Add Gemini 3 Pro Image configuration support for Microsoft.Extensions.AI

src/GenerativeAI.Microsoft/AdditionalPropertyKeys.cs

@@ -24,4 +24,19 @@ public static class AdditionalPropertiesKeys
     /// Key used to specify the aspect ratio for image generation.
     /// </summary>
     public const string ImageConfigAspectRatio = "AspectRatio";
+
+    /// <summary>
+    /// Key used to specify the output resolution for image generation ("1K", "2K", "4K").
+    /// </summary>
+    public const string ImageConfigImageSize = "ImageSize";
+
+    /// <summary>
+    /// Key used to specify the output MIME type for image generation ("image/png", "image/jpeg").
+    /// </summary>
+    public const string ImageOutputOptionsMimeType = "MimeType";
+
+    /// <summary>
+    /// Key used to specify the compression quality for image generation (0-100).
+    /// </summary>
+    public const string ImageOutputOptionsCompressionQuality = "CompressionQuality";
 }

src/GenerativeAI.Microsoft/Extensions/MicrosoftExtensions.cs

@@ -348,6 +348,26 @@ private static JsonNode ToJsonNodeResponse(this object? response)
             config.ImageConfig.AspectRatio = aspectRatio;
         }
 
+        if (options.AdditionalProperties.TryGetValue(AdditionalPropertiesKeys.ImageConfigImageSize, out string? imageSize))
+        {
+            config.ImageConfig ??= new ImageConfig();
+            config.ImageConfig.ImageSize = imageSize;
+        }
+
+        if (options.AdditionalProperties.TryGetValue(AdditionalPropertiesKeys.ImageOutputOptionsMimeType, out string? mimeType))
+        {
+            config.ImageConfig ??= new ImageConfig();
+            config.ImageConfig.ImageOutputOptions ??= new ImageOutputOptions();
+            config.ImageConfig.ImageOutputOptions.MimeType = mimeType;
+        }
+
+        if (options.AdditionalProperties.TryGetValue(AdditionalPropertiesKeys.ImageOutputOptionsCompressionQuality, out int compressionQuality))
+        {
+            config.ImageConfig ??= new ImageConfig();
+            config.ImageConfig.ImageOutputOptions ??= new ImageOutputOptions();
+            config.ImageConfig.ImageOutputOptions.CompressionQuality = compressionQuality;
+        }
+
         return config;
     }
 

src/GenerativeAI/Constants/ImageConfigValues.cs

@@ -0,0 +1,59 @@
+namespace GenerativeAI;
+
+/// <summary>
+/// Provides common values for image generation configuration.
+/// These constants are provided for convenience and discoverability but are not restrictive;
+/// any valid string value accepted by the API can be used.
+/// </summary>
+/// <seealso href="https://ai.google.dev/gemini-api/docs/image-generation">See Official API Documentation</seealso>
+public static class ImageConfigValues
+{
+    /// <summary>
+    /// Common aspect ratios for image generation.
+    /// </summary>
+    public static class AspectRatios
+    {
+        /// <summary>Square aspect ratio (1:1).</summary>
+        public const string Square = "1:1";
+
+        /// <summary>Landscape aspect ratio (16:9), common for widescreen displays.</summary>
+        public const string Landscape16x9 = "16:9";
+
+        /// <summary>Portrait aspect ratio (9:16), common for mobile/vertical displays.</summary>
+        public const string Portrait9x16 = "9:16";
+
+        /// <summary>Landscape aspect ratio (4:3), traditional display format.</summary>
+        public const string Landscape4x3 = "4:3";
+
+        /// <summary>Portrait aspect ratio (3:4).</summary>
+        public const string Portrait3x4 = "3:4";
+    }
+
+    /// <summary>
+    /// Output resolutions for image generation.
+    /// Only supported on certain models like gemini-3-pro-image-preview.
+    /// </summary>
+    public static class ImageSizes
+    {
+        /// <summary>1K resolution output.</summary>
+        public const string Size1K = "1K";
+
+        /// <summary>2K resolution output.</summary>
+        public const string Size2K = "2K";
+
+        /// <summary>4K resolution output.</summary>
+        public const string Size4K = "4K";
+    }
+
+    /// <summary>
+    /// Output MIME types for generated images.
+    /// </summary>
+    public static class OutputMimeTypes
+    {
+        /// <summary>PNG format (lossless compression). This is the default.</summary>
+        public const string Png = "image/png";
+
+        /// <summary>JPEG format (lossy compression, supports compression quality setting).</summary>
+        public const string Jpeg = "image/jpeg";
+    }
+}

