downkyicore/DownKyi/CustomControl/AsyncImageLoader/ImageBrushLoader.cs

using System;
using System.IO;
using Avalonia;
using Avalonia.Logging;
using Avalonia.Media;
using Avalonia.Media.Imaging;
using Avalonia.Threading;
using DownKyi.Core.Storage;
using DownKyi.CustomControl.AsyncImageLoader.Loaders;

namespace DownKyi.CustomControl.AsyncImageLoader;

public static class ImageBrushLoader
{
    private static readonly ParametrizedLogger? Logger;
    public static IAsyncImageLoader AsyncImageLoader { get; set; } = new DiskCachedWebImageLoader(Path.Combine(StorageManager.GetCache(), "Images"));

    static ImageBrushLoader()
    {
        SourceProperty.Changed.AddClassHandler<ImageBrush>(OnSourceChanged);
        Logger = Avalonia.Logging.Logger.TryGet(LogEventLevel.Error, ImageLoader.AsyncImageLoaderLogArea);
    }

    private static async void OnSourceChanged(ImageBrush imageBrush, AvaloniaPropertyChangedEventArgs args)
    {
        var (oldValue, newValue) = args.GetOldAndNewValue<string?>();
        if (oldValue == newValue)
            return;

        SetIsLoading(imageBrush, true);

        Bitmap? bitmap = null;
        try
        {
            if (newValue is not null)
            {
                // 注意缩放比例
                var width = GetWidth(imageBrush);
                var height = GetHeight(imageBrush);
                if (width > 0 && height > 0)
                {
                    var scale = await Dispatcher.UIThread.InvokeAsync(() => App.Current.MainWindow.DesktopScaling);
                    var actualWidth = Convert.ToInt32(width * scale);
                    var actualHeight = Convert.ToInt32(height * scale);
                    bitmap = (await AsyncImageLoader.ProvideImageAsync(newValue))?.CreateScaledBitmap(new PixelSize(actualWidth, actualHeight));
                }
                else
                {
                    bitmap = await AsyncImageLoader.ProvideImageAsync(newValue);
                }
            }
        }
        catch (Exception e)
        {
            Logger?.Log("ImageBrushLoader", "ImageBrushLoader image resolution failed: {0}", e);
        }

        if (GetSource(imageBrush) != newValue) return;
        imageBrush.Source = bitmap;

        SetIsLoading(imageBrush, false);
    }

    public static readonly AttachedProperty<string?> SourceProperty = AvaloniaProperty.RegisterAttached<ImageBrush, string?>("Source", typeof(ImageLoader));

    public static string? GetSource(ImageBrush element)
    {
        return element.GetValue(SourceProperty);
    }

    public static void SetSource(ImageBrush element, string? value)
    {
        element.SetValue(SourceProperty, value);
    }

    public static readonly AttachedProperty<bool> IsLoadingProperty = AvaloniaProperty.RegisterAttached<ImageBrush, bool>("IsLoading", typeof(ImageLoader));

    public static bool GetIsLoading(ImageBrush element)
    {
        return element.GetValue(IsLoadingProperty);
    }

    private static void SetIsLoading(ImageBrush element, bool value)
    {
        element.SetValue(IsLoadingProperty, value);
    }

    public static readonly AttachedProperty<int> WidthProperty = AvaloniaProperty.RegisterAttached<ImageBrush, int>("Width", typeof(ImageLoader));

    public static int GetWidth(ImageBrush element)
    {
        return element.GetValue(WidthProperty);
    }

    public static void SetWidth(ImageBrush element, int value)
    {
        element.SetValue(WidthProperty, value);
    }

    public static readonly AttachedProperty<int> HeightProperty = AvaloniaProperty.RegisterAttached<ImageBrush, int>("Height", typeof(ImageLoader));

    public static int GetHeight(ImageBrush element)
    {
        return element.GetValue(HeightProperty);
    }

    public static void SetHeight(ImageBrush element, int value)
    {
        element.SetValue(HeightProperty, value);
    }
}