feat: Add support for enhance_prompt to model.generate_image

PiperOrigin-RevId: 719466587

Author: sasha-gitg

src/main/java/com/google/genai/Models.java

@@ -1581,6 +1581,13 @@ ObjectNode GenerateImagesConfigToMldev(
           Common.getValueByPath(fromObject, new String[] {"aspectRatio"}));
     }
 
+    if (Common.getValueByPath(fromObject, new String[] {"enhancePrompt"}) != null) {
+      Common.setValueByPath(
+          parentObject,
+          new String[] {"parameters", "enhancePrompt"},
+          Common.getValueByPath(fromObject, new String[] {"enhancePrompt"}));
+    }
+
     return toObject;
   }
 
@@ -1686,6 +1693,13 @@ ObjectNode GenerateImagesConfigToVertex(
           Common.getValueByPath(fromObject, new String[] {"aspectRatio"}));
     }
 
+    if (Common.getValueByPath(fromObject, new String[] {"enhancePrompt"}) != null) {
+      Common.setValueByPath(
+          parentObject,
+          new String[] {"parameters", "enhancePrompt"},
+          Common.getValueByPath(fromObject, new String[] {"enhancePrompt"}));
+    }
+
     return toObject;
   }
 

src/main/java/com/google/genai/types/GenerateImagesConfig.java

@@ -62,6 +62,9 @@ public abstract class GenerateImagesConfig extends JsonSerializable {
   /** Aspect ratio of the generated images. */
   public abstract Optional<String> getAspectRatio();
 
+  /** Whether to use the prompt rewriting logic. */
+  public abstract Optional<Boolean> getEnhancePrompt();
+
   /** Instantiates a builder for GenerateImagesConfig. */
   public static Builder builder() {
     return new AutoValue_GenerateImagesConfig.Builder();
@@ -115,6 +118,9 @@ public abstract static class Builder {
     @JsonProperty("aspectRatio")
     public abstract Builder setAspectRatio(String aspectRatio);
 
+    @JsonProperty("enhancePrompt")
+    public abstract Builder setEnhancePrompt(boolean enhancePrompt);
+
     public abstract GenerateImagesConfig build();
   }