Skills
skills/jezweb/claude-skills/image-gen

image-gen

SKILL.md

Image Generation Skill

Generate and edit website images using Gemini Native Image Generation.

⚠️ Critical: SDK Migration Required

IMPORTANT: The @google/generative-ai package is deprecated as of November 30, 2025. All new projects must use @google/genai.

Migration Required:

// ❌ OLD (deprecated, support ended Nov 30, 2025)
import { GoogleGenerativeAI } from "@google/generative-ai";
const genAI = new GoogleGenerativeAI(API_KEY);

// ✅ NEW (required)
import { GoogleGenAI } from "@google/genai";
const ai = new GoogleGenAI({ apiKey: API_KEY });

Source: GitHub Repository Migration Notice

Models

Model ID Status Best For
Gemini 3 Pro Image gemini-3-pro-image-preview Preview (Nov 20, 2025) 4K, complex prompts, text
Gemini 2.5 Flash Image gemini-2.5-flash-image GA (Oct 2, 2025) Fast iteration, general use
Imagen 4.0 imagen-4.0-generate-001 GA (Aug 14, 2025) Alternative platform

Deprecated Models (do not use):

  • gemini-2.0-flash-exp-image-generation - Shut down Nov 11, 2025
  • gemini-2.0-flash-preview-image-generation - Shut down Nov 11, 2025
  • gemini-2.5-flash-image-preview - Scheduled shutdown Jan 15, 2026

Source: Google AI Changelog

Capabilities

Feature Supported
Generate from text ✅
Edit existing images ✅
Change aspect ratio ✅
Widen/extend images ✅
Style transfer ✅
Change colours ✅
Add/remove elements ✅
Text in images ✅ (legible!)
Multiple reference images ✅ (up to 14: max 5 humans, 9 objects)
4K resolution ✅ (Pro only)

Note: Exceeding 5 human reference images causes unpredictable character consistency. Keep human images ≤ 5 for reliable results.

Aspect Ratios

1:1   | 2:3  | 3:2  | 3:4  | 4:3
4:5   | 5:4  | 9:16 | 16:9 | 21:9

Resolutions (Pro only)

Size 1:1 16:9 4:3
1K 1024x1024 1376x768 1184x880
2K 2048x2048 2752x1536 2368x1760
4K 4096x4096 5504x3072 4736x3520

Quick Start

import { GoogleGenAI } from "@google/genai";

const ai = new GoogleGenAI({ apiKey: process.env.GEMINI_API_KEY });

// Generate new image
const response = await ai.models.generateContent({
  model: "gemini-2.5-flash-image",
  contents: "A professional plumber in hi-vis working in modern Australian home",
  config: {
    responseModalities: ["TEXT", "IMAGE"],  // BOTH required - cannot use ["IMAGE"] alone
    imageGenerationConfig: {
      aspectRatio: "16:9",
    },
  },
});

// Extract image
for (const part of response.candidates[0].content.parts) {
  if (part.inlineData) {
    const buffer = Buffer.from(part.inlineData.data, "base64");
    fs.writeFileSync("hero.png", buffer);
  }
}

Important: responseModalities must include both ["TEXT", "IMAGE"]. Using ["IMAGE"] alone may fail or produce unexpected results.

Model Selection

Requirement Use
Fast iteration Gemini 2.5 Flash Image
4K resolution Gemini 3 Pro Image Preview
Text in images Gemini 3 Pro (94% legibility at 4K)
Simple edits Gemini 2.5 Flash Image
Complex compositions Gemini 3 Pro Image Preview
Infographics/diagrams Gemini 3 Pro Image Preview

Text Rendering Benchmarks (4K resolution):

  • Gemini 3 Pro Image: 94% legible text
  • DALL-E 3: 78% legible text
  • Midjourney: Decorative pseudo-text only

When to Use

Use Gemini Image Gen when:

  • Stock photos don't fit brand/context
  • Need Australian-specific imagery
  • Need text in images (infographics, diagrams)
  • Need consistent style across multiple images
  • Need to edit/modify existing images
  • Client has no photos of their work

Don't use when:

  • Client has good photos of actual work
  • Real team photos needed (discuss first)
  • Product shots (use real products)
  • Legal/compliance concerns

Known Issues Prevention

This skill prevents 5 documented issues:

Issue #1: Resolution Parameter Case Sensitivity

Error: Request fails with invalid parameter error Source: Google AI Image Generation Docs Why It Happens: Resolution values are case-sensitive and must use uppercase 'K'. Prevention: Always use "4K", "2K", "1K" - never lowercase "4k".

