WPF: Kolor pod wskaźnikiem

Question

Mam kontrolę z gradiant tle. Na zdarzeniu MouseDown lub MouseUp chcę uchwycić, jaki kolor piksel znajduje się pod wskaźnikiem myszy. Jak to zrobić?

Answer 1

Stworzyłem zachowanie, które można dołączyć do obiektu obrazu, aby pobrać kolor, który jest 100% WPF. Oto zachowanie; może być zmodyfikowany do pracy z dowolnym "obrazem", a nie tylko obrazem.

[Uwaga: Mam ustalony 96 dpi do tworzenia RenderTargetBitmap ... Twój przebieg mogą się różnić]

using System.ComponentModel; 
using System.Windows; 
using System.Windows.Controls; 
using System.Windows.Input; 
using System.Windows.Interactivity; 
using System.Windows.Media; 
using System.Windows.Media.Imaging; 

namespace Company.Solution.Project.Utilities.Behaviors 
{ 
    [Description("Used to sample the color under mouse for the image when the mouse is pressed. ")] 
    public class ImageBehaviorMouseDownPointSampleToColor : Behavior<Image> 
    { 
     public static readonly DependencyProperty SelectedColorProperty = 
      DependencyProperty.Register("SelectedColor", typeof(Color), 
             typeof(ImageBehaviorMouseDownPointSampleToColor), 
             new UIPropertyMetadata(Colors.White)); 


     public Color SelectedColor 
     { 
      get { return (Color)GetValue(SelectedColorProperty); } 
      set { SetValue(SelectedColorProperty, value); } 
     } 


     protected override void OnAttached() 
     { 
      base.OnAttached(); 

      AssociatedObject.MouseMove += AssociatedObject_MouseMove; 
      AssociatedObject.MouseDown += AssociatedObject_MouseDown; 
     } 

     protected override void OnDetaching() 
     { 
      base.OnDetaching(); 

      AssociatedObject.MouseMove -= AssociatedObject_MouseMove; 
      AssociatedObject.MouseDown -= AssociatedObject_MouseDown; 
     } 

     private void AssociatedObject_MouseDown(object sender, MouseButtonEventArgs e) 
     { 
      SamplePixelForColor(); 
     } 

     private void AssociatedObject_MouseMove(object sender, MouseEventArgs e) 
     { 
      if (e.LeftButton == MouseButtonState.Pressed) 
      { 
       SamplePixelForColor(); 
      } 
     } 

     private void SamplePixelForColor() 
     { 
      // Retrieve the coordinate of the mouse position in relation to the supplied image. 
      Point point = Mouse.GetPosition(AssociatedObject); 

      // Use RenderTargetBitmap to get the visual, in case the image has been transformed. 
      var renderTargetBitmap = new RenderTargetBitmap((int)AssociatedObject.ActualWidth, 
                  (int)AssociatedObject.ActualHeight, 
                  96, 96, PixelFormats.Default); 
      renderTargetBitmap.Render(AssociatedObject); 

      // Make sure that the point is within the dimensions of the image. 
      if ((point.X <= renderTargetBitmap.PixelWidth) && (point.Y <= renderTargetBitmap.PixelHeight)) 
      { 
       // Create a cropped image at the supplied point coordinates. 
       var croppedBitmap = new CroppedBitmap(renderTargetBitmap, 
                 new Int32Rect((int)point.X, (int)point.Y, 1, 1)); 

       // Copy the sampled pixel to a byte array. 
       var pixels = new byte[4]; 
       croppedBitmap.CopyPixels(pixels, 4, 0); 

       // Assign the sampled color to a SolidColorBrush and return as conversion. 
       SelectedColor = Color.FromArgb(255, pixels[2], pixels[1], pixels[0]); 
      } 
     }   
     }   
    }