1.效果展示

代码

        /// <summary>
        /// 记录鼠标移动时的位置
        /// </summary>
        private Point _mouseLocation;

        //鼠标移动事件
        private void pic_1_MouseMove(object sender, MouseEventArgs e)
        {
            _mouseLocation = e.Location;
            pic_1.Refresh();
        }

        //绘图事件
        private void pic_1_Paint(object sender, PaintEventArgs e)
        {
            var pic = (PictureBox)sender;

            //定义两个点
            var points = new Point[2];
            points[0] = new Point(101, 43);
            points[1] = new Point(548, 536);
            var x1 = points[0].X;
            var y1 = points[0].Y;
            var x2 = points[1].X;
            var y2 = points[1].Y;

            //定义两个画笔
            var brush = new SolidBrush(Color.FromArgb(127, Color.Black));
            var pen = new Pen(Brushes.Brown, 3);

            e.Graphics.Clear(Color.SkyBlue);//清除整个绘图面并以指定背景色填充

            #region [绘制一张图像]
            var bmp = (Bitmap)Image.FromFile(Application.StartupPath + @"\猫咪.jpg", false); //从指定路径获取一张Bitmap
            var rectBmpPos = new Rectangle();//获取图像显示的位置和宽、高信息
            //取 PictureBox和Bitmap 的宽高比
            var picByBmpScale = Math.Min((float)pic.Width / bmp.Width, (float)pic.Height / bmp.Height);
            rectBmpPos.Width = (int)(bmp.Width * picByBmpScale);
            rectBmpPos.Height = (int)(bmp.Height * picByBmpScale);
            rectBmpPos.X = (pic.Width - rectBmpPos.Width) / 2;
            rectBmpPos.Y = (pic.Height - rectBmpPos.Height) / 2;
            var rectBmpSize = new Rectangle(0, 0, bmp.Width, bmp.Height);//图像显示的区域

            e.Graphics.SmoothingMode = SmoothingMode.HighQuality;//指定抗锯齿的呈现
            e.Graphics.DrawImage(bmp, rectBmpPos, rectBmpSize, GraphicsUnit.Pixel);//绘制图像
            bmp.Dispose();
            #endregion [绘制一张图像]


            #region [画一条线段，端点处以椭圆代表点]
            e.Graphics.FillEllipse(brush, x1 - 3, y1 - 3, 6, 6);//绘制一个椭圆，填充内部颜色，可以代表一个点
            e.Graphics.FillEllipse(brush, x2 - 3, y2 - 3, 6, 6);//绘制一个椭圆，填充内部颜色，可以代表一个点
            e.Graphics.DrawLine(pen, x1, y1, x2, y2);//绘制一条直线 
            #endregion [画一条线段，端点处以椭圆代表点]


            #region [绘制一个矩形框]
            if (x1 > x2)
            {
                x1 = x1 + x2;
                x2 = x1 - x2;
                x1 = x1 - x2;
            }
            if (y1 > y2)
            {
                y1 = y1 + y2;
                y2 = y1 - y2;
                y1 = y1 - y2;
            }
            e.Graphics.DrawRectangle(pen, x1, y1, x2 - x1, y2 - y1);
            #endregion [绘制一个矩形框]


            #region [当前鼠标所在位置绘制十字交叉线，并输出坐标信息]
            e.Graphics.DrawLine(pen, _mouseLocation.X, 0, _mouseLocation.X, pic.Height);//绘制垂直条
            e.Graphics.DrawLine(pen, 0, _mouseLocation.Y, pic.Width + 200, _mouseLocation.Y);//绘制水平线条
            string strLoc = $"({_mouseLocation.X},{_mouseLocation.Y})";
            Font font = new Font("Arial", 12f, FontStyle.Bold);
            SizeF selPtStrSize = e.Graphics.MeasureString(strLoc, font);//文字的宽高
            var strPoint = _mouseLocation;

            if (strPoint.X > pic.Width / 2 && strPoint.Y < pic.Height / 2)//右上角
            {
                strPoint.X -= (int)selPtStrSize.Width;
            }
            else if (strPoint.X > pic.Width / 2 && strPoint.Y > pic.Height / 2)//右下角
            {
                strPoint.X -= (int)selPtStrSize.Width;
                strPoint.Y -= (int)selPtStrSize.Height;
            }
            else if (strPoint.X < pic.Width / 2 && strPoint.Y > pic.Height / 2)//左下角
            {
                strPoint.Y -= (int)selPtStrSize.Height;
            }
            e.Graphics.DrawString(strLoc, font, new SolidBrush(Color.Black), strPoint);//绘制文字
            #endregion [当前鼠标所在位置绘制十字交叉线，并输出坐标信息]

        }