FradSer Generate Image (gemini / openai backends)
Turn a text prompt — optionally with reference images — into one or more images
via one of two explicit backends. --backend has no default — always pick
one (gemini or openai), or set IMAGE_BACKEND. The script does the API
call, file saving, and configuration; your job is to pick the backend, craft a
strong prompt, and wire up the flags.
gemini— Google's native Gemini API viagoogle-genai. Full feature set:--aspect-ratio,--sizetiers (1K/2K/4K), and multi-image edit/compose (-i a.png -i b.png). UseGEMINI_API_KEY/GEMINI_IMAGE_MODEL.openai— any OpenAI-compatible image endpoint (OpenAI official, DashScope, new-api gateways, ...). UseOPENAI_API_KEY/OPENAI_BASE_URL/OPENAI_IMAGE_MODEL. Supportsgpt-image-2,dall-e-3, etc.
Prerequisites
uvavailable (the script is a self-containeduv runscript; deps install on first run).The API key for the chosen backend. The script resolves it progressively, so any one works:
export GEMINI_API_KEY=...(gemini backend) orexport OPENAI_API_KEY=...(openai backend), or- a
.envfile (checked in order:$PWD/.env, then${CLAUDE_PLUGIN_ROOT}/.env), or --api-key ...on the command line.
CRITICAL -- Never paste the API key into chat or commit a
.env. If the key is missing, the script prints exactly how to set it — relay that to the user rather than guessing.
Workflow
1. Clarify intent (only if genuinely ambiguous)
A one-line request like "draw a fox in a spacesuit" needs no questions — just generate. Ask (via AskUserQuestion) only when a choice would materially change the result and you cannot reasonably default it, e.g. aspect ratio for a "banner vs. avatar", or whether an attached image should be edited vs. used as style reference.
2. Craft the prompt
Read references/prompting.md before writing a non-trivial prompt. In short: describe
subject, composition, lighting, style, and mood in concrete terms; put any literal text to
render in quotes; and for edits, state what to change AND what to keep. A vivid one-paragraph
prompt beats a terse phrase.
3. Run the script
Invoke it directly (the shebang runs it through uv):
${CLAUDE_PLUGIN_ROOT}/skills/generate-image/scripts/generate_image.py "PROMPT" --backend BACKEND -o OUT.png [flags]
Flags:
| Flag | Purpose | Default |
|---|---|---|
--backend |
gemini (native Google API) or openai (OpenAI-compatible endpoint). No default — also via IMAGE_BACKEND. |
required |
-o, --output |
Output path (.png/.jpeg) |
generated.png |
-i, --input |
Reference/input image (repeatable). gemini: edit/compose multi-image. openai: edit single image (first wins). | none |
--aspect-ratio |
1:1 2:3 3:2 3:4 4:3 4:5 5:4 9:16 16:9 21:9. gemini: via image_config. openai: via extra_body (Gemini-compat endpoints only). |
model decides |
--size |
gemini: 1K/2K/4K. openai: free string (1024x1024, auto, ...). |
model decides |
--count |
Number of images. gemini: N separate calls. openai: one call, n=N. |
1 |
--model |
Model id or alias (else GEMINI_IMAGE_MODEL/OPENAI_IMAGE_MODEL). gemini: pro/flash/raw id. openai: raw id (e.g. gpt-image-2). |
backend default |
--quality |
low/medium/high/auto — openai backend only. |
model decides |
--response-format |
b64_json/url/none — openai backend only. url is downloaded to disk; none omits the param. Some gateways require url or reject the param (use none). |
b64_json |
--base-url |
openai backend only: OpenAI-compatible base URL. Also via IMAGE_BASE_URL/OPENAI_BASE_URL. |
required for openai |
--api-key |
Override the API key (else GEMINI_API_KEY for gemini, OPENAI_API_KEY for openai). |
required |
Models (pass the alias to --model or set the backend's env var):
| Backend | Alias / id | Notes |
|---|---|---|
| gemini | pro (default) → gemini-3-pro-image |
highest quality |
| gemini | flash → gemini-2.5-flash-image |
faster / cheaper |
| openai | gpt-image-2, dall-e-3, gpt-image-1, ... |
any id the endpoint serves |
Examples:
# Gemini, 2K wide banner
generate_image.py "podcast cover art" --backend gemini --aspect-ratio 16:9 --size 2K -o cover.png
# Gemini multi-image compose
generate_image.py "put the watch from image 1 on the wrist in image 2" --backend gemini -i watch.png -i wrist.png -o composite.png
# OpenAI-compatible gateway, gpt-image-2 (this gateway needs url format)
generate_image.py "a red bicycle" --backend openai --base-url https://api.tu-zi.com/v1 \
--model gpt-image-2 --size 1024x1024 --response-format url -o bike.png
# OpenAI official
generate_image.py "a red bicycle" --backend openai --base-url https://api.openai.com/v1 --model gpt-image-2 -o bike.png
When the user wants choices to pick from, request --count 2 (or more) and show all outputs.
With -i, the prompt becomes an edit/compose instruction over the supplied image(s).
4. Report
Tell the user the saved path(s). If nothing was returned, it is usually a safety-filtered prompt — say so and offer a reworded prompt. Output files are images: reference them by path; do not try to inline their bytes.
Configuration is progressive (the key best practice)
Backend, key, base URL, model, and quality are each resolved by
lib/progressive_env.py in this order, stopping at the first hit: CLI flag →
process env → .env chain → built-in default. This is why the same command
works in a project with a local .env, in a shell with exports, or with
everything overridden inline — and why a newer model or a different endpoint can
be selected with export GEMINI_IMAGE_MODEL=... / export OPENAI_BASE_URL=...
without touching code. See references/prompting.md for the parameter reference.
Files
scripts/generate_image.py— the generator (google-genaifor gemini,openaifor openai).references/prompting.md— prompt-writing guide and full parameter reference.${CLAUDE_PLUGIN_ROOT}/lib/progressive_env.py— shared progressive config resolver.