feat: add image generation for OpenAI DALL-E and Gemini Imagen

New `/v1/images/generations` endpoint proxies DALL-E 2/3 (OpenAI)
and Imagen 3 (Gemini). Same auth/logging as chat completions.

- Add ImageGenerationRequest/Response models
- Extend Provider interface with ImageGeneration()
- OpenAI: forward to /v1/images/generations
- Gemini: call /v1beta/models/{model}:predict, map OpenAI params
- Circuit breaker wraps image gen like chat completions
- Model routing: dall-e* -> openai, imagen*/gemini* -> gemini
- Unsupported providers (deepseek/moonshot/grok/ollama) return error
- Fix pre-existing CachedContentTokenCount bug in StreamGemini

README.md

@@ -4,10 +4,10 @@ A unified, high-performance LLM proxy gateway built in Go. It provides a single
 
 ## Features
 
-- **Unified API:** OpenAI-compatible `/v1/chat/completions` and `/v1/models` endpoints.
+- **Unified API:** OpenAI-compatible `/v1/chat/completions`, `/v1/images/generations`, and `/v1/models` endpoints.
 - **Multi-Provider Support:**
-  - **OpenAI:** GPT-4o, GPT-4o Mini, o1, o3 reasoning models.
-  - **Google Gemini:** Gemini 2.0 Flash, Pro, and vision models (with native CoT support).
+  - **OpenAI:** GPT-4o, GPT-4o Mini, o1, o3 reasoning models, DALL-E 2/3 image generation.
+  - **Google Gemini:** Gemini 2.0 Flash, Pro, and vision models (with native CoT support), Imagen 3 image generation.
   - **DeepSeek:** DeepSeek Chat and Reasoner (R1) models.
   - **Moonshot:** Kimi K2.5 and other Kimi models.
   - **xAI Grok:** Grok-4 models.
@@ -18,6 +18,7 @@ A unified, high-performance LLM proxy gateway built in Go. It provides a single
   - **Database Persistence:** Every request logged to SQLite for historical analysis and dashboard analytics.
   - **Streaming Support:** Full SSE (Server-Sent Events) support for all providers.
 - **Multimodal (Vision):** Image processing (Base64 and remote URLs) across compatible providers.
+- **Image Generation:** DALL-E 2/3 (OpenAI) and Imagen 3 (Gemini) via OpenAI-compatible `/v1/images/generations` endpoint.
 - **Multi-User Access Control:**
   - **Admin Role:** Full access to all dashboard features, user management, and system configuration.
   - **Viewer Role:** Read-only access to usage analytics, costs, and monitoring.
@@ -54,6 +55,7 @@ GopherGate is designed with security in mind:
 ### Quick Start
 
 1. Clone and build:
+
    ```bash
    git clone <repository-url>
    cd gophergate
@@ -61,6 +63,7 @@ GopherGate is designed with security in mind:
    ```
 
 2. Configure environment:
+
    ```bash
    cp .env.example .env
    # Edit .env and add your configuration:
@@ -112,6 +115,7 @@ Access the dashboard at `http://localhost:8080`.
 
 **Forgot Password?**
 You can reset the admin password to default by running:
+
 ```bash
 ./gophergate -reset-admin
 ```
@@ -129,6 +133,7 @@ endpoint after enabling Ollama in configuration and setting the base URL to your
 Ollama server (default: `http://localhost:11434/v1`).
 
 ### Python
+
 ```python
 from openai import OpenAI
 
@@ -141,6 +146,35 @@ response = client.chat.completions.create(
     model="gpt-4o",
     messages=[{"role": "user", "content": "Hello!"}]
 )
+
+### Image Generation (DALL-E / Imagen)
+
+```python
+from openai import OpenAI
+
+client = OpenAI(
+    base_url="http://localhost:8080/v1",
+    api_key="YOUR_CLIENT_API_KEY"
+)
+
+# DALL-E 3 (OpenAI)
+resp = client.images.generate(
+    model="dall-e-3",
+    prompt="A cute gopher wearing a top hat",
+    n=1,
+    size="1024x1024"
+)
+print(resp.data[0].url)
+
+# Imagen 3 (Gemini) — uses same endpoint
+resp = client.images.generate(
+    model="imagen-3.0-generate-001",
+    prompt="A gopher coding in Go",
+    n=1,
+    size="1024x1024"
+)
+print(resp.data[0].url)  # Returns data URI (Gemini returns base64)
+```
 ```
 
