Create images using Stable Diffusion API from C#

AvatarCreateService.cs

using System;
using System.Net.Http;
using System.Text;
using System.Text.Json;
using System.Threading;
using System.Threading.Tasks;

namespace SimpleAvatarGenerator
{
    /// <summary>
    /// Represents the response from the avatar generation API.
    /// </summary>
    public class AvatarCreateResponse
    {
        public string AvatarId { get; set; } = Guid.NewGuid().ToString();
        public string Prompt { get; set; } = string.Empty;
        public string ImageBase64 { get; set; } = string.Empty;
    }

    /// <summary>
    /// Simple service for generating images from prompts using an API.
    /// </summary>
    public class AvatarCreateService
    {
        private const string ApiUrl = "http://127.0.0.1:7860";
        private const string Text2ImageEndpoint = "/sdapi/v1/txt2img";

        /// <summary>
        /// Generates an image from the given prompt.
        /// </summary>
        /// <param name="prompt">The text prompt for image generation.</param>
        /// <param name="negativePrompt">The negative prompt to guide generation.</param>
        /// <param name="removeBackground">Whether to remove the background.</param>
        /// <param name="ct">Cancellation token.</param>
        /// <returns>The avatar response with base64 image.</returns>
        public async Task<AvatarCreateResponse> GenerateImageAsync(
            string prompt,
            string negativePrompt,
            bool removeBackground = true,
            CancellationToken ct = default)
        {
            using var client = new HttpClient();

            // Build the JSON payload
            var requestJson = new
            {
                prompt = prompt,
                negative_prompt = negativePrompt,
                steps = 20,
                model = "dreamshaper_8",
                script_name = removeBackground ? "ABG Remover" : string.Empty,
                script_args = removeBackground ? new object[] { true, false, "", "FFFFFF", false } : null
            };

            var content = new StringContent(
                JsonSerializer.Serialize(requestJson),
                Encoding.UTF8,
                "application/json"
            );

            var response = await client.PostAsync($"{ApiUrl}{Text2ImageEndpoint}", content, ct);

            response.EnsureSuccessStatusCode();

            var responseBody = await response.Content.ReadAsStringAsync(ct);
            var jsonResponse = JsonDocument.Parse(responseBody);

            var base64Image = jsonResponse.RootElement
                                        .GetProperty("images")[0]
                                        .GetString();

            if (string.IsNullOrEmpty(base64Image))
                throw new Exception("No image returned from API.");

            return new AvatarCreateResponse
            {
                Prompt = prompt,
                ImageBase64 = base64Image
            };
        }
    }
}