Gemini image generation

The gemini engine exposes Gemini 2.5 Flash Image — the same underlying model product as Google's nano-banana-* variants, but via the direct Gemini API rather than Vertex AI. Simpler input shape: no aspect-ratio or resolution picker, just prompt (+ optional reference images for edits) and a quantity. Uses operation as the discriminator, mirroring most other imageGen engines.

Gemini vs Google

If you want explicit aspect-ratio control, resolution tiers, or web-search grounding, use the google engine with model: "nano-banana-2" — same product, richer controls. Pick gemini when you want the minimal shape and the direct Gemini-API semantics.

Prerequisites

• For editImage: 1–4 source images (URLs, data URLs, or Base64)

Text-to-image (createImage)

POST https://orchestration.civitai.com/v2/consumer/workflows?wait=60
Authorization: Bearer <your-token>
Content-Type: application/json

{
  "steps": [{
    "$type": "imageGen",
    "input": {
      "engine": "gemini",
      "model": "2.5-flash",
      "operation": "createImage",
      "prompt": "A photorealistic portrait of a woman with flowers in her hair, golden hour lighting",
      "quantity": 1
    }
  }]
}

POST/v2/consumer/workflows

Set your Civitai API token via the Token button in the navbar to enable Try It.

Request body — edit to customize (e.g. swap the image URL or prompt)

{ "steps": [ { "$type": "imageGen", "input": { "engine": "gemini", "model": "2.5-flash", "operation": "createImage", "prompt": "A photorealistic portrait of a woman with flowers in her hair, golden hour lighting", "quantity": 1 } } ] }

Valid JSON

Image editing (editImage)

{
  "steps": [{
    "$type": "imageGen",
    "input": {
      "engine": "gemini",
      "model": "2.5-flash",
      "operation": "editImage",
      "prompt": "Make it a winter scene with snow falling",
      "images": [
        "https://image.civitai.com/.../source.jpeg"
      ]
    }
  }]
}

POST/v2/consumer/workflows

Set your Civitai API token via the Token button in the navbar to enable Try It.

Request body — edit to customize (e.g. swap the image URL or prompt)

{ "steps": [ { "$type": "imageGen", "input": { "engine": "gemini", "model": "2.5-flash", "operation": "editImage", "prompt": "Make it a winter scene with snow falling", "images": [ "https://image.civitai.com/xG1nkqKTMzGDvpLrqFT7WA/dd4b4ad5-040f-4f0e-baa3-6e1ff00add65/original=true,quality=90,optimized=true/26781018.jpeg" ] } } ] }

Valid JSON

Pass 1–4 reference images in images[] — the prompt is treated as an edit instruction applied across them.

Parameters

Field	Required	Default	Notes
model	✅	—	Only 2.5-flash exposed today.
operation	✅	—	createImage or editImage.
prompt	✅	—	Natural-language. No explicit cap documented; keep it reasonable.
quantity		1	1–4.
images[]	✅ on editImage	—	1–4 entries. URLs, data URLs, or Base64.

No aspect-ratio control, no resolution tier, no seed, no safety toggle. If you need any of those, switch to the google engine with nano-banana-2.

Reading the result

Standard imageGen output: an images[] array, one entry per quantity (shape and URL expiry).

Runtime

Typical wall time 8–20 s per image including queue. wait=60 is comfortable for quantity: 1–2; larger batches or busy periods warrant wait=0 + polling.

Cost

Preview the exact charge with whatif=true (Payments (Buzz)).

Flat per-image:

total = 60 × quantity

Shape	Buzz
createImage, quantity: 1	~60
editImage with 1 reference	~60
createImage, quantity: 4	~240

Gemini 2.5 Flash's price doesn't depend on resolution (there's no resolution field) or the number of reference images. If you need the same product with tiered resolution pricing, the google engine's nano-banana-2 costs more at 1K (~104 Buzz) but adds a tiered scale for 2K / 4K.

Troubleshooting

Timeouts, moderation blocks and expired blob URLs: see Common troubleshooting. blocked comes from Google's content filter.

Symptom	Likely cause	Fix
400 with unknown property aspectRatio / resolution	Those fields live on the google engine, not gemini	Switch engines, or drop the field.
400 with "images minItems" on editImage	Empty images[]	Include at least one source image when operation: "editImage".
400 with "images maxItems"	More than 4 source images	Trim to 4 — google/nano-banana-2 accepts up to 10 if you need more.
Output doesn't look edited	Prompt described target state rather than the change	Phrase as an instruction ("Make it a winter scene") rather than a description of the result.

Related

• SubmitWorkflow · GetWorkflow
• Google image generation — Nano Banana / Imagen 4 via Vertex AI (alternate routing with richer controls)
• OpenAI image generation — alternative commercial tier
• Flux 2 / Flux 1 / Qwen — open-weights alternatives on Civitai-hosted workers
• Full parameter catalog: the Gemini25FlashCreateImageGenInput and Gemini25FlashEditImageGenInput schemas in the API reference
• imageGen OpenAPI spec