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 ViewSourceProperty = DependencyProperty.Register(

                    "ViewSource", typeof(BitmapImage), typeof(ScaleDecodeImage));

        public BitmapImage ViewSource

        {

            get => (BitmapImage)GetValue(ViewSourceProperty);

            set => SetValue(ViewSourceProperty, value);

        }

        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)

            {

                if (e.NewValue != null)

                {

                    owner.ViewSource = (BitmapImage)e.NewValue;

                    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 void ScalePropertyChaged(DependencyObject d, DependencyPropertyChangedEventArgs e)

        {

            var owner = d as ScaleDecodeImage;

            if (owner != 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);

                owner.ViewSource = image;

            }

        }

    }

}