 ## License

internal/models/models.go

@@ -210,6 +210,30 @@ func (i *ImageInput) ToBase64() (string, string, error) {
 	return "", "", fmt.Errorf("empty image input")
 }
 
+// Image Generation (DALL-E, Imagen)
+
+type ImageGenerationRequest struct {
+	Model          string  `json:"model"`
+	Prompt         string  `json:"prompt"`
+	N              *uint32 `json:"n,omitempty"`
+	Quality        *string `json:"quality,omitempty"`
+	ResponseFormat *string `json:"response_format,omitempty"`
+	Size           *string `json:"size,omitempty"`
+	Style          *string `json:"style,omitempty"`
+	User           *string `json:"user,omitempty"`
+}
+
+type ImageGenerationResponse struct {
+	Created int64       `json:"created"`
+	Data    []ImageData `json:"data"`
+}
+
+type ImageData struct {
+	URL           string `json:"url,omitempty"`
+	B64JSON       string `json:"b64_json,omitempty"`
+	RevisedPrompt string `json:"revised_prompt,omitempty"`
+}
+
 // AuthInfo for context
 type AuthInfo struct {
 	Token    string

internal/providers/circuit_breaker.go

@@ -54,3 +54,13 @@ func (cbp *CircuitBreakerProvider) ChatCompletionStream(ctx context.Context, req
 	// Future: Implement a way to track stream failures in the circuit breaker.
 	return cbp.provider.ChatCompletionStream(ctx, req)
 }
+
+func (cbp *CircuitBreakerProvider) ImageGeneration(ctx context.Context, req *models.ImageGenerationRequest) (*models.ImageGenerationResponse, error) {
+	result, err := cbp.cb.Execute(func() (interface{}, error) {
+		return cbp.provider.ImageGeneration(ctx, req)
+	})
+	if err != nil {
+		return nil, err
+	}
+	return result.(*models.ImageGenerationResponse), nil
+}

internal/providers/deepseek.go

@@ -3,15 +3,15 @@ package providers
 import (
 	"bufio"
 	"context"
-	"time"
 	"encoding/json"
 	"fmt"
 	"io"
 	"strings"
+	"time"
 
+	"github.com/go-resty/resty/v2"
 	"gophergate/internal/config"
 	"gophergate/internal/models"
-	"github.com/go-resty/resty/v2"
 )
 
 type DeepSeekProvider struct {
@@ -33,11 +33,11 @@ func (p *DeepSeekProvider) Name() string {
 }
 
 type deepSeekUsage struct {
-	PromptTokens          uint32 `json:"prompt_tokens"`
-	CompletionTokens      uint32 `json:"completion_tokens"`
-	TotalTokens           uint32 `json:"total_tokens"`
-	PromptCacheHitTokens  uint32 `json:"prompt_cache_hit_tokens"`
-	PromptCacheMissTokens uint32 `json:"prompt_cache_miss_tokens"`
+	PromptTokens            uint32 `json:"prompt_tokens"`
+	CompletionTokens        uint32 `json:"completion_tokens"`
+	TotalTokens             uint32 `json:"total_tokens"`
+	PromptCacheHitTokens    uint32 `json:"prompt_cache_hit_tokens"`
+	PromptCacheMissTokens   uint32 `json:"prompt_cache_miss_tokens"`
 	CompletionTokensDetails *struct {
 		ReasoningTokens uint32 `json:"reasoning_tokens"`
 	} `json:"completion_tokens_details"`
@@ -219,3 +219,7 @@ func StreamDeepSeek(ctx io.ReadCloser, ch chan<- *models.ChatCompletionStreamRes
 	}
 	return scanner.Err()
 }
+
+func (p *DeepSeekProvider) ImageGeneration(ctx context.Context, req *models.ImageGenerationRequest) (*models.ImageGenerationResponse, error) {
+	return nil, fmt.Errorf("deepseek does not support image generation")
+}

internal/providers/gemini.go

@@ -75,6 +75,116 @@ type GeminiFunctionResponse struct {
 	Response json.RawMessage `json:"response"`
 }
 
