计算一条线的精确像素 [英] Calculating Exact Pixels for a line

问题描述

说我想尽力做成一条直线，尽管可以有任何角度

Say i want to try to make a straight line albeit with any angle

public class Line : Control
{
    public Point start { get; set; }
    public Point end { get; set; }
    public Pen pen = new Pen(Color.Red);

    protected override void OnPaint(PaintEventArgs e)
    {
        e.Graphics.DrawLine(pen, start, end);
        base.OnPaint(e);
    }
}

此行已在自定义控件上进行.

This line has been made on a custom control.

现在我该如何计算精确的像素，以便可以使用 MouseMove 进行命中测试.

Now how can i calculate the exact pixels on which the line has been made so i can implement a hit test with MouseMove.

推荐答案

有Win32调用，用于枚举将使用GDI调用绘制的线条的像素.我相信这是您要完成的最佳技术.请参见 LineDDA 及其关联的回调

There are Win32 calls for enumerating the pixels of a line that would be drawn using GDI calls. I believe this is the best technique for what you're trying to accomplish. See LineDDA and its associated callback LineDDAProc.

这是在C#中使用它的方式.请注意，根据LineDDA的文档，终点不包括在输出中.

Here's how you would use it from C#. Note that the end point is not included in the output, as per the documentation of LineDDA.

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Runtime.InteropServices;

public static List<Point> GetPointsOnLine(Point point1, Point point2)
{
    var points = new List<Point>();
    var handle = GCHandle.Alloc(points);
    try
    {
        LineDDA(point1.X, point1.Y, point2.X, point2.Y, GetPointsOnLineCallback, GCHandle.ToIntPtr(handle));
    }
    finally
    {
        handle.Free();
    }
    return points;
}

private static void GetPointsOnLineCallback(int x, int y, IntPtr lpData)
{
    var handle = GCHandle.FromIntPtr(lpData);
    var points = (List<Point>) handle.Target;
    points.Add(new Point(x, y));
}

[DllImport("gdi32.dll")]
private static extern bool LineDDA(int nXStart, int nYStart, int nXEnd, int nYEnd, LineDDAProc lpLineFunc, IntPtr lpData);

// The signature for the callback method
private delegate void LineDDAProc(int x, int y, IntPtr lpData);

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