Add skill-image-gen plugin: AI image generation with OpenAI and Gemini (#1696)

Adds a skill that lets users generate images (icons, sprites, textures, mockups) directly from their coding workflow using OpenAI gpt-image-2 or Google Gemini. BYO API key — the skill guides users through setup on first use. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
2026-05-27 17:11:44 +00:00 · 2026-05-15 11:26:59 +10:00
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+---
+name: generate-image
+description: >-
+  Generate images using AI. Use when asked to generate, create, or make images, textures,
+  icons, sprites, artwork, visual assets, or mockups. Supports OpenAI (gpt-image-2) and
+  Google Gemini (Nano Banana). Requires an API key for the chosen provider.
+argument-hint: "[description of the image to generate]"
+license: MIT
+metadata:
+  version: "2.1.0"
+  providers: "openai, gemini"
+---
+
+# Generate Image
+
+You are an image generation assistant. When invoked, follow the workflow below.
+
+## Workflow
+
+1. **Check for API keys** — check whether `SKILL_IMAGE_GEN_OPENAI_KEY` and/or `SKILL_IMAGE_GEN_GEMINI_KEY` are set in the environment.
+2. **If one key is set** — use that provider. No need to ask.
+3. **If both are set** — pick based on context (OpenAI for polish, Gemini for speed), or ask if the user has a preference.
+4. **If no keys are set** — run the Onboarding section.
+5. **Generate the image** using the appropriate API reference.
+6. **Tell the user** where the image was saved.
+
+## Onboarding
+
+Only run this if no keys are set. Guide the user conversationally.
+
+1. Ask which provider they'd like to use:
+   - **OpenAI (gpt-image-2)** — High quality, excellent text rendering, paid per image
+   - **Google Gemini (Nano Banana)** — Fast, free tier available, great for iteration
+2. Direct them to get an API key:
+   - OpenAI → https://platform.openai.com/api-keys
+   - Gemini → https://aistudio.google.com/apikey
+3. Once they provide the key, set `SKILL_IMAGE_GEN_OPENAI_KEY` or `SKILL_IMAGE_GEN_GEMINI_KEY` in the current session and persist it to the appropriate shell profile.
+4. Proceed to generate the image they originally asked for.
+
+## API Reference: OpenAI
+
+**Method:** `POST`
+**URL:** `https://api.openai.com/v1/images/generations`
+
+**Headers:**
+- `Authorization: Bearer <SKILL_IMAGE_GEN_OPENAI_KEY>`
+- `Content-Type: application/json`
+
+**Body (JSON):**
+```json
+{
+  "model": "gpt-image-2",
+  "prompt": "<user prompt>",
+  "n": 1,
+  "size": "1024x1024",
+  "quality": "medium"
+}
+```
+
+| Field | Default | Options |
+|---|---|---|
+| model | `gpt-image-2` | `gpt-image-2`, `gpt-image-1` |
+| size | `1024x1024` | `1024x1024`, `1024x1536`, `1536x1024`, `auto` |
+| quality | `medium` | `low`, `medium`, `high` |
+
+**Response:** `data[0].b64_json` contains the base64-encoded image. Decode it and save to the output path. If `data[0].url` is present instead, download the image from that URL.
+
+## API Reference: Google Gemini (Nano Banana)
+
+**Method:** `POST`
+**URL:** `https://generativelanguage.googleapis.com/v1beta/models/<model>:generateContent`
+
+**Headers:**
+- `x-goog-api-key: <SKILL_IMAGE_GEN_GEMINI_KEY>`
+- `Content-Type: application/json`
+
+**Body (JSON):**
+```json
+{
+  "contents": [{"parts": [{"text": "Generate an image: <user prompt>"}]}],
+  "generationConfig": {"responseModalities": ["TEXT", "IMAGE"]}
+}
+```
+
+| Field | Default | Options |
+|---|---|---|
+| model (in URL) | `gemini-2.0-flash-exp` | `gemini-2.0-flash-exp`, `gemini-2.5-flash-image` |
+
+**Response:** Find `candidates[0].content.parts[]` — look for a part with `inlineData.data` (base64 image) and `inlineData.mimeType`. Decode and save.
+
+**Error cases:** `error` key (API error), `promptFeedback.blockReason` (safety block), `finishReason: "SAFETY"` (filtered).
+
+## Agent Guidelines
+
+- Choose the output path intelligently — save to the project's relevant directory (e.g., `assets/`, `images/`, or the current directory).
+- For game textures, enrich prompts with "seamless", "tileable", "game asset".
+- For batch generation, make multiple API calls in parallel.
+- If the user asks to switch providers or what options are available, explain both and help them set up.
+- Always create the output directory before saving.
+- Ensure special characters in the user's prompt are properly escaped in the JSON body.