如何删除表单上的绘制线？ [英] How to delete a drawn line on a form?

问题描述

其实这里有一些类似的问题，但我看不到答案是什么。

例如，我在Windows上绘制了2行代码表单和我想删除其中一个并保留其他，我该怎么做？

this.Invalidate（）; 或 Graphics.Clear（）; 清除所有表格，我不想要这个，我想删除特定行。你还有其他的解决方案吗？

b
$ b

 图形g; 
 Pen p; 
位图bmp; 
列表< Point> Lines = new List< Point>（）; 
 
 private void Form2_Load（object sender，EventArgs e）
 {
 bmp = new Bitmap（Width，Height，System.Drawing.Imaging.PixelFormat.Format24bppRgb）; 
 BackgroundImage = bmp; 
 g = Graphics.FromImage（BackgroundImage）; 
 g.Clear（Color.DeepSkyBlue）; //这是我们的backcolor 
} 
 
 private void btnLine1_Click（object sender，EventArgs e）
 {
 Point A = new Point（50，50）; 
 B点=新点（100,50）; 
 p =新笔（Color.Red）; 
 g.DrawLine（p，A，B）; //使用任何方法绘制线条
 Lines.Add（A）; //抓住第一点;添加到列表
 Lines.Add（B）; //抓住第二点;添加到列表
 Refresh（）; //刷新绘图到位图。 
} 
 
 private void btnDrawLine2_Click（object sender，EventArgs e）
 {
 Point A = new Point（50，60）; 
 B点=新点（100，60）; 
 p =新笔（Color.White）; 
 g.DrawLine（p，A，B）; //同上面的逻辑
 Lines.Add（A）; 
 Lines.Add（B）; 
 Refresh（）; 
} 
 
 private void btnUndo_Click（object sender，EventArgs e）
 {
 c = new Pen（Color.DeepSkyBlue）; 
 r =新笔（lastColor.ElementAt（lastColor.Count  -  2））; 
尝试
 {
 g.DrawLine（c，Lines.ElementAt（Lines.Count  -  2），Lines.ElementAt（Lines.Count  -  1））; 
 Lines.RemoveAt（Lines.Count  -  2）; 
 Lines.RemoveAt（Lines.Count  -  1）; 
 for（int i = Lines.Count; i> 0; i--）
 {
 g.DrawLine（r，Lines.ElementAt（Lines.Count  -  2），Lines。 ElementAt（Lines.Count  -  1））; 
} 
} 
 catch {} 
 Refresh（）; 
} 
  

以下是两行并排：

*请记得处理您的图形对象！

Actually there are some similar questions about this topic but I couldn't see the answer what I am looking for.

For example I have drawn 2 lines on windows form and I want to delete one of them and keep the other, how can I do that?

this.Invalidate(); or Graphics.Clear(); clear all the form, I don't want this, I want to delete specific line. Do you have any other solutions?

解决方案

The following will delete the all created lines in reverse chronological sequence.

    Graphics g;
    Pen p;
    Bitmap bmp;
    List<Point> Lines = new List<Point>();

    private void Form2_Load(object sender, EventArgs e)
    {
        bmp = new Bitmap(Width, Height, System.Drawing.Imaging.PixelFormat.Format24bppRgb);
        BackgroundImage = bmp;
        g = Graphics.FromImage(BackgroundImage);
        g.Clear(Color.DeepSkyBlue); //This is our backcolor
    }

    private void btnLine1_Click(object sender, EventArgs e)
    {
        Point A = new Point(50, 50);
        Point B = new Point(100, 50);
        p = new Pen(Color.Red);
        g.DrawLine(p, A, B); //Use whatever method to draw your line
        Lines.Add(A); //Grab the first point; add to list
        Lines.Add(B); //Grab the second point; add to list
        Refresh(); //Refresh drawing to bitmap.
    }

    private void btnDrawLine2_Click(object sender, EventArgs e)
    {
        Point A = new Point(50, 60);
        Point B = new Point(100, 60);
        p = new Pen(Color.White);
        g.DrawLine(p, A, B); //Same logic as above
        Lines.Add(A);
        Lines.Add(B);
        Refresh();
    }

    private void btnUndo_Click(object sender, EventArgs e)
    {
        c = new Pen(Color.DeepSkyBlue);
        r = new Pen(lastColor.ElementAt(lastColor.Count - 2));
        try
        {
            g.DrawLine(c, Lines.ElementAt(Lines.Count - 2), Lines.ElementAt(Lines.Count - 1));
            Lines.RemoveAt(Lines.Count - 2);
            Lines.RemoveAt(Lines.Count - 1);
            for (int i = Lines.Count; i > 0; i--)
            {
            g.DrawLine(r, Lines.ElementAt(Lines.Count - 2), Lines.ElementAt(Lines.Count - 1));
            }
        }
        catch { }
        Refresh();
    }

Here's 2 lines side by side:

Here's 2 lines overlapping:

*Remember to dispose your graphics objects!

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