如何防止pictureBox图像在移动时被拖曳？

Question

你好stackoverflow社区。我已经尝试寻找类似的问题，但我只找到关于闪烁的问题，这与我遇到的问题不同。

当我在面板上移动PictureBoxes时，我需要帮助防止它们被拖到后面。我正在制作的应用程序类似于MS Paint。当我单击PictureBox时，我可以使用以下命令单击并拖动它：

private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
{            
    x = e.X;
    y = e.Y;
}

private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
{
    if (e.Button == MouseButtons.Left)
    {
        pictureBox1.Left += (e.X - x);
        pictureBox1.Top += (e.Y - y);
    }
}

和其他我没有点击的pictureBoxes被绘制到DoubleBuffered面板上，使用：

private void panel1_Paint(object sender, PaintEventArgs e)
{
    foreach (PictureBox pb in pboxes)
    {
        if (!pb.Visible)
        {
            e.Graphics.DrawImage(pb.BackgroundImage, new Rectangle(pb.Location, pb.Size));
        }
    }
}

由于某些原因，当我拖动PictureBox时，它的背景图像会在绘制的面板上拖动。

奇怪的是，这只发生在Paint事件上。如果我让面板的背景图像有一些东西，移动的PictureBox将不会跟踪。只有当我在面板上绘制Images时才会发生这种情况。

下面是一个例子

​

如果有任何帮助，我将不胜感激，谢谢。

我简化了代码以便更容易理解(仍然会产生拖尾效应)。

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

namespace WindowsFormsApplication1

{

public partial class Form1 : Form
{

    int x;
    int y;

    public Form1()
    {
        InitializeComponent();
        pictureBox1.Show();
        pictureBox2.Hide();
        pictureBox3.Hide();
    }

    private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
    {            
        x = e.X;
        y = e.Y;
        panel1.Invalidate();
    }

    private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
    {
        if (e.Button == MouseButtons.Left)
        {
            pictureBox1.Left += (e.X - x);
            pictureBox1.Top += (e.Y - y);
        }
    }

    private void panel1_Paint(object sender, PaintEventArgs e)
    {
        e.Graphics.DrawImage(pictureBox2.BackgroundImage, new Rectangle(pictureBox2.Location, pictureBox2.Size));
        e.Graphics.DrawImage(pictureBox3.BackgroundImage, new Rectangle(pictureBox3.Location, pictureBox3.Size));
    }


}}

它使用这个doubleBuffered面板类

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace WindowsFormsApplication1
{
    public class DoubleBufferPanel : Panel
    {


        public DoubleBufferPanel()
        {

            // Set the value of the double-buffering style bits to true.
            this.DoubleBuffered = true;



            this.SetStyle(ControlStyles.DoubleBuffer | ControlStyles.UserPaint |
             ControlStyles.AllPaintingInWmPaint, true);

            this.UpdateStyles();

        }


    }

}

现在我的代码需要3个PictureBox和1个DoubleBuffered面板。

表格是最大化的，Panel1.size = (2000, 1200);和each PictureBox size = (700, 700)，并将每个PictureBoxes背景图像设置为随机的大细节图像。当我移动pictureBox1时，拖尾效果就会出现，我每次都可以重现这个效果。

Answer 1

您是否尝试过从OnPaint处理程序调用基类的OnPaint，或者从MouseMove中选择性地执行无效/刷新？

Answer 2

我知道这是几年前的事了，但今天我也遇到了类似的麻烦。我正在单击并拖动一个用于放大图像部分的PictureBox。通过获得正确的操作顺序解决了这些问题:大小、移动、绘制。我通过以下方式解决了这个问题：

1. 在窗体的Load event

期间实例化PictureBox

1. 在MouseMove event

期间使用Location属性重新定位MouseMove

在

1. Invalidating

之后重新定位PictureBox

通过Invalidate()触发的事件期间的

1. 重绘

1. 我为我的PictureBox设置了一个自定义形状(Region)，它是在VisibleChange事件期间设置的。*

仅当按下鼠标左键且图像足够大时，

1. PictureBox才可见(Visible == true)。*

*=可选的

以下是我的代码中经过修改的摘录。我希望它们足够相关。

public Form1()
{
    InitializeComponent();

