How can you send an image to the server using the Retrofit library?

To send an image to the server using Retrofit, a multipart request is usually used. The image is transmitted as part of a form with the type MultipartBody.Part. Example:

// API interface
public interface ApiService {
    @Multipart
    @POST("upload")
    Call<ResponseBody> uploadImage(@Part MultipartBody.Part image);
}

// Preparing the file and creating MultipartBody.Part
File file = new File("path/to/image.jpg");
RequestBody requestFile = RequestBody.create(MediaType.parse("image/jpeg"), file);
MultipartBody.Part body = MultipartBody.Part.createFormData("image", file.getName(), requestFile);

// Calling the API
ApiService service = retrofit.create(ApiService.class);
Call<ResponseBody> call = service.uploadImage(body);
call.enqueue(new Callback<ResponseBody>() {
    @Override
    public void onResponse(Call<ResponseBody> call, Response<ResponseBody> response) {
        // handle successful response
    }

    @Override
    public void onFailure(Call<ResponseBody> call, Throwable t) {
        // handle error
    }
});

This approach allows you to send a file as part of a multipart/form-data request, which is often required for uploading images to a server.