问题
I am trying to build a WinForm application that will load an image file from an openfiledialog and load it into either a panel or picturebox. I want to be able to draw multiple rectangles with the left mouse button and have them stay on the image. I have been successful in getting a single rectangle at a time on the actual form but not on an image inside a panel/picturebox. Does anyone know of a resource that would help me understand how to achieve this?
This is the code that allows me to draw a single resizable rectangle on the form, but when I change the mouse events from form1_MouseEvent to panel1_MouseEvent it does nothing..
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;
namespace Temporary_Name_Utility
{
public partial class Form1 : Form
{
Rectangle myRectangle;
bool draw = false;
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
try
{
OpenFileDialog myFile = new OpenFileDialog();
myFile.Filter = "Image Files(*.img, *.bmp) |*.img; *.bmp;";
myFile.InitialDirectory = "c:\\";
if (myFile.ShowDialog() == DialogResult.OK)
{
pictureBox1.BackgroundImage = Image.FromFile(myFile.FileName);
}
}
catch (Exception error)
{
MessageBox.Show("Error loading the selected file. Original error: " + error.Message);
}
}
private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
{
myRectangle = new Rectangle(e.X, e.Y, 0, 0);
this.Invalidate();
}
private void pictureBox1_Paint(object sender, PaintEventArgs e)
{
if(draw)
{
using(Pen myPen = new Pen(Color.Red, 2))
{
e.Graphics.DrawRectangle(myPen, myRectangle);
}
}
}
private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
{
if(e.Button == MouseButtons.Left)
{
myRectangle = new Rectangle(myRectangle.Left, myRectangle.Top, Math.Min(e.X - myRectangle.Left, pictureBox1.ClientRectangle.Width - myRectangle.Left), Math.Min(e.Y - myRectangle.Top, pictureBox1.ClientRectangle.Height - myRectangle.Top));
}
this.Invalidate();
}
private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
{
}
}
}
回答1:
Finally got some working code: This allows the user to draw as many rectangles as wanted with the mouse inside of the picturebox.
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;
namespace Rectangle_Utility
{
public partial class Form1 : Form
{
Point startPos;
Point currentPos;
bool drawing;
List<Rectangle> myRectangles = new List<Rectangle>();
public Form1()
{
InitializeComponent();
this.DoubleBuffered = true;
}
#region Menu Tool Strip
private void selectFileToolStripMenuItem_Click(object sender, EventArgs e)
{
try
{
//Initiate new OpenFileDialog
//Filter for img and bmp files
//Start looking in root of c:
OpenFileDialog myFile = new OpenFileDialog();
myFile.Filter = "Image Files(*.img, *.bmp) |*.img; *.bmp;";
myFile.InitialDirectory = "c:\\";
//Set background image of pictureBox to file selected through OpenFileDialog
if (myFile.ShowDialog() == DialogResult.OK)
{
pictureBox1.BackgroundImage = Image.FromFile(myFile.FileName);
}
}
catch (Exception error)
{
MessageBox.Show("Error loading the selected file. Original error: " + error.Message);
}
}
private void exitToolStripMenuItem_Click(object sender, EventArgs e)
{
this.Close();
}
private void clearAllToolStripMenuItem_Click(object sender, EventArgs e)
{
}
private void zoomToolStripMenuItem_Click(object sender, EventArgs e)
{
}
private void undoLastActionToolStripMenuItem_Click(object sender, EventArgs e)
{
}
private void redoLastActionToolStripMenuItem_Click(object sender, EventArgs e)
{
}
#endregion
#region Rectangle
private Rectangle getRectangle()
{
return new Rectangle(
Math.Min(startPos.X, currentPos.X),
Math.Min(startPos.Y, currentPos.Y),
Math.Abs(startPos.X - currentPos.X),
Math.Abs(startPos.Y - currentPos.Y));
}
private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
{
if (e.Button == MouseButtons.Left)
{
currentPos = startPos = e.Location;
drawing = true;
}
}
private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
{
currentPos = e.Location;
if (drawing) pictureBox1.Invalidate();
}
private void pictureBox1_Paint(object sender, PaintEventArgs e)
{
if (myRectangles.Count > 0) e.Graphics.DrawRectangles(Pens.Black, myRectangles.ToArray());
if (drawing) e.Graphics.DrawRectangle(Pens.Red, getRectangle());
}
private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
{
if (drawing)
{
drawing = false;
var rect = getRectangle();
if (rect.Width > 0 && rect.Height > 0) myRectangles.Add(rect);
pictureBox1.Invalidate();
}
}
#endregion
}
}
回答2:
You have to create a graphic from image and use that graphic to draw the rectangle so that the rectangle will be drawn in the image.
Graphics newGraphics = Graphics.FromImage(image);
newGraphics.FillRectangle(new SolidBrush(Color.Black), rectangles);
来源：https://stackoverflow.com/questions/24084672/how-to-draw-multiple-rectangles-with-mouse-on-an-image