    this.Paint += new System.Windows.Forms.PaintEventHandler(Form1_Paint);
    Main_PictureBox.Paint += new PaintEventHandler(Main_PictureBox_Paint);
    Main_PictureBox.MouseDown += new MouseEventHandler(StartZoom);
    Zoom_PictureBox.MouseDown += new MouseEventHandler(StartZoom);
    Main_PictureBox.MouseMove += new MouseEventHandler(MoveZoom);
    Main_PictureBox.MouseUp += new MouseEventHandler(EndZoom);
    Main_PictureBox.MouseLeave += new EventHandler(EndZoom);
    Zoom_PictureBox.MouseUp += new MouseEventHandler(EndZoom);
    Zoom_PictureBox.VisibleChanged += new EventHandler(Zoom_PictureBox_VisibleRegion);
    Zoom_PictureBox.Paint += new PaintEventHandler(Zoom_PictureBox_Paint);
}
private void Form1_Paint(object sender, PaintEventArgs e)
{
    int H = flowLayoutPanel1.Height - flowLayoutPanel1.Margin.Size.Height;
    Main_PictureBox.MinimumSize = new Size(0, 0);
    Main_PictureBox.MaximumSize = new Size(flowLayoutPanel1.Width, H);
}
private void Main_PictureBox_Paint(object sender, PaintEventArgs e)
{
    Main_PictureBox.Parent.MaximumSize = Main_PictureBox.Size + Main_PictureBox.Margin.Size;
}
private void DisplayImage(object sender, EventArgs e)
{
    Image img = ((PictureBox)sender).Image;

    int W = img.Width;
    int H = img.Height;
    float ratio = (float)W / (float)H;

    Main_PictureBox.Image = img;
    Main_PictureBox.Size = new Size(W, H);
    float TestRatio = ((float)Main_PictureBox.Width / (float)Main_PictureBox.Height);
    if (TestRatio < ratio)
        Main_PictureBox.Height = (int)((float)Main_PictureBox.Width / ratio);
    else if (TestRatio > ratio)
        Main_PictureBox.Width = (int)((float)Main_PictureBox.Height * ratio);
}
private void Zoom_PictureBox_VisibleRegion(object sender, EventArgs e)
{
    using (var gp = new System.Drawing.Drawing2D.GraphicsPath())
    {
        gp.AddEllipse(new Rectangle(0, 0, this.Zoom_PictureBox.Width, this.Zoom_PictureBox.Height));
        this.Zoom_PictureBox.Region = new Region(gp);
    }
}
private void Zoom_PictureBox_Paint(object sender, PaintEventArgs e)
{
    e.Graphics.DrawImage(Main_PictureBox.Image, e.ClipRectangle, cropRectangle, GraphicsUnit.Pixel);
}
private void StartZoom(object sender, MouseEventArgs e)
{
    if (e.Button == MouseButtons.Left && scale > 1.25)
    {
        int dX = Zoom_PictureBox.Width / 2;
        int dY = Zoom_PictureBox.Height / 2;
        Zoom_PictureBox.Visible = true;
        Zoom_PictureBox.Location = new Point(e.X - dX, e.Y - dY);
    }
}
private void MoveZoom(object sender, MouseEventArgs e)
{
    if (Main_PictureBox.Image != null)
    {
        Zoom_PictureBox.Visible = (e.Button == MouseButtons.Left && scale > 1.25);
        if (Zoom_PictureBox.Visible && e.Button == MouseButtons.Left)
        {
            int dX = Zoom_PictureBox.Width / 2;
            int dY = Zoom_PictureBox.Height / 2;

            Zoom_PictureBox.Location = new Point(e.X - dX, e.Y - dY);
            Zoom_PictureBox.Invalidate();
        }
    }
}
private void EndZoom(object sender, MouseEventArgs e)
{
    if (e.Button == MouseButtons.Left)
        EndZoom();
}
private void EndZoom(object sender, EventArgs e)
{
    EndZoom();
}
private void EndZoom()
{
    Zoom_PictureBox.Visible = false;
}
private Rectangle cropRectangle
{
    get
    {
        if (Main_PictureBox.Image != null)
        {
            Point origin = Main_PictureBox.PointToScreen(new Point(0, 0));
            float X = (float)(MousePosition.X - origin.X);
            return new Rectangle(
                (int)(scale * X) - Zoom_PictureBox.Width / 2,
                (int)(scale * (float)(MousePosition.Y - origin.Y)) - Zoom_PictureBox.Height / 2,
                Zoom_PictureBox.Width,
                Zoom_PictureBox.Height);
        }
        else
            return new Rectangle();
    }
}
private float scale
{
    get
    {
        if (Main_PictureBox.Image != null)
            return (float)Main_PictureBox.Image.Height / (float)Main_PictureBox.Height;
        else
            return 0;
    }
}