Merge pull request #59 from pelson/feature/ťkerning

Refine and add diacritics

Author: rgbkrk

xkcd-script/font/xkcd-script.otf

@@ -0,0 +1,112 @@
+# -*- coding: utf-8 -*-
+"""
+Extract hand-drawn glyphs from extras/ and convert them to SVG.
+
+Outputs go to ../generated/additional_chars/ and are consumed by pt6_derived_chars.py.
+"""
+import os
+import subprocess
+import tempfile
+import numpy as np
+from PIL import Image
+import fontforge
+
+OUT_DIR = '../generated/additional_chars'
+os.makedirs(OUT_DIR, exist_ok=True)
+
+UPSAMPLE = 12   # upscale factor before potrace; higher = more curve detail
+THRESHOLD = 160  # pixel value below which a pixel is considered ink
+
+
+def _clean_potrace_svg(raw_svg_path, clean_svg_path):
+    """Remove potrace artefacts from raw_svg_path and write clean_svg_path.
+
+    Potrace always emits a background rectangle covering the full canvas, plus
+    occasional single-pixel noise specks.  We load the SVG into FontForge,
+    drop those contours, and re-export so that pt6 receives a file containing
+    only the actual ink outlines.
+
+    Filtering rules (applied in order):
+      1. Background rectangle: <= 12 control points AND spans > 80% of the
+         full bounding box in both axes.
+      2. Noise specks: bbox smaller than 10% of the remaining ink extent in
+         both axes simultaneously.
+    """
+    scratch = fontforge.font()
+    g = scratch.createChar(-1, 'tmp')
+    g.importOutlines(raw_svg_path)
+
+    # Pass 1: drop background rectangle
+    full_bb = g.boundingBox()
+    full_w = full_bb[2] - full_bb[0]
+    full_h = full_bb[3] - full_bb[1]
+    pass1 = fontforge.layer()
+    for c in g.foreground:
+        cb = c.boundingBox()
+        span_w = (cb[2] - cb[0]) / full_w if full_w else 0
+        span_h = (cb[3] - cb[1]) / full_h if full_h else 0
+        if len(list(c)) <= 12 and span_w > 0.8 and span_h > 0.8:
+            continue
+        pass1 += c
+    g.foreground = pass1
+
+    # Pass 2: drop noise specks relative to ink extent
+    ink_bb = g.boundingBox()
+    ink_w = ink_bb[2] - ink_bb[0]
+    ink_h = ink_bb[3] - ink_bb[1]
+    ink = fontforge.layer()
+    for c in pass1:
+        cb = c.boundingBox()
+        if (cb[2] - cb[0]) < ink_w * 0.10 and (cb[3] - cb[1]) < ink_h * 0.10:
+            continue
+        ink += c
+    g.foreground = ink
+
+    scratch.save(clean_svg_path + '.sfd')  # FontForge can't export single-glyph SVG directly
+    # Export via generate — write to a temp SFD then export the glyph as SVG
+    g.export(clean_svg_path)
+    os.remove(clean_svg_path + '.sfd')
+
+
+def extract_symbol(arr, r0, r1, c0, c1, name):
+    """Crop glyph region, upsample, binarise, run potrace, clean, save SVG."""
+    crop = arr[r0:r1, c0:c1]
+    big = Image.fromarray(crop).resize(
+        (crop.shape[1] * UPSAMPLE, crop.shape[0] * UPSAMPLE),
+        Image.BILINEAR)
+    binary = (np.array(big) >= THRESHOLD).astype(np.uint8) * 255
+
+    with tempfile.TemporaryDirectory() as tmp:
+        png_path = os.path.join(tmp, f'{name}.png')
+        pbm_path = os.path.join(tmp, f'{name}.pbm')
+        raw_svg  = os.path.join(tmp, f'{name}_raw.svg')
+        Image.fromarray(binary, mode='L').save(png_path)
+        subprocess.check_call(['convert', png_path, '-threshold', '50%', pbm_path])
+        subprocess.check_call(['potrace', '-s', pbm_path, '-o', raw_svg])
+        svg_path = os.path.join(OUT_DIR, f'{name}.svg')
+        _clean_potrace_svg(raw_svg, svg_path)
+
+    print(f'  wrote {svg_path}')
+    return svg_path
+
+
+# ---------------------------------------------------------------------------
+# Hand-drawn extras (generator/extras/*.png)
+# Each file is a full-glyph image (no cropping needed).  RGBA images are
+# composited onto white before thresholding so transparent areas read as white.
+# A lower upsample factor is used since these images are already high-res.
+# ---------------------------------------------------------------------------
+
+EXTRAS_DIR = 'extras'
+
+EXTRAS = [
+    'eszett',   # ß U+00DF / ẞ U+1E9E source
+]
+
+print('Extracting hand-drawn extras...')
+for name in EXTRAS:
+    src_path = os.path.join(EXTRAS_DIR, f'{name}.png')
+    arr_extra = np.array(Image.open(src_path).convert('L'))
+    h, w = arr_extra.shape
+    extract_symbol(arr_extra, 0, h, 0, w, name)
+