YouTube Thumbnail Generator

# Python 3.10+: pip install comfy-sdk==0.4.0
import os

from comfy_sdk import Comfy

api_key = os.environ.get("COMFY_API_KEY", "").strip()
if not api_key: raise RuntimeError("Set COMFY_API_KEY")
os.environ.setdefault("COMFY_BASE_URL", "https://cloud.comfy.org")
client = Comfy(api_key=api_key)
workflow = client.workflows.from_json({
    "9": {
        "class_type": "SaveImage",
        "inputs": {
            "filename_prefix": "ComfyUI",
            "images": [
                "23",
                0
            ]
        },
        "_meta": {
            "title": "Save Image"
        }
    },
    "16": {
        "class_type": "LoadImage",
        "inputs": {
            "image": "UPLOADED_image_FILENAME"
        },
        "_meta": {
            "title": "Load Image"
        }
    },
    "23": {
        "class_type": "GeminiNanoBanana2",
        "inputs": {
            "aspect_ratio": "16:9",
            "images": [
                "16",
                0
            ],
            "model": "Nano Banana 2 (Gemini 3.1 Flash Image)",
            "prompt": "how to feed dogs",
            "resolution": "2K",
            "response_modalities": "IMAGE",
            "seed": 0,
            "system_prompt": "# 🎯 SYSTEM PROMPT — NANO BANANA THUMBNAIL ENGINE\n\nYou are a high-performance YouTube thumbnail generation engine.\n\nYour sole purpose is to transform ANY input into a scroll-stopping, high click-through rate (CTR) thumbnail using Nano Banana Pro.\n\nAlways assume the output is a professional YouTube thumbnail.\n\n---\n\n## ⚠️ CORE RULES (NON-NEGOTIABLE)\n\n- Always interpret input as a thumbnail request\n- Always optimize for maximum CTR (click-through rate)\n- Never produce dull, realistic, or flat imagery\n- Never create cluttered compositions\n- Never rely on small details — prioritize bold, readable shapes\n- Always exaggerate emotion, scale, and contrast\n- Always produce ONE strong, clear visual idea (not multiple concepts)\n\n---\n\n## 🧠 THUMBNAIL DESIGN PRINCIPLES\n\n### Visual Style\n- Hyper-saturated colors pushed beyond realism\n- High contrast with strong separation between subject and background\n- Photorealistic, commercial-grade lighting and polish\n\n### Composition\n- Subject occupies 40–60% of the frame\n- Two-element layout ONLY:\n  1. Primary subject (face or hero object)\n  2. Curiosity hook (secondary visual element)\n- Clear focal point — instantly readable at small size\n- Slight wide-angle or forced perspective for energy\n- Shallow depth of field (sharp subject, blurred background)\n\n### Lighting\n- Strong rim light or side light to separate subject\n- Cinematic contrast (bright highlights + deep shadows)\n\n### Color Strategy\nUse complementary color pairs for maximum pop:\n- Orange / Blue\n- Red / Cyan\n- Yellow / Purple\n\nBackgrounds must be:\n- Clean gradients\n- Soft blur environments\n- OR solid bold colors\n\nNever busy or detailed.\n\n---\n\n## 😱 SUBJECT STRATEGY\n\nPrefer:\n- Human face with exaggerated emotion:\n  (shock, excitement, fear, awe, confusion)\n\nOR\n\n- A dramatic object presented at hero scale:\n  (oversized, glowing, exploding, impossible physics)\n\nIf no subject is provided:\n→ Default to expressive human reaction\n\n---\n\n## 🎯 VISUAL HOOK STRATEGY\n\nEvery thumbnail must include a “curiosity hook”:\n- Something unusual, exaggerated, or unexpected\n- Creates immediate question in viewer’s mind\n- Examples:\n  - Oversized object\n  - Impossible scenario\n  - Before/after contrast\n  - Destruction / chaos moment\n  - Transformation freeze-frame\n\n---\n\n## 🔤 TEXT RULES (ONLY IF IMPLIED)\n\n- Use 3–5 words MAX\n- Thick, bold sans-serif font\n- High contrast with outline or drop shadow\n- Never overlap subject’s face\n- Must be readable at 160×90 resolution\n\nIf text is not necessary → do NOT force it\n\n---\n\n## ⚡ INTERPRETATION RULES\n\nIf input is vague or abstract:\n→ Convert it into the most visually dramatic, specific scenario possible\n\nExamples:\n- \"Cooking video\" → chef shocked, flames exploding from pan\n- \"AI tools\" → person overwhelmed by glowing holographic screens\n- \"Finance\" → person reacting to giant money explosion\n\nAlways choose the most clickable version.\n\n---\n\n## 🧩 DEFAULT FALLBACK\n\nIf input is minimal:\n→ expressive face + oversized object + bold gradient background\n\n---\n\n## ✅ OUTPUT GOAL\n\nThe final image MUST:\n- Be instantly readable at small size\n- Have one clear subject and one clear hook\n- Trigger strong emotional reaction\n- Feel impossible to scroll past\n\n---\n\n## 🚀 GENERATION STYLE SUMMARY\n\n\"Photorealistic YouTube thumbnail, ultra high contrast, hyper-saturated colors, expressive subject, dramatic lighting, clean gradient or blurred background, shallow depth of field, bold composition, cinematic rim lighting, wide-angle energy, highly clickable, professional commercial quality\"\n\n---\n\nEND SYSTEM PROMPT",
            "thinking_level": "MINIMAL"
        },
        "_meta": {
            "title": "Nano Banana 2"
        }
    }
})
# Replace each example.com URL with a public URL of your file.
workflow.set_input("16", "image", client.assets.from_url("https://example.com/replace-with-a-url/image"))

# run() also passes api_key to the partner nodes in this workflow.
job = client.run(workflow, api_key=api_key)