在C＃窗体中绘制一条直线

Question

我有一个简单的Windows窗体程序，允许用户在图片框中绘制直线。有一条线，但它从图片框中出来并且在其中不可见（如我附上的图片）。我怎样才能使它只显示在图片框中。这是我的代码：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Windows.Input;

namespace LinePOD
{
public partial class LineTest : Form
{
    public LineTest()
    {
        InitializeComponent();
    }

    Point p1 = new Point();
    Point p2 = new Point();
    Pen pen = new Pen(Color.Magenta, 10);
    private void LineTest_Load(object sender, EventArgs e)
    {

    }

    private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
    {
        if (e.Button == MouseButtons.Left)
            p1 = e.Location;
    }

    private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
    {

        if (e.Button == MouseButtons.Left)
        {
            p2 = e.Location;
            Graphics g = this.CreateGraphics();
            g.DrawLine(pen, p1, p2);
        }
    }

    private void pictureBox1_Click(object sender, EventArgs e)
    {

    }

    private void button1_Click(object sender, EventArgs e)
    {
        pictureBox1.BackColor = Color.Aqua;
    }
}

}

Answer 1

您可以创建具有相同大小的PictureBox的位图，并在PictureBox的Paint事件中绘制该位图。然后在鼠标事件中绘制线条到位图。这将保留Windows中最小化/恢复事件的行。我把整个代码放在方便之处：

public partial class Form1 : Form
{
    Bitmap bitmap;

    public Form1()
    {
        InitializeComponent();
    }

    private void Form1_Load(object sender, EventArgs e)
    {
        bitmap = new Bitmap(pictureBox1.ClientSize.Width, 
        pictureBox1.ClientSize.Height, 
        System.Drawing.Imaging.PixelFormat.Format32bppArgb);

    }

    Point p1 = new Point();
    Point p2 = new Point();
    Pen pen = new Pen(Color.Magenta, 10);

    private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
    {
        if (e.Button == MouseButtons.Left)
            p1 = e.Location;
    }

    private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
    {

        if (e.Button == MouseButtons.Left)
        {
            p2 = e.Location;
            Graphics g = Graphics.FromImage(bitmap);
            g.DrawLine(pen, p1, p2);
            pictureBox1.Invalidate();
            g.Dispose();
        }
    }

    private void button1_Click(object sender, EventArgs e)
    {
        pictureBox1.BackColor = Color.Aqua;
    }

    private void pictureBox1_Paint(object sender, PaintEventArgs e)
    {
        e.Graphics.DrawImage(bitmap, 0, 0, bitmap.Width, bitmap.Height);
    }
}