MARKUS

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

using System.Windows;

using System.Windows.Controls;

using System.Windows.Media;

using System.Windows.Media.Imaging;

namespace KCOM.Controls

{

    [TemplatePart(Name = PART_IMAGE, Type = typeof(Image))]

    public class ScaleDecodeImage : System.Windows.Controls.Control

    {

        private const string PART_IMAGE = "PART_IMAGE";

        private Image ImageControl;

        public override void OnApplyTemplate()

        {

            base.OnApplyTemplate();

            ImageControl = GetTemplateChild(PART_IMAGE) as Image;

        }

        public static readonly DependencyProperty SourceProperty = DependencyProperty.Register(

                    "Source", typeof(BitmapImage), typeof(ScaleDecodeImage),new PropertyMetadata(new PropertyChangedCallback(SourcePropertyChaged)));

        public BitmapImage Source

        {

            get => (BitmapImage)GetValue(SourceProperty);

            set => SetValue(SourceProperty, value);

        }

        private static void SourcePropertyChaged(DependencyObject d, DependencyPropertyChangedEventArgs e)

        {

            var owner = d as ScaleDecodeImage;

            if(owner != null)

            {

                owner.Scale = 1.0;

            }

        }

        public static readonly DependencyProperty ScaleProperty = DependencyProperty.Register(

                    "Scale", typeof(double), typeof(ScaleDecodeImage), new PropertyMetadata(0.0,new PropertyChangedCallback(ScalePropertyChaged)));

        public double Scale

        {

            get => (double)GetValue(ScaleProperty);

            set => SetValue(ScaleProperty, value);

        }

        private static async void ScalePropertyChaged(DependencyObject d, DependencyPropertyChangedEventArgs e)

        {

            var owner = d as ScaleDecodeImage;

            if (owner != null)

            {

                if(owner.ImageControl != null)

                {

                    var value = owner.Scale;

                    System.Windows.Media.Imaging.BitmapImage image = owner.Source.Clone();

                    image.DecodePixelWidth = (int)(image.PixelWidth * value);

                    image.DecodePixelHeight = (int)(image.PixelHeight * value);

                    await owner.Dispatcher.InvokeAsync(() => { owner.ImageControl.Source = image; });

                }

            }

        }

    }

}