Add Vertex Imagen image generation service

Introduce support for Google Vertex Imagen image generation: add VertexImageGenService to call Vertex AI predict endpoints (uses service account token, default model/location, decodes base64 image into ChatResult), register BackendType.Vertex in ImageGenServiceFactory, add model constant (Imagen4_0_Generate) and CloudModel record (VertexImagen4_0Generate). Also adjust Home.razor injections and minor backendKey formatting. Includes basic response/error handling and model name extraction for publisher prefixes.

Author: Madzionator

src/MaIN.Domain/Models/Concrete/CloudModels.cs

@@ -132,6 +132,13 @@ public sealed record VertexVeo2_0Generate() : CloudModel(
     4000,
     "Google's video generation model available through Vertex AI"), IImageGenerationModel;
 
+public sealed record VertexImagen4_0Generate() : CloudModel(
+    Models.Vertex.Imagen4_0_Generate,
+    BackendType.Vertex,
+    "Imagen 4.0 (Vertex)",
+    4000,
+    "Google's latest image generation model available through Vertex AI"), IImageGenerationModel;
+
 // ===== xAI Models =====
 
 public sealed record Grok3Beta() : CloudModel(

src/MaIN.Domain/Models/Models.cs

@@ -55,6 +55,7 @@ public static class Vertex
         public const string Gemini2_5Pro = "google/gemini-2.5-pro";
         public const string Gemini2_5Flash = "google/gemini-2.5-flash";
         public const string Veo2_0_Generate = "google/veo-2.0-generate-001";
+        public const string Imagen4_0_Generate = "google/imagen-4.0-generate-001";
     }
 
     public static class Local

src/MaIN.InferPage/Components/Pages/Home.razor

@@ -3,7 +3,7 @@
 @inject IJSRuntime JS
 @inject SettingsService SettingsStorage
 @inject SettingsStateService SettingsState
-@inject MaIN.Domain.Configuration.MaINSettings MaINSettings
+@inject MaINSettings MaINSettings
 @implements IDisposable
 @using MaIN.Core.Hub
 @using MaIN.Core.Hub.Contexts.Interfaces.ChatContext
@@ -427,9 +427,12 @@
         if (backendType != BackendType.Self)
         {
             var backendKey = backendType == BackendType.Ollama
-                ? (settings.IsOllamaCloud ? "OllamaCloud" : "OllamaLocal")
-                : backendType == BackendType.Vertex ? "Vertex"
-                : backendType.ToString();
+                ? (settings.IsOllamaCloud 
+                    ? "OllamaCloud" 
+                    : "OllamaLocal")
+                : backendType == BackendType.Vertex 
+                    ? "Vertex"
+                    : backendType.ToString();
 
