Dispenser/DispenserUI/Views/Controls/ROISelector.cs

using System;
using Avalonia;
using Avalonia.Controls;
using Avalonia.Controls.Shapes;
using Avalonia.Input;
using Avalonia.Media;

namespace DispenserUI.Views.Controls;

public class ROISelector : Canvas
{
    public static readonly StyledProperty<Point> ROICenterProperty =
        AvaloniaProperty.Register<ROISelector, Point>(nameof(ROICenter));

    private Path centerPath;
    private EllipseGeometry circle;
    private Point circleCenter;
    private Path circlePath;
    private Point currentPoint;
    private bool isDragging;
    private bool isMouseDragged;
    private bool isDrawingComplete;
    private bool isPositionChangeable;
    private bool isRadiusChangeable;

    public Point ROICenter
    {
        get => GetValue(ROICenterProperty);
        set => SetValue(ROICenterProperty, value);
    }

    public ROISelector()
    {
        this.GetObservable(ROICenterProperty).Subscribe(val =>
        {
            DrawROI();
        });
    }
    
    private double Get2PointsDistance(Point firstPoint, Point secondPoint)
    {
        return Math.Pow(Math.Pow(secondPoint.X - firstPoint.X, 2) + Math.Pow(secondPoint.Y - firstPoint.Y, 2), 0.5);
    }

    public new void OnPointerPressed(PointerPressedEventArgs e)
    {
        var pointerPoint = e.GetCurrentPoint(this);
        //鼠标左键按下
        if (pointerPoint.Properties.PointerUpdateKind == PointerUpdateKind.LeftButtonPressed)
        {
            isDragging = true; //开启拖动
            //未绘制ROI区域，可以开始绘制
            if (isDrawingComplete == false)
            {
                circleCenter = e.GetPosition(this);
            }
            //已经绘制ROI区域，可以修改区域
            else
            {
                currentPoint = e.GetPosition(this);
                var distance = Get2PointsDistance(currentPoint, circleCenter);

                //点击圆内位置，移动圆位置
                if (distance < circle.RadiusX)
                    isPositionChangeable = true;
                //点击圆外30像素以内位置，改变圆半径
                else if (distance > circle.RadiusX && distance < circle.RadiusX + 30) isRadiusChangeable = true;
            }
        }

        e.Handled = false;
    }

    public new void OnPointerReleased(PointerReleasedEventArgs e)
    {
        var pointerPoint = e.GetCurrentPoint(this);
        // 鼠标左键释放：结束绘制
        if (pointerPoint.Properties.PointerUpdateKind == PointerUpdateKind.LeftButtonReleased)
        {
            isDragging = false; //结束拖动
            if (isMouseDragged == true)
            {
                isDrawingComplete = true; //绘制完成
                isMouseDragged = false;
            }

            isRadiusChangeable = false;
            isPositionChangeable = false;
        }
        //鼠标右键释放:确定数据，清除图像
        else if (pointerPoint.Properties.PointerUpdateKind == PointerUpdateKind.RightButtonReleased)
        {
            isPositionChangeable = false;
            isRadiusChangeable = false;
            isDrawingComplete = false;
            Children.Remove(circlePath);
            ROICenter = new Point(circleCenter.X, circleCenter.Y);
        }

        e.Handled = false;
    }

    public new void OnPointerMoved(PointerEventArgs e)
    {
        if (isDragging == false) return;
        isMouseDragged = true;
        currentPoint = e.GetPosition(this);
        DrawROI();
        e.Handled = false;
    }


    private void DrawROI()
    {
        Children.Remove(circlePath);
        Children.Remove(centerPath);
        //绘制ROI
        if (isDrawingComplete == false)
        {
            var radius = Get2PointsDistance(currentPoint, circleCenter);
            DrawCircle(circleCenter, radius);
        }
        else if (isPositionChangeable)
        {
            var radius = circle.RadiusX;
            circleCenter = currentPoint;
            DrawCircle(circleCenter, radius);
        }
        else if (isRadiusChangeable)
        {
            var radius = Get2PointsDistance(currentPoint, circleCenter);
            DrawCircle(circleCenter, radius);
        }

        Children.Add(circlePath);
        Children.Add(centerPath);
    }

    private void DrawCircle(Point center, double radius)
    {
        circle = new EllipseGeometry
        {
            Center = center,
            RadiusX = radius,
            RadiusY = radius
        };
        circlePath = new Path
        {
            Data = circle,
            Stroke = Brushes.Orange,
            StrokeThickness = 2
        };
        var centerPoint = new EllipseGeometry
        {
            Center = center,
            RadiusX = 2,
            RadiusY = 2,
        };
        centerPath = new Path
        {
            Data = centerPoint,
            Stroke = Brushes.Orange,
            Fill = Brushes.Orange,
            StrokeThickness = 2
        };
    }
}