gen_cover.py

#!/usr/bin/env python3
"""Generate the book cover image with an image-generation model.

This is, fittingly, the book eating its own dog food: the cover of a book about
AI agents is produced by calling an image-generation model. Run it once; the
cover (cover.tex) automatically switches to images/cover-image.png when present
— no other change needed. You can then note on the colophon that the cover was
generated by AI.

Usage (OpenAI, the default):
    pip install openai
    export OPENAI_API_KEY=sk-...
    python gen_cover.py
"""
import os

# ── The prompt ────────────────────────────────────────────────────────────
PROMPT = (
    "Vintage scientific engraving illustration of an octopus, in the classic style of "
    "19th-century natural-history woodcuts and the O'Reilly animal book covers. Finely "
    "detailed black pen-and-ink crosshatching and fine line work; pure black line art, "
    "no color, no gray wash, no shading fills. The whole octopus rendered elegantly with "
    "gracefully curling tentacles, anatomically believable, slightly stylized. Perfectly "
    "clean pure white background, no scenery, no frame, no border, no text, no lettering, "
    "no numbers. Centered composition, crisp, high detail."
)

OUT = os.path.join(os.path.dirname(os.path.abspath(__file__)), "images", "cover-image.png")


def generate_openai(prompt, out):
    """OpenAI Images API. Uses gpt-image-1 if available, else dall-e-3."""
    api_key = os.environ.get("OPENAI_API_KEY")
    if not api_key:
        print("OPENAI_API_KEY environment variable not set. Skipping API image generation.")
        print("Cover page will use default TikZ vector art in cover.tex.")
        return False
    from openai import OpenAI
    import base64, urllib.parse, urllib.request
    client = OpenAI()
    try:
        r = client.images.generate(model="gpt-image-1", prompt=prompt,
                                    size="1024x1536", quality="high", n=1)
        data = base64.b64decode(r.data[0].b64_json)
        with open(out, "wb") as f:
            f.write(data)
        return True
    except Exception as e:
        print(f"gpt-image-1 unavailable ({e}); falling back to dall-e-3 …")
        try:
            r = client.images.generate(model="dall-e-3", prompt=prompt,
                                        size="1024x1792", quality="hd",
                                        style="natural", n=1)
            url = r.data[0].url
            parsed = urllib.parse.urlparse(url)
            if parsed.scheme != "https" or not parsed.netloc:
                raise ValueError(f"Invalid URL scheme or host for image download: {url}")
            with urllib.request.urlopen(url, timeout=60) as resp:
                with open(out, "wb") as f:
                    f.write(resp.read())
            return True
        except Exception as fallback_err:
            print(f"dall-e-3 image generation failed ({fallback_err}). Falling back to default TikZ art in cover.tex.")
            return False


def generate(prompt, out):
    return generate_openai(prompt, out)


if __name__ == "__main__":
    os.makedirs(os.path.dirname(OUT), exist_ok=True)
    print("Generating cover image …")
    if generate(PROMPT, OUT):
        print(f"Saved {OUT}")
    print("Now rebuild:  bash build_pdf.sh   (cover.tex auto-detects the image)")