+func (p *GeminiProvider) ImageGeneration(ctx context.Context, req *models.ImageGenerationRequest) (*models.ImageGenerationResponse, error) {
+	// Gemini Imagen API: POST https://generativelanguage.googleapis.com/v1beta/models/{model}:predict
+	// Map OpenAI-style params to Gemini Imagen params
+
+	n := uint32(1)
+	if req.N != nil && *req.N > 0 {
+		n = *req.N
+	}
+
+	aspectRatio := "1:1"
+	if req.Size != nil {
+		aspectRatio = sizeToGeminiAspectRatio(*req.Size)
+	}
+
+	// Build Imagen request
+	imagenReq := map[string]interface{}{
+		"instances": []map[string]interface{}{
+			{"prompt": req.Prompt},
+		},
+		"parameters": map[string]interface{}{
+			"sampleCount": n,
+			"aspectRatio": aspectRatio,
+		},
+	}
+
+	// Model defaults to imagen-3.0-generate-001 if empty
+	model := req.Model
+	if model == "" {
+		model = "imagen-3.0-generate-001"
+	}
+
+	// Use v1beta for Imagen
+	baseURL := p.config.BaseURL
+	if !strings.Contains(baseURL, "v1beta") {
+		baseURL = strings.Replace(baseURL, "/v1", "/v1beta", 1)
+	}
+
+	url := fmt.Sprintf("%s/models/%s:predict?key=%s", baseURL, model, p.apiKey)
+
+	resp, err := p.client.R().
+		SetContext(ctx).
+		SetHeader("Content-Type", "application/json").
+		SetBody(imagenReq).
+		Post(url)
+
+	if err != nil {
+		return nil, fmt.Errorf("gemini imagen request failed: %w", err)
+	}
+
+	if !resp.IsSuccess() {
+		return nil, fmt.Errorf("Gemini Imagen API error (%d): %s", resp.StatusCode(), resp.String())
+	}
+
+	// Parse Imagen response
+	var imagenResp struct {
+		Predictions []struct {
+			MimeType           string `json:"mimeType"`
+			BytesBase64Encoded string `json:"bytesBase64Encoded"`
+		} `json:"predictions"`
+	}
+
+	if err := json.Unmarshal(resp.Body(), &imagenResp); err != nil {
+		return nil, fmt.Errorf("failed to parse Imagen response: %w", err)
+	}
+
+	respFormat := "url"
+	if req.ResponseFormat != nil && *req.ResponseFormat == "b64_json" {
+		respFormat = "b64_json"
+	}
+
+	var data []models.ImageData
+	for _, pred := range imagenResp.Predictions {
+		imgData := models.ImageData{}
+		if respFormat == "b64_json" {
+			imgData.B64JSON = pred.BytesBase64Encoded
+		} else {
+			// Build a data URI since Gemini returns base64, not a URL
+			mime := pred.MimeType
+			if mime == "" {
+				mime = "image/png"
+			}
+			imgData.URL = fmt.Sprintf("data:%s;base64,%s", mime, pred.BytesBase64Encoded)
+		}
+		data = append(data, imgData)
+	}
+
+	result := &models.ImageGenerationResponse{
+		Created: time.Now().Unix(),
+		Data:    data,
+	}
+
+	return result, nil
+}
+
+// sizeToGeminiAspectRatio converts OpenAI size format (e.g. "1024x1024") to Gemini aspect ratio (e.g. "1:1")
+func sizeToGeminiAspectRatio(size string) string {
+	switch size {
+	case "1024x1024":
+		return "1:1"
+	case "1024x1792":
+		return "9:16"
+	case "1792x1024":
+		return "16:9"
+	case "256x256", "512x512":
+		return "1:1"
+	default:
+		return "1:1"
+	}
+}
+
 func (p *GeminiProvider) ChatCompletion(ctx context.Context, req *models.UnifiedRequest) (*models.ChatCompletionResponse, error) {
 	// Gemini mapping
 	var contents []GeminiContent

internal/providers/grok.go

@@ -2,13 +2,13 @@ package providers
 
 import (
 	"context"
-	"time"
 	"encoding/json"
 	"fmt"
+	"time"
 
