WPF坐标转换

前言

假如屏幕是1920*1080，缩放是125%；

那么WPF窗口最大设置为1536*864就会占满屏幕。

获取鼠标位置

获取的是屏幕实际像素对应的位置。

using System.Runtime.InteropServices;

namespace ColorPicker.Utils
{
    internal class ZPoint
    {
        [DllImport("user32.dll", CharSet = CharSet.Auto)]
        public static extern bool GetCursorPos(out POINT pt);

        [StructLayout(LayoutKind.Sequential)]
        public struct POINT
        {
            public int X;
            public int Y;

            public POINT(int x, int y)
            {
                this.X = x;
                this.Y = y;
            }
        }
    }
}

调用

ZPoint.POINT point;
ZPoint.GetCursorPos(out point);

这样获取的坐标是屏幕的实际尺寸算的，即1920*1080。

如果我们根据这个值设置WPF的窗口就会发生偏移。

像素坐标转换为WPF坐标

ZPoint.POINT point;
ZPoint.GetCursorPos(out point);
Matrix transform = PresentationSource.FromVisual(this).CompositionTarget.TransformFromDevice;
Point wpfPoint = transform.Transform(new System.Windows.Point(point.X, point.Y));

获取窗口的缩放率

using System;
using System.Drawing;
using System.Runtime.InteropServices;
using System.Runtime.Versioning;
using System.Windows;
using System.Windows.Forms;

namespace ColorPicker.Utils
{
    internal class ScreenHelper
    {

        private const string User32 = "user32.dll";

        [DllImport(User32, CharSet = CharSet.Auto)]
        [ResourceExposure(ResourceScope.None)]
        public static extern bool GetMonitorInfo(HandleRef hmonitor, [In, Out] MONITORINFOEX info);

        [DllImport(User32, ExactSpelling = true)]
        [ResourceExposure(ResourceScope.None)]
        public static extern bool EnumDisplayMonitors(HandleRef hdc, COMRECT rcClip, MonitorEnumProc lpfnEnum, IntPtr dwData);

        public delegate bool MonitorEnumProc(IntPtr monitor, IntPtr hdc, IntPtr lprcMonitor, IntPtr lParam);

        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto, Pack = 4)]
        public class MONITORINFOEX
        {
            internal int cbSize = Marshal.SizeOf(typeof(MONITORINFOEX));
            internal RECT rcMonitor = new RECT();
            internal RECT rcWork = new RECT();
            internal int dwFlags = 0;
            [MarshalAs(UnmanagedType.ByValArray, SizeConst = 32)]
            internal char[] szDevice = new char[32];
        }

        [StructLayout(LayoutKind.Sequential)]
        public struct RECT
        {
            public int left;
            public int top;
            public int right;
            public int bottom;

            public RECT(Rect r)
            {
                left = (int)r.Left;
                top = (int)r.Top;
                right = (int)r.Right;
                bottom = (int)r.Bottom;
            }
        }

        [StructLayout(LayoutKind.Sequential)]
        public class COMRECT
        {
            public int left;
            public int top;
            public int right;
            public int bottom;
        }

        public static readonly HandleRef NullHandleRef = new HandleRef(null, IntPtr.Zero);


        /// <summary>
        /// 获取缩放比例
        /// </summary>
        /// <returns></returns>
        public static double GetScalingRatio()
        {
            var logicalHeight = GetLogicalHeight();
            var actualHeight = GetActualHeight();

            if (logicalHeight > 0 && actualHeight > 0)
            {
                return logicalHeight / actualHeight;
            }

            return 1;
        }

        private static double GetActualHeight()
        {
            return SystemParameters.PrimaryScreenHeight;
        }

        private static double GetLogicalHeight()
        {
            var logicalHeight = 0.0;

           MonitorEnumProc proc = (m, h, lm, lp) =>
            {
                MONITORINFOEX info = new MONITORINFOEX();
                GetMonitorInfo(new HandleRef(null, m), info);

                //是否为主屏
                if ((info.dwFlags & 0x00000001) != 0)
                {
                    logicalHeight = info.rcMonitor.bottom - info.rcMonitor.top;
                }

                return true;
            };
            EnumDisplayMonitors(NullHandleRef, null, proc, IntPtr.Zero);

            return logicalHeight;
        }
    }
}

调用

ZPoint.POINT point;
ZPoint.GetCursorPos(out point);                   
var ScalingRatio = ScreenHelper.GetScalingRatio();
Console.WriteLine($"当前缩放比例为{ScalingRatio}%");
colorWin.Top = point.Y / ScalingRatio+4;
colorWin.Left = point.X / ScalingRatio+4;

这种作用和下面是一样的。

设置窗口在鼠标右下角

colorWin中添加如下方法

private void MoveBottomRightEdgeOfWindowToMousePosition()
{
    var transform = PresentationSource.FromVisual(this).CompositionTarget.TransformFromDevice;
    var mouse = transform.Transform(GetMousePosition());
    Left = mouse.X + 2;
    Top = mouse.Y - ActualHeight - 2;
}

public System.Windows.Point GetMousePosition()
{
    System.Drawing.Point point = System.Windows.Forms.Control.MousePosition;
    return new System.Windows.Point(point.X, point.Y);
}

更新位置

new Thread(o => {
    while (true) {
        Dispatcher.Invoke(
            () => 
            {
                if (Visibility == Visibility.Visible)
                {
                    MoveBottomRightEdgeOfWindowToMousePosition();
                }
            }
        );
        Thread.Sleep(10);
    }
})
{
    IsBackground = true
}.Start();