Image Generation MCP

/** * Gemini/Nano Banana image generation provider. * Supports both gemini-2.5-flash-image and gemini-3-pro-image-preview models. */ import { GoogleGenAI } from "@google/genai"; import { toGeminiAspectRatio } from "../config/presets.js"; import { GeneratedImage, ImageGenerationOptions, ImageProvider, ProviderConfig, ProviderError, } from "./types.js"; type GeminiModel = "gemini-2.5-flash-image" | "gemini-3-pro-image-preview"; type GeminiAspectRatio = "1:1" | "16:9" | "9:16" | "4:3" | "3:4"; interface GeminiProviderConfig extends ProviderConfig { /** Default model to use */ defaultModel?: GeminiModel; } export class GeminiProvider implements ImageProvider { readonly name = "gemini"; private client: GoogleGenAI | null = null; private config: GeminiProviderConfig; // Gemini-supported aspect ratios private static readonly SUPPORTED_ASPECT_RATIOS: GeminiAspectRatio[] = [ "1:1", "16:9", "9:16", "4:3", "3:4", ]; constructor(config: GeminiProviderConfig = {}) { this.config = { timeout: 60000, maxRetries: 2, defaultModel: "gemini-2.5-flash-image", ...config, }; // Initialize client if API key is available const apiKey = config.apiKey || process.env.GOOGLE_API_KEY; if (apiKey) { this.client = new GoogleGenAI({ apiKey }); } } isConfigured(): boolean { return this.client !== null; } getSupportedAspectRatios(): string[] { return [...GeminiProvider.SUPPORTED_ASPECT_RATIOS]; } getMaxResolution(): { width: number; height: number } { // Gemini 3 Pro supports up to 4K return { width: 4096, height: 4096 }; } async generateImage(options: ImageGenerationOptions): Promise<GeneratedImage> { if (!this.client) { throw new ProviderError( "Gemini provider not configured. Set GOOGLE_API_KEY environment variable.", this.name, "NOT_CONFIGURED" ); } // Select model based on quality requirement const model: GeminiModel = options.quality === "high" ? "gemini-3-pro-image-preview" : (this.config.defaultModel ?? "gemini-2.5-flash-image"); // Map aspect ratio to Gemini-compatible format const aspectRatio = toGeminiAspectRatio(options.aspectRatio); // Build the prompt with optional style let fullPrompt = options.prompt; if (options.style) { fullPrompt = `${options.style} style: ${options.prompt}`; } try { const response = await this.client.models.generateContent({ model, contents: [{ role: "user", parts: [{ text: fullPrompt }] }], config: { responseModalities: ["TEXT", "IMAGE"], imageConfig: { aspectRatio, // For Pro model, we can request higher resolution ...(model === "gemini-3-pro-image-preview" && options.width > 1500 ? { imageSize: options.width > 3000 ? "4K" : "2K" } : {}), }, }, }); // Extract image from response const candidate = response.candidates?.[0]; if (!candidate?.content?.parts) { throw new ProviderError("No image generated in response", this.name, "NO_IMAGE", true); } // Find the image part in the response for (const part of candidate.content.parts) { if (part.inlineData?.mimeType?.startsWith("image/")) { const imageData = part.inlineData.data; // Validate that we actually have image data if (!imageData || imageData.length === 0) { throw new ProviderError( "Empty image data in response", this.name, "EMPTY_IMAGE_DATA", true ); } // Calculate actual dimensions based on Gemini's aspect ratio behavior // Gemini returns images at these standard sizes for each aspect ratio const actualDimensions = this.getActualDimensions( aspectRatio, options.width, options.height ); return { base64Data: imageData, mimeType: part.inlineData.mimeType, width: actualDimensions.width, height: actualDimensions.height, metadata: { model, aspectRatio, requestedWidth: options.width, requestedHeight: options.height, promptTokens: response.usageMetadata?.promptTokenCount, candidatesTokens: response.usageMetadata?.candidatesTokenCount, }, }; } } throw new ProviderError("No image data found in response", this.name, "NO_IMAGE_DATA", true); } catch (error) { // Re-throw ProviderErrors as-is if (error instanceof ProviderError) { throw error; } // Wrap other errors const message = error instanceof Error ? error.message : "Unknown error"; const isRetryable = message.includes("rate limit") || message.includes("timeout") || message.includes("503"); throw new ProviderError(`Gemini API error: ${message}`, this.name, "API_ERROR", isRetryable); } } /** * Get actual dimensions that Gemini will produce for a given aspect ratio. * Gemini generates images at standard sizes based on the aspect ratio. */ private getActualDimensions( aspectRatio: GeminiAspectRatio, requestedWidth: number, _requestedHeight: number ): { width: number; height: number } { // Gemini's standard output sizes (approximate - may vary by model) // These are based on observed outputs and API documentation const standardSizes: Record<GeminiAspectRatio, { width: number; height: number }> = { "1:1": { width: 1024, height: 1024 }, "16:9": { width: 1536, height: 864 }, "9:16": { width: 864, height: 1536 }, "4:3": { width: 1280, height: 960 }, "3:4": { width: 960, height: 1280 }, }; // For high-resolution requests on Pro model, dimensions may be larger if (requestedWidth > 1500) { // Scale up proportionally for larger requests const base = standardSizes[aspectRatio]; const scale = requestedWidth > 3000 ? 2.5 : 1.5; return { width: Math.round(base.width * scale), height: Math.round(base.height * scale), }; } return standardSizes[aspectRatio]; } }