+	"github.com/go-resty/resty/v2"
 	"gophergate/internal/config"
 	"gophergate/internal/models"
-	"github.com/go-resty/resty/v2"
 )
 
 type GrokProvider struct {
@@ -94,3 +94,7 @@ func (p *GrokProvider) ChatCompletionStream(ctx context.Context, req *models.Uni
 
 	return ch, nil
 }
+
+func (p *GrokProvider) ImageGeneration(ctx context.Context, req *models.ImageGenerationRequest) (*models.ImageGenerationResponse, error) {
+	return nil, fmt.Errorf("grok does not support image generation")
+}

internal/providers/helpers.go

@@ -256,9 +256,10 @@ func StreamGemini(ctx io.ReadCloser, ch chan<- *models.ChatCompletionStreamRespo
 					FinishReason string `json:"finishReason"`
 				} `json:"candidates"`
 				UsageMetadata struct {
-					PromptTokenCount     uint32 `json:"promptTokenCount"`
-					CandidatesTokenCount uint32 `json:"candidatesTokenCount"`
-					TotalTokenCount      uint32 `json:"totalTokenCount"`
+					PromptTokenCount        uint32 `json:"promptTokenCount"`
+					CandidatesTokenCount    uint32 `json:"candidatesTokenCount"`
+					TotalTokenCount         uint32 `json:"totalTokenCount"`
+					CachedContentTokenCount uint32 `json:"cachedContentTokenCount"`
 				} `json:"usageMetadata"`
 			}
 

internal/providers/moonshot.go

@@ -2,14 +2,14 @@ package providers
 
 import (
 	"context"
-	"time"
 	"encoding/json"
 	"fmt"
 	"strings"
+	"time"
 
+	"github.com/go-resty/resty/v2"
 	"gophergate/internal/config"
 	"gophergate/internal/models"
-	"github.com/go-resty/resty/v2"
 )
 
 type MoonshotProvider struct {
@@ -113,3 +113,7 @@ func (p *MoonshotProvider) ChatCompletionStream(ctx context.Context, req *models
 
 	return ch, nil
 }
+
+func (p *MoonshotProvider) ImageGeneration(ctx context.Context, req *models.ImageGenerationRequest) (*models.ImageGenerationResponse, error) {
+	return nil, fmt.Errorf("moonshot does not support image generation")
+}

internal/providers/ollama.go

@@ -249,3 +249,7 @@ func StreamOllama(ctx io.ReadCloser, ch chan<- *models.ChatCompletionStreamRespo
 	}
 	return scanner.Err()
 }
+
+func (p *OllamaProvider) ImageGeneration(ctx context.Context, req *models.ImageGenerationRequest) (*models.ImageGenerationResponse, error) {
+	return nil, fmt.Errorf("ollama does not support image generation")
+}

internal/providers/openai.go

@@ -68,6 +68,53 @@ func (p *OpenAIProvider) ChatCompletion(ctx context.Context, req *models.Unified
 	return ParseOpenAIResponse(respJSON, req.Model)
 }
 
+func (p *OpenAIProvider) ImageGeneration(ctx context.Context, req *models.ImageGenerationRequest) (*models.ImageGenerationResponse, error) {
+	body := map[string]interface{}{
+		"prompt": req.Prompt,
+		"model":  req.Model,
+	}
+
+	if req.N != nil {
+		body["n"] = *req.N
+	}
+	if req.Quality != nil {
+		body["quality"] = *req.Quality
+	}
+	if req.ResponseFormat != nil {
+		body["response_format"] = *req.ResponseFormat
+	}
+	if req.Size != nil {
+		body["size"] = *req.Size
+	}
+	if req.Style != nil {
+		body["style"] = *req.Style
+	}
+	if req.User != nil {
+		body["user"] = *req.User
+	}
+
+	resp, err := p.client.R().
+		SetContext(ctx).
+		SetHeader("Authorization", "Bearer "+p.apiKey).
+		SetBody(body).
+		Post(fmt.Sprintf("%s/images/generations", p.config.BaseURL))
+
+	if err != nil {
+		return nil, fmt.Errorf("request failed: %w", err)
+	}
+
+	if !resp.IsSuccess() {
+		return nil, fmt.Errorf("OpenAI image API error (%d): %s", resp.StatusCode(), resp.String())
+	}
+
+	var result models.ImageGenerationResponse
+	if err := json.Unmarshal(resp.Body(), &result); err != nil {
+		return nil, fmt.Errorf("failed to parse response: %w", err)
+	}
+
+	return &result, nil
+}
+
 func (p *OpenAIProvider) ChatCompletionStream(ctx context.Context, req *models.UnifiedRequest) (<-chan *models.ChatCompletionStreamResponse, error) {
 	messagesJSON, err := MessagesToOpenAIJSON(req.Messages)
 	if err != nil {

