Question

我用这种方式在图片框中划一条线：

horizontalstart = new Point(0, e.Y); //Start point of Horizontal line.
horizontalend = new Point(picbox_mpr.Width, e.Y); //End point of Horizontal line.
verticalstart = new Point(e.X, 0); //Start point of Vertical line
verticalend = new Point(e.X, picbox_mpr.Height); //End point of Vertical line.

然后在绘画事件上我这样做：

e.Graphics.DrawLine(redline, horizontalstart, horizontalend); //Draw Horizontal line.
e.Graphics.DrawLine(redline, verticalstart, verticalend); //Draw Vertical line.

非常简单，现在，我的图像可以放大，这就是我挣扎的地方..

即使缩放图像，如何将线条保持在绘制的相同位置？

Answer 1

不是存储绝对整数坐标，而是存储一个十进制值，表示该坐标相对于图像宽度/高度的“百分比”。因此，如果X值为10且宽度为100，则存储0.1。假设图像被缩放，现在已经变宽了300。 0.1现在可以转换为0.1 * 300 = 30.您可以在PointF（）而不是Point（）中存储“百分比”X，Y对。

以下是一个简单的例子：

public partial class Form1 : Form
{

    private List<Tuple<PointF, PointF>> Points = new List<Tuple<PointF, PointF>>();

    public Form1()
    {
        InitializeComponent();
        this.Shown += new EventHandler(Form1_Shown);

        this.pictureBox1.BackColor = Color.Red;
        this.pictureBox1.SizeChanged += new EventHandler(pictureBox1_SizeChanged);
        this.pictureBox1.Paint += new PaintEventHandler(pictureBox1_Paint);
    }

    void Form1_Shown(object sender, EventArgs e)
    {
        // convert absolute points:
        Point ptStart = new Point(100, 25);
        Point ptEnd = new Point(300, 75);

        // to percentages:
        PointF ptFstart = new PointF((float)ptStart.X / (float)pictureBox1.Width, (float)ptStart.Y / (float)pictureBox1.Height);
        PointF ptFend = new PointF((float)ptEnd.X / (float)pictureBox1.Width, (float)ptEnd.Y / (float)pictureBox1.Height);

        // add the percentage point to our list:
        Points.Add(new Tuple<PointF, PointF>(ptFstart, ptFend));
        pictureBox1.Refresh();
    }

    private void button1_Click(object sender, EventArgs e)
    {
        // increase the size of the picturebox 
        // watch how the line(s) change with the changed picturebox
        pictureBox1.Size = new Size(pictureBox1.Width + 50, pictureBox1.Height + 50);
    }

    void pictureBox1_SizeChanged(object sender, EventArgs e)
    {
        pictureBox1.Refresh();
    }

    void pictureBox1_Paint(object sender, PaintEventArgs e)
    {
        foreach (Tuple<PointF, PointF> tup in Points)
        {
            // convert the percentages back to absolute coord based on the current size:
            Point ptStart = new Point((int)(tup.Item1.X * pictureBox1.Width), (int)(tup.Item1.Y * pictureBox1.Height));
            Point ptEnd = new Point((int)(tup.Item2.X * pictureBox1.Width), (int)(tup.Item2.Y * pictureBox1.Height));
            e.Graphics.DrawLine(Pens.Black, ptStart, ptEnd);
        }
    }

}

在图片框中绘制线条并在缩放时重绘

1 个答案: