Image Gen

Model Capability Matrix

When to Use Nano Banana (Critical)

Use Nano Banana whenever the user's request involves:

• Storyboard / 分镜图: Multiple frames that tell a story with the same characters
• Comic strip / 漫画: Sequential panels with consistent characters
• Character series: Multiple images of the same person/character in different poses or scenes
• Scene continuation: "Now show the same girl in the forest" (referencing a previous image)
• Style consistency: A set of images that must share the same visual style/world

Nano Banana uses Google's Gemini 3 Pro multimodal architecture, which understands context holistically rather than keyword-matching. It supports up to 14 reference images for maintaining character and scene consistency.

How to Use This Skill

1. Analyze the request: Is it a single image or a series? Does it need context continuity?
2. Select model: Use the decision tree above.
3. Enhance the prompt: Add style, lighting, and quality descriptors appropriate for the model.
4. Inform the user: Tell them which model you're using and why, and that generation has started.
5. Run the script: Use exec tool with sufficient timeout.
6. Deliver the result: Send image URL(s) to the user.

Calling the Generation Script

node {baseDir}/generate.js \
  --model <model_id> \
  --prompt "<enhanced prompt>" \
  [--aspect-ratio <ratio>] \
  [--num-images <1-4>] \
  [--negative-prompt "<negative prompt>"] \
  [--reference-images "<url1,url2,...>"]

Parameters:

• --model: One of midjourney, flux-pro, flux-dev, flux-schnell, sdxl, nano-banana, ideogram, recraft
• --prompt: The image generation prompt (required)
• --aspect-ratio: e.g. 16:9, 1:1, 9:16, 4:3, 3:4 (default: 1:1)
• --num-images: 1-4 (default: 1; Midjourney always returns 4 regardless)
• --negative-prompt: Things to avoid (not supported by Midjourney)
• --reference-images: Comma-separated image URLs for context/character consistency (Nano Banana only)
• --mode: Midjourney speed: turbo (default, ~20-40s), fast (~30-60s), relax (free but slow)

exec timeout: Set at least 120 seconds for Midjourney and Nano Banana; 30 seconds is sufficient for Flux Schnell.

⚡ Midjourney Workflow (Sync Mode — No --async)

Always use sync mode (no --async). The script waits internally until complete.

node {baseDir}/generate.js \
  --model midjourney \
  --prompt "<enhanced prompt>" \
  --aspect-ratio 16:9

Understanding Midjourney Output

{
  "success": true,
  "model": "midjourney",
  "jobId": "xxxxxxxx-...",
  "imageUrl": "https://cdn.legnext.ai/temp/....png",
  "imageUrls": [
    "https://cdn.legnext.ai/mj/xxxx_0.png",
    "https://cdn.legnext.ai/mj/xxxx_1.png",
    "https://cdn.legnext.ai/mj/xxxx_2.png",
    "https://cdn.legnext.ai/mj/xxxx_3.png"
  ]
}

CRITICAL — image field meanings:

"放大第N张" / "要第N张" / "give me image N" = send imageUrls[N-1] directly. Do NOT call generate.js again.

Midjourney Interaction Flow

After generation:

🎨 生成完成！这是 4 张图的预览： 预览图 你喜欢哪一张？回复 1、2、3 或 4，我直接发给你高清单图。

When user picks image N:

这是第 N 张的单独高清图： 图片 N

🤖 Nano Banana (Gemini) Workflow

Use for storyboards, character series, and any context-dependent multi-image generation.

Single image (no reference)

node {baseDir}/generate.js \
  --model nano-banana \
  --prompt "<detailed scene description>" \
  --aspect-ratio 16:9

With reference images (character/scene consistency)

node {baseDir}/generate.js \
  --model nano-banana \
  --prompt "<scene description, referencing the character/style from the reference images>" \
  --aspect-ratio 16:9 \
  --reference-images "https://url-of-previous-image-1.png,https://url-of-previous-image-2.png"

How to build a storyboard series:

1. Generate the first frame without reference images (establishes the character/scene)
2. Use the first frame's URL as --reference-images for the second frame
3. For subsequent frames, use the most recent 1-3 images as references to maintain consistency
4. Keep the character description consistent across all prompts

Example storyboard workflow:

Frame 1: node generate.js --model nano-banana --prompt "A young girl with red hair, wearing a blue dress, sitting under a magical treehouse in an enchanted forest, warm golden light, storybook illustration style" --aspect-ratio 16:9

Frame 2: node generate.js --model nano-banana --prompt "The same red-haired girl in blue dress climbing the rope ladder up to the treehouse, excited expression, enchanted forest background, same storybook illustration style" --aspect-ratio 16:9 --reference-images "<frame1_url>"

Frame 3: node generate.js --model nano-banana --prompt "Inside the magical treehouse, the red-haired girl discovers a glowing book on a wooden shelf, wonder on her face, warm candlelight, same storybook illustration style" --aspect-ratio 16:9 --reference-images "<frame1_url>,<frame2_url>"

Nano Banana Output

{
  "success": true,
  "model": "nano-banana",
  "images": ["https://v3b.fal.media/files/...png"],
  "imageUrl": "https://v3b.fal.media/files/...png"
}

Send imageUrl directly to the user (no grid, single image).

Other Models

Flux Pro / Dev / Schnell

Best for photorealistic standalone images. Output format same as Nano Banana (single imageUrl).

node {baseDir}/generate.js --model flux-pro --prompt "<prompt>" --aspect-ratio 16:9

Ideogram v3

Best for images containing text (logos, posters, signs).

node {baseDir}/generate.js --model ideogram --prompt "A motivational poster with text 'DREAM BIG' in bold typography, sunset gradient background" --aspect-ratio 3:4

Recraft v3

Best for vector-style, icons, flat design.

node {baseDir}/generate.js --model recraft --prompt "A minimal flat design app icon, blue gradient, abstract geometric shape" --aspect-ratio 1:1

Prompt Enhancement Tips

For Midjourney: Add cinematic lighting, ultra detailed, --v 7, --style raw. Legnext supports all MJ parameters.

For Nano Banana: Use natural language descriptions. Describe the character consistently across frames (hair color, clothing, expression). Mention "same style as reference" or "consistent with previous frame".

For Flux: Add masterpiece, highly detailed, sharp focus, professional photography, 8k.

For Ideogram: Be explicit about text content, font style, layout, and color scheme.

For Recraft: Specify vector illustration, flat design, icon style, minimal.

Example Conversations

User: "帮我画一只赛博朋克猫" → Single artistic image → Midjourney → Tell user "🎨 正在用 Midjourney 生成，约 30 秒..." → Send grid preview, ask which one they want

User: "帮我生成一套分镜图，讲述一个女孩在魔法森林的冒险" → Multiple frames with story continuity → Nano Banana → Tell user "🎨 这类有上下文关联的分镜图用 Gemini 生成，能保持角色一致性..." → Generate frame by frame, using previous frames as reference images

User: "要第2张" / "放大第2张" (after Midjourney generation) → Send imageUrls[1] directly. No need to call generate.js again.

User: "做一个 App 图标，蓝色系扁平风格" → Vector/icon → Recraft

User: "生成一张带有'欢迎光临'文字的门牌图" → Text in image → Ideogram

User: "快速生成个草稿看看效果" → Speed priority → Flux Schnell (<2s)

User: "生成一张产品海报，白色背景，一瓶香水" → Photorealistic product → Flux Pro

Environment Variables