src/GenerativeAI/Types/ContentGeneration/Config/GenerationConfig.cs

@@ -165,7 +165,7 @@ public class GenerationConfig
     /// </summary>
     [JsonPropertyName("speechConfig")]
     public SpeechConfig? SpeechConfig { get; set; }
-    
+
     /// <summary>
     /// Optional. Config for thinking features.
     /// An error will be returned if this field is set for models that don't support thinking.
@@ -178,13 +178,13 @@ public class GenerationConfig
     /// </summary>
     [JsonPropertyName("mediaResolution")]
     public MediaResolution? MediaResolution { get; set; }
-    
+
     /// <summary>
     /// Optional. If enabled, audio timestamp will be included in the request to the model.
     /// </summary>
     [JsonPropertyName("audioTimestamp")]
     public bool? AudioTimestamp { get; set; }
-    
+
     /// <summary>
     /// Optional. Routing configuration.
     /// </summary>
@@ -228,7 +228,7 @@ public class ThinkingConfig
     /// </summary>
     [JsonPropertyName("includeThoughts")]
     public bool? IncludeThoughts { get; set; }
-    
+
     /// <summary>
     /// Indicates the thinking budget in tokens
     /// </summary>
@@ -279,7 +279,7 @@ public class RoutingConfig
 }
 
 /// <summary>
-/// When automated routing is specified, the routing will be determined by the pretrained routing model 
+/// When automated routing is specified, the routing will be determined by the pretrained routing model
 /// and customer provided model routing preference.
 /// </summary>
 public class AutoRoutingMode
@@ -329,14 +329,69 @@ public class ManualRoutingMode
     public string? ModelName { get; set; }
 }
 
-/// <summary>
-/// Configuration for image generation in models that support image output (e.g., gemini-2.5-flash-image).
-/// </summary>
-public class ImageConfig
-{
-    /// <summary>
-    /// Optional. The aspect ratio for generated images. Common values: "16:9", "9:16", "1:1", "4:3", "3:4".
-    /// </summary>
-    [JsonPropertyName("aspectRatio")]
-    public string? AspectRatio { get; set; }
-}
+  /// <summary>
+  /// Configuration for image generation in models that support image output (e.g., gemini-2.5-flash-image, gemini-3-pro-image-preview).
+  /// </summary>
+  /// <remarks>
+  /// Use <see cref="ImageConfigValues"/> for common predefined values.
+  /// </remarks>
+  /// <seealso href="https://ai.google.dev/gemini-api/docs/image-generation">See Official API Documentation</seealso>
+  public class ImageConfig
+  {
+      /// <summary>
+      /// Optional. The aspect ratio for generated images.
+      /// </summary>
+      /// <remarks>
+      /// Common values include "1:1" (square), "16:9" (landscape), "9:16" (portrait), "4:3", and "3:4".
+      /// See <see cref="ImageConfigValues.AspectRatios"/> for predefined constants.
+      /// </remarks>
+      [JsonPropertyName("aspectRatio")]
+      public string? AspectRatio { get; set; }
+
+      /// <summary>
+      /// Optional. The output resolution for generated images.
+      /// </summary>
+      /// <remarks>
+      /// Values: "1K", "2K", "4K". Only supported on certain models like gemini-3-pro-image-preview.
+      /// See <see cref="ImageConfigValues.ImageSizes"/> for predefined constants.
+      /// </remarks>
+      [JsonPropertyName("imageSize")]
+      public string? ImageSize { get; set; }
+
+      /// <summary>
+      /// Optional. The image output options for generated images.
+      /// </summary>
+      /// <remarks>
+      /// Only supported on certain models like gemini-3-pro-image-preview.
+      /// </remarks>
+      [JsonPropertyName("imageOutputOptions")]
+      public ImageOutputOptions? ImageOutputOptions { get; set; }
+  }
+
+  /// <summary>
+  /// The image output format for generated images.
+  /// </summary>
+  /// <remarks>
+  /// See <see cref="ImageConfigValues.OutputMimeTypes"/> for predefined MIME type constants.
+  /// </remarks>
+  public class ImageOutputOptions
+  {
+      /// <summary>
+      /// Optional. The image format that the output should be saved as.
+      /// </summary>
+      /// <remarks>
+      /// Default is "image/png". Supported values: "image/png", "image/jpeg".
+      /// See <see cref="ImageConfigValues.OutputMimeTypes"/> for predefined constants.
+      /// </remarks>
+      [JsonPropertyName("mimeType")]
+      public string? MimeType { get; set; }
+
+      /// <summary>
+      /// Optional. The compression quality of the output image (0-100).
+      /// </summary>
+      /// <remarks>
+      /// Only applicable when <see cref="MimeType"/> is "image/jpeg". Default is 75.
+      /// </remarks>
+      [JsonPropertyName("compressionQuality")]
+      public int? CompressionQuality { get; set; }
+  }

src/GenerativeAI/Types/TypesSerializerContext.cs

@@ -20,6 +20,8 @@ namespace GenerativeAI.Types;
 [JsonSerializable(typeof(GoogleTypeDate))]
 [JsonSerializable(typeof(Schema))]
 [JsonSerializable(typeof(GenerationConfig))]
+[JsonSerializable(typeof(ImageConfig))]
+[JsonSerializable(typeof(ImageOutputOptions))]
 [JsonSerializable(typeof(ModelSelectionConfig))]
 [JsonSerializable(typeof(FeatureSelectionPreference))]
 [JsonSerializable(typeof(PrebuiltVoiceConfig))]