Improve imagen Java API (#6712)

- Make the `ImagenGenerationConfig.Builder` follow the builder pattern
- Mark companion object `ImagenImageFormat` methods as @JvmStatic for
easier access

Author: rlazo

firebase-vertexai/api.txt

@@ -428,6 +428,11 @@ package com.google.firebase.vertexai.type {
   public static final class ImagenGenerationConfig.Builder {
     ctor public ImagenGenerationConfig.Builder();
     method public com.google.firebase.vertexai.type.ImagenGenerationConfig build();
+    method public com.google.firebase.vertexai.type.ImagenGenerationConfig.Builder setAddWatermark(boolean addWatermark);
+    method public com.google.firebase.vertexai.type.ImagenGenerationConfig.Builder setAspectRatio(com.google.firebase.vertexai.type.ImagenAspectRatio aspectRatio);
+    method public com.google.firebase.vertexai.type.ImagenGenerationConfig.Builder setImageFormat(com.google.firebase.vertexai.type.ImagenImageFormat imageFormat);
+    method public com.google.firebase.vertexai.type.ImagenGenerationConfig.Builder setNegativePrompt(String negativePrompt);
+    method public com.google.firebase.vertexai.type.ImagenGenerationConfig.Builder setNumberOfImages(int numberOfImages);
     field public Boolean? addWatermark;
     field public com.google.firebase.vertexai.type.ImagenAspectRatio? aspectRatio;
     field public com.google.firebase.vertexai.type.ImagenImageFormat? imageFormat;
@@ -441,6 +446,7 @@ package com.google.firebase.vertexai.type {
 
   public final class ImagenGenerationConfigKt {
     method @com.google.firebase.vertexai.type.PublicPreviewAPI public static com.google.firebase.vertexai.type.ImagenGenerationConfig imagenGenerationConfig(kotlin.jvm.functions.Function1<? super com.google.firebase.vertexai.type.ImagenGenerationConfig.Builder,kotlin.Unit> init);
+    method public static void xx();
   }
 
   @com.google.firebase.vertexai.type.PublicPreviewAPI public final class ImagenGenerationResponse<T> {
@@ -453,6 +459,8 @@ package com.google.firebase.vertexai.type {
   @com.google.firebase.vertexai.type.PublicPreviewAPI public final class ImagenImageFormat {
     method public Integer? getCompressionQuality();
     method public String getMimeType();
+    method public static com.google.firebase.vertexai.type.ImagenImageFormat jpeg(Integer? compressionQuality = null);
+    method public static com.google.firebase.vertexai.type.ImagenImageFormat png();
     property public final Integer? compressionQuality;
     property public final String mimeType;
     field public static final com.google.firebase.vertexai.type.ImagenImageFormat.Companion Companion;

firebase-vertexai/src/main/kotlin/com/google/firebase/vertexai/type/ImagenGenerationConfig.kt

@@ -26,6 +26,8 @@ package com.google.firebase.vertexai.type
  * @param imageFormat The file format/compression of the generated images.
  * @param addWatermark Adds an invisible watermark to mark the image as AI generated.
  */
+import kotlin.jvm.JvmField
+
 @PublicPreviewAPI
 public class ImagenGenerationConfig(
   public val negativePrompt: String? = null,
@@ -39,13 +41,6 @@ public class ImagenGenerationConfig(
    *
    * This is mainly intended for Java interop. For Kotlin, use [imagenGenerationConfig] for a more
    * idiomatic experience.
-   *
-   * @property negativePrompt See [ImagenGenerationConfig.negativePrompt].
-   * @property numberOfImages See [ImagenGenerationConfig.numberOfImages].
-   * @property aspectRatio See [ImagenGenerationConfig.aspectRatio].
-   * @property imageFormat See [ImagenGenerationConfig.imageFormat]
-   * @property addWatermark See [ImagenGenerationConfig.addWatermark]
-   * @see [imagenGenerationConfig]
    */
   public class Builder {
     @JvmField public var negativePrompt: String? = null
@@ -54,6 +49,31 @@ public class ImagenGenerationConfig(
     @JvmField public var imageFormat: ImagenImageFormat? = null
     @JvmField public var addWatermark: Boolean? = null
 
+    /** See [ImagenGenerationConfig.negativePrompt]. */
+    public fun setNegativePrompt(negativePrompt: String): Builder = apply {
+      this.negativePrompt = negativePrompt
+    }
+
+    /** See [ImagenGenerationConfig.numberOfImages]. */
+    public fun setNumberOfImages(numberOfImages: Int): Builder = apply {
+      this.numberOfImages = numberOfImages
+    }
+
+    /** See [ImagenGenerationConfig.aspectRatio]. */
+    public fun setAspectRatio(aspectRatio: ImagenAspectRatio): Builder = apply {
+      this.aspectRatio = aspectRatio
+    }
+
+    /** See [ImagenGenerationConfig.imageFormat]. */
+    public fun setImageFormat(imageFormat: ImagenImageFormat): Builder = apply {
+      this.imageFormat = imageFormat
+    }
+
+    /** See [ImagenGenerationConfig.addWatermark]. */
+    public fun setAddWatermark(addWatermark: Boolean): Builder = apply {
+      this.addWatermark = addWatermark
+    }
+
     /**
      * Alternative casing for [ImagenGenerationConfig.Builder]:
      * ```
@@ -97,3 +117,14 @@ public fun imagenGenerationConfig(
   builder.init()
   return builder.build()
 }
+
+@OptIn(PublicPreviewAPI::class)
+public fun xx() {
+  imagenGenerationConfig {
+    negativePrompt = "People, black and white, painting"
+    numberOfImages = 1
+    aspectRatio = ImagenAspectRatio.SQUARE_1x1
+    imageFormat = ImagenImageFormat.png()
+    addWatermark = false
+  }
+}

firebase-vertexai/src/main/kotlin/com/google/firebase/vertexai/type/ImagenImageFormat.kt

@@ -41,11 +41,13 @@ private constructor(public val mimeType: String, public val compressionQuality:
      * @param compressionQuality an int (1-100) representing the quality of the image; a lower
      * number means the image is permitted to be lower quality to reduce size.
      */
+    @JvmStatic
     public fun jpeg(compressionQuality: Int? = null): ImagenImageFormat {
       return ImagenImageFormat("image/jpeg", compressionQuality)
     }
 
     /** An [ImagenImageFormat] representing a PNG image */
+    @JvmStatic
     public fun png(): ImagenImageFormat {
       return ImagenImageFormat("image/png", null)
     }