VeloeAvaloniaKemonoPartyApplication/VeloeAvaloniaKemonoPartyApp/VeloeAvaloniaKemonoPartyApp/ViewModels/PostViewModel.cs

using Avalonia.Controls.ApplicationLifetimes;
using Avalonia.Media.Imaging;
using ReactiveUI;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using VeloeAvaloniaKemonoPartyApp.Models;

namespace VeloeAvaloniaKemonoPartyApp.ViewModels
{
    public class PostViewModel : ViewModelBase
    {
        private readonly Post _post;

        public PostViewModel(Post post)
        {
            _post = post;
        }

        public string Artist => _post.Content;

        public string Title => _post.Title;

        private Bitmap? _cover;

        public Bitmap? Cover
        {
            get => _cover;
            private set => this.RaiseAndSetIfChanged(ref _cover, value);
        }

        public async Task LoadAvatar()
        {
            if (_post.Attachments.Count == 0) return;

            await using (var imageStream = await _post.LoadCoverBitmapAsync())
            {
                Cover = await Task.Run(() =>
                {
                    Bitmap? bitmap;
                    try
                    {
                        bitmap = new Bitmap(imageStream);
                        bitmap = bitmap.CreateScaledBitmap(new Avalonia.PixelSize(bitmap.PixelSize.Width / 2, bitmap.PixelSize.Height / 2));
                    }
                    catch (Exception ex)
                    {
                        bitmap = null;
                    }
                    return bitmap;
                });
            }
        }

        public async Task SaveToDiskAsync()
        {
            await _post.SaveAsync();

            if (Cover != null)
            {
                var bitmap = Cover;

                await Task.Run(() =>
                {
                    using (var fs = _post.SaveCoverBitmapStream())
                    {
                        bitmap.Save(fs);
                    }
                });
            }
        }
    }
}