2021 1101 A failed experiment: Python Pillow and a Cistercian font

#!/usr/bin/env python3

import argparse
import datetime
import logging
import math
import os
import pathlib
import pdb
import sys
import traceback
import typing

import yaml

from PIL import Image, ImageDraw, ImageFilter, ImageFont
from PIL.ImageOps import exif_transpose

logging.basicConfig(
    level=logging.INFO, format="[%(asctime)s] [%(name)s] [%(levelname)s] %(message)s"
)
logger = logging.getLogger(__name__)


def idb_excepthook(type, value, tb):
    """Call an interactive debugger in post-mortem mode

    If you do "sys.excepthook = idb_excepthook", then an interactive debugger
    will be spawned at an unhandled exception
    """
    if hasattr(sys, "ps1") or not sys.stderr.isatty():
        sys.__excepthook__(type, value, tb)
    else:
        traceback.print_exception(type, value, tb)
        print
        pdb.pm()


def resolvepath(path):
    return os.path.realpath(os.path.normpath(os.path.expanduser(path)))


def find_first_image(path):
    """Find the first image under a path"""
    path = pathlib.PurePath(path)
    for f in sorted(os.listdir(path)):
        purepath = pathlib.PurePath(path, f)
        print(purepath)
        if not os.path.isfile(purepath):
            continue
        if purepath.suffix.lower() in [".jpeg", ".jpg", ".png"]:
            return purepath
    raise Exception(f"No image found in {path}")


def dumbparse_frontmatter(post_md: str):
    """Parse metadata from a post Markdown file with YAML frontmatter

    This is a very dumb way to do it but whatever
    """
    with open(post_md) as postfp:
        contents = postfp.read().split("\n")
    if contents[0] != "---":
        raise Exception(f"No YAML metadata in post file {postfp}")
    closing_dashes = contents[1:].index("---")
    frontmatter_yml = "\n".join(contents[1 : closing_dashes + 1])
    frontmatter = yaml.load(frontmatter_yml, yaml.Loader)
    return {
        "title": frontmatter["title"],
        "date": frontmatter["date"],
    }


def int2cistercian(num: int):
    """Return Unicdoe codepoints for FRBCistercian given a 4 digit int

    FRBCistercian uses the Private Use Area of Unicode.
    To get the right glyph, we have to map to this area.
    <https://github.com/ctrlcctrlv/FRBCistercian/blob/main/codepoints.tsv>
    """

    def get_digit(num: int, power: int):
        """Get the digit of a power.

        E.g:
            num(456, 1) returns 6, which is in the ones place.
            num(456, 2) returns 5, which is in the tens place
        """
        return math.floor((num / pow(10, power)) % 10)

    def kthu(num: int):
        """Return an array of digits representing places in a 1-4 digit number

        [thousands, hundreds, tens, ones] also called KTHU
        """
        if num < 0 or num > 9999:
            raise Exception("kthu() only supports numbers between 0-9999 (inclusive)")
        return [
            get_digit(num, 3),
            get_digit(num, 2),
            get_digit(num, 1),
            get_digit(num, 0),
        ]

    digits = kthu(num)
    result = [0x100002]
    if digits[0] > 0:
        result += [0x10001E + digits[0] - 1]
    if digits[1] > 0:
        result += [0x100015 + digits[1] - 1]
    if digits[2] > 0:
        result += [0x10000C + digits[2] - 1]
    if digits[3] > 0:
        # We do not subtract 1 because there is a zero,
        # but there is no "zero ten " / "zero hundred" / "zero thousand".
        result += [0x100002 + digits[3]]

    return "".join([chr(b) for b in result])


def date2cistercian(dt: datetime.datetime):
    """Convert a datetime to three Cistercian glyphs

