magic-selfie

Magic Selfie Sample

This sample is part of the AI Sample Catalog. To build and run this sample, you should clone the entire repository.

Description

This sample demonstrates how to create a "magic selfie" by replacing the background of a user's photo with a generated image. It uses the Nano Banana 2 (gemini-3.1-flash-image-preview) model to perform semantic image editing, transforming the background based on a text prompt while preserving the subject.

How it works

The application uses the Firebase AI SDK (see How to run) for Android to interact with the Nano Banana 2 model. Unlike older approaches that require manual subject segmentation and image compositing, Nano Banana 2 can process a multimodal prompt (an image plus text) to modify the scene directly. The application sends the user's selfie and a prompt describing the desired background, and the model generates a new version of the image with the background replaced. The core logic for this process is in the MagicSelfieViewModel.kt and MagicSelfieRepository.kt files.

Here is the key snippet of code that calls the generative model from MagicSelfieRepository.kt:

suspend fun generateMagicSelfie(bitmap: Bitmap, prompt: String): Bitmap {
    val multimodalPrompt = content {
        image(bitmap)
        text("Change the background of this image to $prompt")
    }
    val response = generativeModel.generateContent(multimodalPrompt)
    return response.candidates.firstOrNull()?.content?.parts?.firstNotNullOfOrNull { it.asImageOrNull() }
        ?: throw Exception("No image generated")
}

Read more about the Gemini API in the Android Documentation.