internal/providers/provider.go

@@ -10,4 +10,5 @@ type Provider interface {
 	Name() string
 	ChatCompletion(ctx context.Context, req *models.UnifiedRequest) (*models.ChatCompletionResponse, error)
 	ChatCompletionStream(ctx context.Context, req *models.UnifiedRequest) (<-chan *models.ChatCompletionStreamResponse, error)
+	ImageGeneration(ctx context.Context, req *models.ImageGenerationRequest) (*models.ImageGenerationResponse, error)
 }

internal/server/server.go

@@ -186,6 +186,7 @@ func (s *Server) setupRoutes() {
 	v1.Use(middleware.AuthMiddleware(s.database, true))
 	{
 		v1.POST("/chat/completions", s.handleChatCompletions)
+		v1.POST("/images/generations", s.handleImageGenerations)
 		v1.GET("/models", s.handleListModels)
 		v1.GET("/responses", s.handleListResponses)
 	}
@@ -501,6 +502,71 @@ func (s *Server) handleChatCompletions(c *gin.Context) {
 	c.JSON(http.StatusOK, resp)
 }
 
+func (s *Server) handleImageGenerations(c *gin.Context) {
+	startTime := time.Now()
+	var req models.ImageGenerationRequest
+	if err := c.ShouldBindJSON(&req); err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
+		return
+	}
+
+	// Determine provider based on model name
+	providerName := "openai"
+	modelLower := strings.ToLower(req.Model)
+	switch {
+	case strings.Contains(modelLower, "imagen"), strings.Contains(modelLower, "gemini"):
+		providerName = "gemini"
+	case strings.Contains(modelLower, "dall"), strings.HasPrefix(modelLower, "openai/"):
+		providerName = "openai"
+	}
+
+	// Default model for each provider if not specified
+	if req.Model == "" {
+		if providerName == "openai" {
+			req.Model = "dall-e-3"
+		} else {
+			req.Model = "imagen-3.0-generate-001"
+		}
+	}
+
+	// Strip common prefixes
+	prefixes := []string{"openai/", "gemini/", "google/"}
+	for _, p := range prefixes {
+		if strings.HasPrefix(req.Model, p) {
+			req.Model = strings.TrimPrefix(req.Model, p)
+			break
+		}
+	}
+
+	provider, ok := s.providers[providerName]
+	if !ok {
+		c.JSON(http.StatusInternalServerError, gin.H{"error": fmt.Sprintf("Provider %s not enabled or supported", providerName)})
+		return
+	}
+
+	clientID := "default"
+	if auth, ok := c.Get("auth"); ok {
+		if authInfo, ok := auth.(models.AuthInfo); ok {
+			clientID = authInfo.ClientID
+		}
+	}
+
+	resp, err := provider.ImageGeneration(c.Request.Context(), &req)
+	if err != nil {
+		s.logRequest(startTime, clientID, providerName, req.Model, nil, err, false)
+		c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
+		return
+	}
+
+	s.logRequest(startTime, clientID, providerName, req.Model, &models.Usage{
+		PromptTokens:     1,
+		CompletionTokens: uint32(len(resp.Data)),
+		TotalTokens:      1 + uint32(len(resp.Data)),
+	}, nil, false)
+
+	c.JSON(http.StatusOK, resp)
+}
+
 func (s *Server) logRequest(start time.Time, clientID, provider, model string, usage *models.Usage, err error, hasImages bool) {
 	entry := RequestLog{
 		Timestamp:  start,