# Reconstructs assets/SingeText.jpeg as assets/SingeText.svg:  thresholds the logotype, traces it
# with potrace into Bezier outlines, and writes a tightly cropped SVG with a transparent background.
# Usage:  python3 util/traceText.py assets/SingeText.jpeg assets/SingeText.svg [potrace] [check.svg]
# Needs Pillow and potrace (https://potrace.sourceforge.net).  check.svg keeps the full page so it
# can be rendered over the original for comparison.
import os
import re
import subprocess
import sys
import tempfile
from PIL import Image, ImageFilter

src = sys.argv[1]
out = sys.argv[2]
potrace = sys.argv[3] if len(sys.argv) > 3 else 'potrace'
check = sys.argv[4] if len(sys.argv) > 4 else None

# Trace at 4x so the anti-aliased edges of the JPEG turn into smooth curves rather than steps.
scale = 4
BLUR = 3.5
grey = Image.open(src).convert('L')
w, h = grey.size
big = grey.resize((w * scale, h * scale), Image.LANCZOS)
# A light blur removes JPEG ringing along the edges, which would otherwise trace as tiny wobbles.
big = big.filter(ImageFilter.GaussianBlur(BLUR))
mono = big.point(lambda v: 255 if v >= 128 else 0).convert('1')

work = tempfile.mkdtemp()
pbm = os.path.join(work, 'text.pbm')
mono.save(pbm)

def trace(tight):
    args = [potrace, pbm, '-s', '--flat', '-a', '1.0', '-O', '0.2', '-u', '1', '-t', str(4 * scale * scale), '-o', '-']
    if tight:
        args.append('--tight')
    svg = subprocess.run(args, check=True, capture_output=True, text=True).stdout
    width = float(re.search(r'width="([\d.]+)pt"', svg).group(1))
    height = float(re.search(r'height="([\d.]+)pt"', svg).group(1))
    transform = re.search(r'transform="([^"]+)"', svg).group(1)
    path = re.search(r'<path[^>]*\bd="([^"]+)"', svg, re.S).group(1)
    path = re.sub(r'\s+', ' ', path).strip()
    return width, height, transform, path

def write(name, tight):
    width, height, transform, path = trace(tight)
    lines = ['<?xml version="1.0" encoding="UTF-8"?>',
             '<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 %.2f %.2f" width="%.2f" height="%.2f">' % (width / scale, height / scale, width / scale, height / scale),
             '  <!-- Singe logotype, traced from SingeText.jpeg; transparent background. -->',
             '  <title>Singe</title>',
             '  <g transform="scale(%g) %s" fill="#000" stroke="none">' % (1.0 / scale, transform),
             '    <path d="%s"/>' % path,
             '  </g>',
             '</svg>']
    open(name, 'w').write('\n'.join(lines) + '\n')
    print('%s: %.0fx%.0f, %d bytes' % (name, width / scale, height / scale, os.path.getsize(name)))

write(out, True)
if check:
    write(check, False)