    These glyphs represent the year, the month/day, and the hour/minute
    """
    yyyy = int(dt.strftime("%Y"))
    mmdd = int(dt.strftime("%m%d"))
    hhmm = int(dt.strftime("%H%M"))
    # print(f"Building Cistercian datestamp for {yyyy} {mmdd} {hhmm}")
    cyyyy = int2cistercian(yyyy)
    cmmdd = int2cistercian(mmdd)
    chhmm = int2cistercian(hhmm)
    cdate = f"{cyyyy} {cmmdd} {chhmm}"
    # print(f"Year codepoints: {[ord(c) for c in cyyyy]}")
    # with open("cdate.txt", "wt") as cdfp:
    #     cdfp.write(cdate)
    return cdate


def generate_ogimage(
    srcimgpath: str,
    outpng: str,
    date: datetime.datetime,
    title: str,
    text_font_path: str = "themes/qualia/static/fonts/Roboto/Roboto-Bold.ttf",
    cistercian_font_path: str = "themes/qualia/static/fonts/FRBCistercian.otf",
    outwidth: int = 800,
):
    """Generate a PNG suitable for an og:image

    Generates a Cistercian datestamp
    """

    with open(srcimgpath, "rb") as imgfp:
        img = Image.open(imgfp)
        print(f"Raw image size: {img.size}")

        # Fucking EXIF tags
        # This both removes EXIF rotation tags and returns a rotated image
        img = exif_transpose(img)
        print(f"EXIF-Transposed image size: {img.size}")

        # First, resize the image to be outwidth
        if img.size[0] > outwidth:
            outheight = int(outwidth * img.size[1] / img.size[0])
            img = img.resize((outwidth, outheight))
            print(f"Resized image size: {img.size}")

        # Going for a 1.91:1 aspect ratio with set width
        # TODO: If the image is lower height than the calculated new_height,
        # the result is probably wrong
        new_height = int(outwidth / 1.91)
        crop = {
            "left": 0,
            "right": outwidth,
            "top": int((img.size[1] / 2) - (new_height / 2)),
            "bottom": int((img.size[1] / 2) + (new_height / 2)),
        }
        img = img.crop((crop["left"], crop["top"], crop["right"], crop["bottom"]))
        print(f"Cropped image size: {img.size}")

        img = img.filter(ImageFilter.GaussianBlur(3))

        x_center = int(outwidth / 2)
        y_center = int(new_height / 2)

        titlefont = ImageFont.truetype(text_font_path, 64)
        titledraw = ImageDraw.Draw(img)
        titledraw.text((20, 20), title, (0, 0, 0), font=titlefont)

        cistercianfont = ImageFont.truetype(cistercian_font_path, 64)
        cisterciandraw = ImageDraw.Draw(img)
        cisterciandraw.text(
            (20, y_center), date2cistercian(date), (0, 0, 0), font=cistercianfont
        )

        img.save(outpng)

    return


def parseargs(arguments: typing.List[str]):
    """Parse program arguments"""
    parser = argparse.ArgumentParser(description="Generate og:image for a post")
    parser.add_argument(
        "--debug",
        "-d",
        action="store_true",
        help="Launch a debugger on unhandled exception",
    )
    parser.add_argument(
        "post",
        help="Path to the post directory, like content/blog/example-post; expected to have an index.md and at least one image file",
    )
    parser.add_argument(
        "outfile", help="Path to the output file, which should be a PNG"
    )
    parsed = parser.parse_args(arguments)
    return parsed


def main(*arguments):
    """Main program"""
    parsed = parseargs(arguments[1:])
    if parsed.debug:
        sys.excepthook = idb_excepthook
    frontmatter = dumbparse_frontmatter(os.path.join(parsed.post, "index.md"))
    firstimg = find_first_image(parsed.post)
    outfile = resolvepath(parsed.outfile)
    generate_ogimage(firstimg, outfile, frontmatter["date"], frontmatter["title"])
    print(f"Generated image at {outfile}")


if __name__ == "__main__":
    sys.exit(main(*sys.argv))