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Gemini Image Generation Models

Package alias notes. Verify current Google model IDs before use. Do not treat these as Google-confirmed current model IDs.

Package Model Aliases

gemini-3.1-flash-image-preview (Unverified package-specific alias)

Property Value
Model ID gemini-3.1-flash-image-preview (verify in installed MCP/tool config)
Tier Package label: Nano Banana 2 (Flash)
Speed Fast - optimized for high-volume use
Aspect Ratios All 14 ratios (see table below)
Max Resolution Up to 4096×4096 (4K tier)
Features Google Search grounding (web + image), thinking levels, image-only output, extreme aspect ratios
Rate Limits (Free) ~10 RPM / ~500 RPD (per Google Cloud project, resets midnight Pacific)
Output Tokens ~1,290 output tokens per image
Best For Most use cases, rapid iteration, batch generation

gemini-2.5-flash-image

Property Value
Model ID gemini-2.5-flash-image
Tier Nano Banana 2 (Flash, previous gen)
Speed Fast
Aspect Ratios 1:1, 16:9, 9:16, 4:3, 3:4
Max Resolution Up to 1024×1024 (1K tier)
Rate Limits (Free) ~10 RPM / ~500 RPD
Best For Stable fallback, proven quality

Deprecated Models (DO NOT USE)

gemini-3-pro-image-preview

gemini-2.0-flash-exp

Aspect Ratios

All 14 supported ratios. Availability varies by model:

Ratio Orientation Use Cases 3.1 Flash 2.5 Flash
1:1 Square Social posts, avatars, thumbnails ✅ ✅
16:9 Landscape Blog headers, YouTube thumbnails, presentations ✅ ✅
9:16 Portrait Stories, Reels, TikTok, mobile ✅ ✅
4:3 Landscape Product shots, classic display ✅ ✅
3:4 Portrait Book covers, portrait framing ✅ ✅
2:3 Portrait Pinterest pins, posters ✅ ❌
3:2 Landscape DSLR standard, photo prints ✅ ❌
4:5 Portrait Instagram portrait, social ✅ ❌
5:4 Landscape Large format photography ✅ ❌
1:4 Tall strip Vertical banners, side panels ✅ ❌
4:1 Wide strip Website banners, headers ✅ ❌
1:8 Extreme tall Narrow vertical strips ✅ ❌
8:1 Extreme wide Ultra-wide banners ✅ ❌
21:9 Ultra-wide Cinematic, film-grade, ultra-wide monitors ✅ ❌

Resolution Tiers

Control output resolution with the imageSize parameter. Note the uppercase K requirement.

imageSize Value Pixel Range Model Availability Use Case
512 Up to 512×512 All models Drafts, quick iteration, low bandwidth
1K (default) Up to 1024×1024 All models Standard web use, social media
2K Up to 2048×2048 3.1 Flash Quality assets, detailed work
4K Up to 4096×4096 3.1 Flash Print production, hero images, final assets

Notes: - Actual pixel dimensions depend on aspect ratio (e.g., 4K at 16:9 = 4096×2304) - Higher resolutions consume more tokens and cost more - Default is 1K if imageSize is not specified

API Configuration

Endpoint

https://generativelanguage.googleapis.com/v1beta/models/{model-id}:generateContent

Required Parameters

{
  "contents": [{"parts": [{"text": "your prompt here"}]}],
  "generationConfig": {
    "responseModalities": ["TEXT", "IMAGE"],
    "imageConfig": {
      "aspectRatio": "16:9",
      "imageSize": "1K"
    }
  }
}

Image-Only Output Mode

Force the model to return only an image (no text response):

{
  "generationConfig": {
    "responseModalities": ["IMAGE"]
  }
}

Thinking Level

Control how much the model "thinks" before generating. Higher levels improve complex compositions but increase latency:

{
  "generationConfig": {
    "thinkingConfig": {
      "thinkingLevel": "medium"
    }
  }
}

Levels: minimal, low, medium, high

Google Search Grounding

Ground generation in real-world visual references. Supports web and image search (3.1 Flash):

{
  "tools": [{"googleSearch": {}}]
}

Prompt pattern: [Search/source request] + [Analytical task] + [Visual translation]

Example: "Search for the latest SpaceX Starship design, analyze its proportions and markings, then generate a photorealistic image of it at sunset on the launch pad."

Multi-Image Input

Up to 14 reference images can be provided: - 10 object references: for style, composition, or visual matching - 4 character references: assign distinct names to preserve features across generations

Useful for character consistency, style transfer, and brand-aligned generation.

Rate Limits by Tier

Tier RPM RPD Notes
Free ~10 ~500 Per Google Cloud project, resets midnight Pacific. Reduced Dec 2025.
Pay-as-you-go 30 10,000 Production workloads
Enterprise Custom Custom Contact Google

Pricing

Model Resolution Cost per Image Notes
3.1 Flash 1K ~$0.039 Standard
3.1 Flash 2K ~$0.078 2× standard
3.1 Flash 4K ~$0.156 4× standard
2.5 Flash 1K ~$0.039 Standard
Batch API Any 50% discount Asynchronous, higher latency

Pricing is approximate and based on ~1,290 output tokens per image. Research suggests NB2 pricing may be ~$0.067/img (vs documented $0.039). Verify current pricing at https://ai.google.dev/gemini-api/docs/pricing

Image Output Specs

Property Value
Format PNG
Max Resolution Up to 4096×4096 (4K tier, 3.1 Flash)
Color Space sRGB
Text Rendering Supported - best under 25 characters
Style Control Via prompt engineering

Safety Filters

Gemini uses a two-layer safety architecture:

  1. Input filters: block prompts containing prohibited content before generation
  2. Output filters: analyze generated images and block unsafe results
finishReason Meaning Retryable?
STOP Successful generation N/A
IMAGE_SAFETY Output blocked by safety filter Rephrase prompt
PROHIBITED_CONTENT Content policy violation No - topic is blocked
SAFETY General safety block Rephrase prompt
RECITATION Detected copyrighted content Rephrase prompt

Known issue: Filters are known to be overly cautious. Benign prompts may be blocked. Iterate with rephrased wording if this happens.

Content Credentials

Key Limitations