             apiKey = await SettingsStorage.GetApiKeyForBackendAsync(backendKey);
         }

src/MaIN.Services/Services/ImageGenServices/VertexImageGenService.cs

@@ -0,0 +1,118 @@
+using MaIN.Domain.Configuration;
+using MaIN.Domain.Configuration.BackendInferenceParams;
+using MaIN.Domain.Entities;
+using MaIN.Services.Constants;
+using MaIN.Services.Services.Abstract;
+using MaIN.Services.Services.LLMService.Auth;
+using MaIN.Services.Services.Models;
+using System.Net.Http.Headers;
+using System.Net.Http.Json;
+using System.Text.Json.Serialization;
+
+namespace MaIN.Services.Services.ImageGenServices;
+
+internal class VertexImageGenService(IHttpClientFactory httpClientFactory, MaINSettings settings) : IImageGenService
+{
+    private const string DefaultModel = "imagen-4.0-generate-001";
+    private const string DefaultLocation = "us-central1";
+
+    public async Task<ChatResult?> Send(Chat chat)
+    {
+        var auth = settings.GoogleServiceAccountAuth
+                   ?? throw new InvalidOperationException("Vertex AI service account is not configured.");
+
+        var location = chat.BackendParams is VertexInferenceParams vp
+            ? vp.Location
+            : DefaultLocation;
+
+        using var tokenProvider = new GoogleServiceAccountTokenProvider(auth);
+        var httpClient = httpClientFactory.CreateClient(ServiceConstants.HttpClients.VertexClient);
+        var accessToken = await tokenProvider.GetAccessTokenAsync(httpClient);
+
+        var model = ExtractModelName(chat.ModelId);
+        var endpoint = $"https://{location}-aiplatform.googleapis.com/v1/projects/{auth.ProjectId}/locations/{location}/publishers/google/models/{model}:predict";
+
+        var requestBody = new
+        {
+            instances = new[]
+            {
+                new { prompt = BuildPromptFromChat(chat) }
+            },
+            parameters = new
+            {
+                sampleCount = 1,
+                aspectRatio = "1:1"
+            }
+        };
+
+        using var request = new HttpRequestMessage(HttpMethod.Post, endpoint);
+        request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", accessToken);
+        request.Content = JsonContent.Create(requestBody);
+
+        using var response = await httpClient.SendAsync(request);
+
+        if (!response.IsSuccessStatusCode)
+        {
+            var error = await response.Content.ReadAsStringAsync();
+            throw new InvalidOperationException(
+                $"Vertex AI Imagen request failed ({response.StatusCode}): {error}");
+        }
+
+        var result = await response.Content.ReadFromJsonAsync<ImagenResponse>();
+        var base64Image = result?.Predictions?.FirstOrDefault()?.BytesBase64Encoded;
+
+        if (string.IsNullOrEmpty(base64Image))
+            throw new InvalidOperationException("No image returned from Vertex AI Imagen.");
+
+        var imageBytes = Convert.FromBase64String(base64Image);
+
+        return new ChatResult
+        {
+            Done = true,
+            Message = new Message
+            {
+                Content = ServiceConstants.Messages.GeneratedImageContent,
+                Role = ServiceConstants.Roles.Assistant,
+                Image = imageBytes,
+                Type = MessageType.Image
+            },
+            Model = chat.ModelId ?? $"google/{DefaultModel}",
+            CreatedAt = DateTime.UtcNow
+        };
+    }
+
+    private static string BuildPromptFromChat(Chat chat)
+    {
+        return chat.Messages
+            .Select((msg, index) => index == 0 ? msg.Content : $"&& {msg.Content}")
+            .Aggregate((current, next) => $"{current} {next}");
+    }
+
+    /// <summary>
+    /// Strips the "google/" publisher prefix if present (Vertex predict endpoint doesn't use it).
+    /// </summary>
+    private static string ExtractModelName(string? modelId)
+    {
+        if (string.IsNullOrEmpty(modelId))
+            return DefaultModel;
+
+        return modelId.StartsWith("google/", StringComparison.OrdinalIgnoreCase)
+            ? modelId["google/".Length..]
+            : modelId;
+    }
+}
+
+file class ImagenResponse
+{
+    [JsonPropertyName("predictions")]
+    public ImagenPrediction[]? Predictions { get; set; }
+}
+
+file class ImagenPrediction
+{
+    [JsonPropertyName("bytesBase64Encoded")]
+    public string? BytesBase64Encoded { get; set; }
+
+    [JsonPropertyName("mimeType")]
+    public string? MimeType { get; set; }
+}

src/MaIN.Services/Services/LLMService/Factory/ImageGenServiceFactory.cs

@@ -20,11 +20,11 @@ public class ImageGenServiceFactory(IServiceProvider serviceProvider) : IImageGe
             BackendType.Anthropic => null,
             BackendType.Xai => new XaiImageGenService(serviceProvider.GetRequiredService<IHttpClientFactory>(),
                 serviceProvider.GetRequiredService<MaINSettings>()),
+            BackendType.Vertex => new VertexImageGenService(serviceProvider.GetRequiredService<IHttpClientFactory>(),
+                serviceProvider.GetRequiredService<MaINSettings>()),
             BackendType.Ollama => null,
             BackendType.Self => new ImageGenService(serviceProvider.GetRequiredService<IHttpClientFactory>(),
                 serviceProvider.GetRequiredService<MaINSettings>()),
-            
-            // Add other backends as needed
             _ => throw new NotSupportedException("Not support image generation."),
         };
     }