
+        type=Path,
+        default=Path("PreProcessing/comparisons"),
+    )
+    parser.add_argument(
+        "--svg-dir",
+        type=Path,
+        default=Path("PreProcessing/svg_characters"),
+    )
+    parser.add_argument("--factor", type=int, default=15)
+    parser.add_argument("--open-kernel-size", type=int, default=2)
+    parser.add_argument("--close-kernel-size", type=int, default=3)
+    parser.add_argument("--median-size", type=int, default=5)
+    args = parser.parse_args()
+
+    for directory in (args.processed_dir, args.comparison_dir, args.svg_dir):
+        directory.mkdir(parents=True, exist_ok=True)
+
+    images = sorted(
+        path
+        for path in args.input_dir.iterdir()
+        if path.is_file() and path.suffix.lower() in IMAGE_SUFFIXES
+    )
+    if not images:
+        raise SystemExit(f"No images found in {args.input_dir}")
+
+    for image_path in images:
+        process_image(
+            image_path=image_path,
+            processed_dir=args.processed_dir,
+            comparison_dir=args.comparison_dir,
+            svg_dir=args.svg_dir,
+            factor=args.factor,
+            open_kernel_size=args.open_kernel_size,
+            close_kernel_size=args.close_kernel_size,
+            median_size=args.median_size,
+        )
+        print(f"processed: {image_path.name}")
+
+
+if __name__ == "__main__":
+    main()

PreProcessing/scripts/requirements.txt

@@ -0,0 +1,3 @@
+opencv-python-headless
+numpy
+matplotlib

PreProcessing/svg_characters/篆文字_page_017_text_17_pixelated.svg

@@ -0,0 +1,143 @@
+<?xml version="1.0" encoding="UTF-8"?>
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+  <title>篆文字_page_017_text_17</title>
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+  <g fill="black">
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