在C＃Windows窗體中繪制一條直線

Question

我有一個簡單的Windows窗體程序，該程序允許用戶在圖片框中繪制直線。 有一條線，但是它超出了圖片框，在其中不可見（就像我所附的圖片一樣）。 我怎樣才能使行僅出現在圖片框中。 這是我的代碼：

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

您可以創建一個與PictureBox大小相同的位圖，並在PictureBox的Paint事件中繪制該位圖。 然后在鼠標事件中繪制線條以繪制位圖。 這將在Windows中保留行以最小化/還原事件。 為了方便起見，我放置了整個代碼：

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);
    }
}