21d • 📘 Tutorials & Guides
Auto-Generated Thumbnails — Zero Canva
I stopped opening Canva for thumbnails about two months ago. Every thumbnail on my YouTube channel is now generated by a Python script. One command, ~10 seconds, done.
Here's the stack:
- Gemini generates the background image from a text prompt. Cinematic, saturated, 16:9. No stock photos, no searching, no licensing.
- Pillow (Python) handles the text overlay. Impact font at ~130px, thick black outline for readability on any background.
- Color-highlighted keywords draw the eye. You tag a word in the title and it renders in a different color with a glow effect behind it. The rest stays white.
- Vignette darkens the edges so the text pops in the center.
- Output: 1280x720, exactly what YouTube wants.
The whole thing runs from one command with a --title flag and an optional --subtitle. No templates, no layers, no drag-and-drop.
Why no face? I tested both. For the topics I cover (space/science Shorts, automation), faceless thumbnails with bold text and dramatic backgrounds perform the same or better. One less variable to manage.
What I learned building this:
1. Short punchy titles crush long question-format titles. "NEUTRON STARS COLLIDE" beats "What Happens When Neutron Stars Collide?" every time.
2. The Gemini prompt matters. Adding "do NOT include any text in the image" prevents the AI from baking words into the background — which ruins the overlay.
3. Thick outlines are non-negotiable. Without them, white text disappears on bright backgrounds. The script draws the outline pixel by pixel in a radius around each character.
The script also supports an avatar cutout mode (face extracted with rembg, composited with a drop shadow) but I keep it off for my content.
Total cost: $0. Gemini API is free tier. Pillow is open source. The only investment was writing the script.
Want the exact Python script and setup instructions? Comment below or DM me and I'll send them over.
More on automating content pipelines: https://kjetilfuras.com/blog-automation/
0
0 comments
Auto-Generated Thumbnails — Zero Canva
skool.com/build-automate
Build autonomous AI agents with Claude Code & OpenClaw. Real configs, build logs, and a practitioner community that actually ships.
Powered by