// ❌ WRONG - causes request failure
config: { imageGenerationConfig: { resolution: "4k" } }

// ✅ CORRECT - uppercase required
config: { imageGenerationConfig: { resolution: "4K" } }

Issue #2: Aspect Ratio May Be Ignored (Sept 2025+)

Error: Returns 1:1 square image despite requesting 16:9 or other ratios Source: Google Support Thread Why It Happens: Backend update in September 2025 affected Gemini 2.5 Flash Image model's aspect ratio handling. Prevention: Use Gemini 3 Pro Image Preview for reliable aspect ratio control, or generate 1:1 and use multi-turn editing to extend.

// May ignore aspectRatio on Gemini 2.5 Flash Image
model: "gemini-2.5-flash-image",
config: { imageGenerationConfig: { aspectRatio: "16:9" } }

// More reliable for aspect ratio control
model: "gemini-3-pro-image-preview",
config: { imageGenerationConfig: { aspectRatio: "16:9" } }

Status: Google confirmed working on fix (Sept 2025).

Issue #3: Exceeding 5 Human Reference Images

Error: Unpredictable character consistency in generated images Source: Google AI Image Generation Docs Why It Happens: Gemini 3 Pro Image supports up to 14 reference images total, but only 5 can be human images for character consistency. Prevention: Limit human images to 5 or fewer. Use remaining slots (up to 14 total) for objects/scenes.

// ❌ WRONG - 7 human images exceeds limit
const humanImages = [img1, img2, img3, img4, img5, img6, img7];
const prompt = [
  { text: "Generate consistent characters" },
  ...humanImages.map(img => ({ inlineData: { data: img, mimeType: "image/png" }})),
];

// ✅ CORRECT - max 5 human images
const humanImages = images.slice(0, 5);  // Limit to 5
const objectImages = images.slice(5, 14);  // Up to 9 more for objects
const prompt = [
  { text: "Generate consistent characters" },
  ...humanImages.map(img => ({ inlineData: { data: img, mimeType: "image/png" }})),
  ...objectImages.map(img => ({ inlineData: { data: img, mimeType: "image/png" }})),
];

Issue #4: SynthID Watermark Cannot Be Disabled

Error: N/A (documented limitation) Source: Google AI Image Generation Docs Why It Happens: All generated images automatically include a SynthID watermark for content authenticity tracking. Prevention: Be aware of this limitation for commercial use cases. Watermark cannot be disabled by developers.

Issue #5: Google Search Grounding Excludes Image Results

Error: Generated images don't reflect visual search results, only text Source: Google AI Image Generation Docs Why It Happens: When using Google Search tool with image generation, "image-based search results are not passed to the generation model." Prevention: Only text-based search results inform the visual output. Don't expect the model to reference images from search results.

// Google Search tool enabled
const response = await ai.models.generateContent({
  model: "gemini-3-pro-image-preview",
  contents: "Generate image of latest iPhone design",
  tools: [{ googleSearch: {} }],
  config: { responseModalities: ["TEXT", "IMAGE"] },
});
// Result: Only text search results used, not image results from web search

Pricing

Current Pricing (as of November 2025):

  • Gemini 2.5 Flash Image: ~$0.008 per image
    • Input: 258 tokens per image
    • Output: 1290 tokens per image
    • Rate: $30.00 per 1M output tokens

Note: The generateImages API (Imagen models) does not return usageMetadata in responses. Track costs manually based on pricing above.

Source: Google Developers Blog - Gemini 2.5 Flash Image

Reference Files

  • references/prompting.md - Effective prompt patterns
  • references/website-images.md - Hero, service, background templates
  • references/editing.md - Multi-turn editing patterns
  • references/local-imagery.md - Australian-specific details
  • references/integration.md - API code examples

Last verified: 2026-01-21 | Skill version: 2.0.0 | Changes: Added SDK migration notice (critical), updated to current model names (gemini-3-pro-image-preview, gemini-2.5-flash-image), added 5 Known Issues (resolution case sensitivity, aspect ratio bug, reference image limits, SynthID watermark, Google Search grounding), added pricing section, added text rendering benchmarks.

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Repository
jezweb/claude-skills
Installed on
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