像在画图板里实现鼠标按下选择起点，鼠标移到哪，图形画到哪

Question

我现在要实现类似Windows中画图板的功能，现在遇到一个问题，就是鼠标按下，选择起点，在鼠标移动的过程中，去除旧框，再画新框，可是用什么绘图模式除去呢？求教啊！

Answer 1

在mouseup事件下处理先进行定位,再进行重绘.不用除去,因为重绘了.

Answer 2

我知道在MouseUp事件里捕捉起点，但是需要的是鼠标移动到哪，图形就绘制到哪，我在MouseOver事件里画图，但是之前鼠标移动过的位置画出的图形都会保留在哪，这是不希望的。

Answer 3

不要放到paint事件里，paint只用来初始化图片，图片的处理要用自己定义的paintMethod在需要是绘制。。
代码稍等

Answer 4

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Data.Common;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using BPOSuperSQLClass;
using SystemHotKey;
using System.Drawing.Drawing2D;
using System.Threading;
using BPOSYSTEM.myClass;
using System.IO;
using System.Collections;
using System.Reflection;namespace BPOSYSTEM
{
    public partial class InputForm : Form
    {
        #region property
        private Bitmap srcImage;
        private Bitmap toDrawBeffor;
        private Graphics gOfToDrawBeffor;
        private Graphics gOfbuff;
        private BufferedGraphicsContext ctx;
        private BufferedGraphics bg;
        //zoom
        private float iZoom = 1f;        //show Pic size
        private float showW;
        private float showH;        private float srcW;
        private float srcH;        //show Pic Left_Up point.
        private int showX, showY;        //Mouse Action Points:
        private int startX, startY, endX, endY;
        bool mouseDown = false;
        bool mouseMoved = false;        private Graphics MyGraphics;
        private int Hotkey_UP;
        private int Hotkey_DOWN;
        private int Hotkey_LEFT;
        private int Hotkey_RIGHT;
        private int Hotkey_ZoomIN; //suo xiao 
        private int Hotkey_ZoomOUT; //fang da
        private int Hotkey_NoZoom;
        private DirectoryInfo srcFolder;
        FileInfo curFile;        private int inputStatus;
        private int inputStep;
        private int inputType;        private MyFolderDAO mfolderDAO = new MyFolderDAO();
        private MyInputDAO minputDAO = new MyInputDAO();
        private MyUserInputDAO uiDAO = new MyUserInputDAO();        private int nextID;
        private InputInfo nextInput;
        private InputInfo input1;
        private bool finish = false;        #endregion
        public InputForm()
        {
            InitializeComponent();
            this.SetStyle(ControlStyles.OptimizedDoubleBuffer | ControlStyles.AllPaintingInWmPaint | ControlStyles.UserPaint, true);
            this.UpdateStyles();
        }        private void Form1_Load(object sender, EventArgs e)
        {
            try
            {                InitSrcFolder();
                InitSrcImage();
                this.Visible = true;
                InitImgAndGraph();
                gOfToDrawBeffor.DrawImage(srcImage, 0, 0);
                MyGraphics = panel1.CreateGraphics();
                ctx = BufferedGraphicsManager.Current;
                bg = ctx.Allocate(MyGraphics, new Rectangle(new Point(0, 0), panel1.Size));
                gOfbuff = bg.Graphics;            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
                Runtime.InputForm.Close();
            }
        }
      
        #region Paint              private void ZoomInOutPic()
        {
            if (srcImage != null)
            {
                InitImgAndGraph();                this.showW = srcImage.Width * iZoom;
                this.showH = srcImage.Height * iZoom;
                gOfToDrawBeffor.DrawImage(srcImage, 0, 0, this.showW, this.showH);
                //let it dont be out of range;
                if (-showX > showW)
                {
                    showX = ((int)showW / 10) * (-10);
                }
                if (-showY > showH)
                {
                    showY = ((int)showH / 10) * (-10);
                }                gOfbuff.Clear(panel1.BackColor);
                gOfbuff.DrawImage(toDrawBeffor, showX, showY);                if (mouseDown)
                {
                    gOfbuff.DrawRectangle(Pens.Red, startX, startY, endX - startX, endY - startY);
                }
                bg.Render();
            }
        }
        private void panel1_Paint(object sender, PaintEventArgs e)
        {            if (gOfbuff != null)
            {
                ZoomInOutPic();
            }
        }        private void panel1_MouseMove(object sender, MouseEventArgs e)
        {
            if (mouseDown)
            {
                mouseMoved = true;                endX = e.X;
                endY = e.Y;
                ZoomInOutPic();            }
        }        private void panel1_MouseDown(object sender, MouseEventArgs e)
        {
            startX = e.X;
            startY = e.Y;
            endX = e.X;
            endY = e.Y;
            mouseDown = true;        }        private void panel1_MouseUp(object sender, MouseEventArgs e)
        {
            mouseDown = false;
            if (mouseMoved)
            {
                mouseMoved = false;                float i = 1;                if (iZoom < 2)
                {
                    i = 2 / iZoom;
                    iZoom = 2f;                }
                float pCenterX = panel1.Width / 2;
                float pCenterY = panel1.Height / 2;                float mouCenterX = (startX + endX) / 2;
                float mouCenterY = (startY + endY) / 2;
                float cmouX = (mouCenterX - showX) * i + showX;
                float cmouY = (mouCenterY - showY) * i + showY;
                showX = (int)(pCenterX + showX - cmouX);
                showY = (int)(pCenterY + showY - cmouY);                ZoomInOutPic();
            }        }        private void InitImgAndGraph()
        {            toDrawBeffor = new Bitmap((int)(srcW * iZoom), (int)(srcW * iZoom));            gOfToDrawBeffor = Graphics.FromImage(toDrawBeffor);
        }
        private void InputForm2_FormClosing(object sender, FormClosingEventArgs e)
        {
            if (!e.Cancel)
            {
                if (srcImage != null)
                {
                    srcImage.Dispose();
                    srcImage = null;
                }
                Runtime.Main.Show();
            }
        }        #endregion        #region Init        private void InitSrcImage()
        {
            if (srcImage != null)
            {
                srcImage.Dispose();
                srcImage = null;
            }
            curFile = new FileInfo(Path.Combine(srcFolder.FullName, minputDAO.getImageName(nextID)));
            srcImage = new Bitmap(curFile.FullName);
            srcW = srcImage.Width;
            srcH = srcImage.Height;
            showW = srcImage.Width;
            showH = srcImage.Height;
            showX = 0;
            showY = 0;
            iZoom = 1f;
        }
  }
}
参考一下

Answer 5

mousedown 里定义起点，mousemove里绘制线，mouseup里定义终点
重复绘制的过程中会保留以前绘制的图像，
如果想每次都绘制新的图像，需要在绘制的时候首先清楚上次绘制的图像。如果用panel的话，可以用pane.CreateGraphics（）.clear(color);color 为你图像的背景色，用于清除上次图像

Answer 6

angel 16709 谢谢你提供的代码，我研究一下。