实现过程:

(1) 新建窗体应用程序

(2) 添加一个MenuScrip控件;添加一个ToolScrip控件。

在ToolScrip控件中对每个单元,要将DisplayStyle属性改为Text

C#简单画图程序-LMLPHP

(3)程序代码。

1、新建菜单事件主要用白色清除窗体的背景,从而实现“文件新建”功能

[csharp] view plain copy
private void 新建ToolStripMenuItem_Click(object sender, EventArgs e)
{
Graphics g = this.CreateGraphics();
g.Clear(backColor);
toolStrip1.Enabled = true;
//创建一个Bitmap
theImage = new Bitmap(this.ClientRectangle.Width, this.ClientRectangle.Height);
editFileName = "新建文件";
//修改窗口标题
this.Text = "MyDraw\t" + editFileName;
ig = Graphics.FromImage(theImage);
ig.Clear(backColor);
}

  2、打开事件用于打开“打开文件”对话框,并选择相应的图片,将图片绘制到窗体上.

[csharp] view plain copy
private void 打开ToolStripMenuItem_Click(object sender, EventArgs e)
{
openFileDialog1.Multiselect = false;
if (openFileDialog1.ShowDialog() == DialogResult.OK)
{
//修改窗口标题
this.Text = "MyDraw\t" + openFileDialog1.FileName;
editFileName = openFileDialog1.FileName;
theImage = Image.FromFile(openFileDialog1.FileName);
Graphics g = this.CreateGraphics();
g.DrawImage(theImage, this.ClientRectangle);
ig = Graphics.FromImage(theImage);
ig.DrawImage(theImage, this.ClientRectangle);
//ToolBar可以使用了
toolStrip1.Enabled = true;
}
}

  (3) 保存菜单项的Click事件用于将窗体背景保存为BMP格式的图片

[csharp] view plain copy
private void 保存ToolStripMenuItem_Click(object sender, EventArgs e)
{
saveFileDialog1.Filter = "图像(*.bmp)|*.bmp";
saveFileDialog1.FileName = editFileName;
if (saveFileDialog1.ShowDialog() == DialogResult.OK)
{
theImage.Save(saveFileDialog1.FileName, ImageFormat.Bmp);
this.Text = "MyDraw\t" + saveFileDialog1.FileName;
editFileName = saveFileDialog1.FileName;
}
}

  (4) 在Paint事件中将Image中保存的图像,绘制出来

[csharp] view plain copy
private void Form1_Paint(object sender, PaintEventArgs e)
{
//将Image中保存的图像,绘制出来
Graphics g = this.CreateGraphics();
if (theImage != null)
{
g.Clear(Color.White);
g.DrawImage(theImage, this.ClientRectangle);
}
}

  

(5)添加Frm_Text.cs文字输入框。

添加一个Window窗体,取名为Frm_Text,然后对窗体的属性修改:

把FormBorderStyle属性改为 None;

C#简单画图程序-LMLPHP

把Modifiers的属性改为 Public

(6) 在窗体的MouseDown事件中,如果当前绘制的是字符串,在鼠标的当前位置显示文本框;如果绘制的是图开,设置图形的起始位置。

[cpp] view plain copy
private void Frm_Main_MouseDown(object sender, MouseEventArgs e)
{
if (e.Button == MouseButtons.Left)
{
//如果选择文字输入,则打开strInput窗体
if (drawTool == drawTools.String)
{
Frm_Text inputBox = new Frm_Text();
inputBox.StartPosition = FormStartPosition.CenterParent;
if (inputBox.ShowDialog() == DialogResult.OK)
{
Graphics g = this.CreateGraphics();
Font theFont = this.Font;
g.DrawString(inputBox.textBox1.Text, theFont, new SolidBrush(foreColor), e.X, e.Y);
ig.DrawString(inputBox.textBox1.Text, theFont, new SolidBrush(foreColor), e.X, e.Y);
}
}
//如果开始绘制,则开始记录鼠标位置
else if ((isDrawing = !isDrawing) == true)
{
startPoint = new Point(e.X, e.Y);
oldPoint = new Point(e.X, e.Y);
}
}
}

  (7) 在窗体的MouseMove 事件中,根据鼠标移动的大小绘制指定的图形.

[cpp] view plain copy
private void Form1_MouseMove(object sender, MouseEventArgs e)
{
Graphics g;
g = this.CreateGraphics(); if (isDrawing)
{
switch (drawTool)
{
case drawTools.None:
break;
case drawTools.Pen:
//从上一个点到当前点绘制线段
g.DrawLine(new Pen(foreColor, 1), oldPoint, new Point(e.X, e.Y));
ig.DrawLine(new Pen(foreColor, 1), oldPoint, new Point(e.X, e.Y));
oldPoint.X = e.X;
oldPoint.Y = e.Y;
break;
case drawTools.Line:
//首先恢复此次操作之前的图像,然后再添加Line
this.Frm_Main_Paint(this, new PaintEventArgs(this.CreateGraphics(), this.ClientRectangle));
g.DrawLine(new Pen(foreColor, 1), startPoint, new Point(e.X, e.Y));
break;
case drawTools.Ellipse:
//首先恢复此次操作之前的图像,然后再添加Ellipse
this.Frm_Main_Paint(this, new PaintEventArgs(this.CreateGraphics(), this.ClientRectangle));
g.DrawEllipse(new Pen(foreColor, 1), startPoint.X, startPoint.Y, e.X - startPoint.X, e.Y - startPoint.Y);
break;
case drawTools.Rectangle:
//首先恢复此次操作之前的图像,然后再添加Rectangle
this.Frm_Main_Paint(this, new PaintEventArgs(this.CreateGraphics(), this.ClientRectangle));
g.DrawRectangle(new Pen(foreColor, 1), startPoint.X, startPoint.Y, e.X - startPoint.X, e.Y - startPoint.Y);
break;
case drawTools.String:
break;
case drawTools.Rubber:
//用背景色绘制宽线段
g.DrawLine(new Pen(backColor, 20), oldPoint, new Point(e.X, e.Y));
ig.DrawLine(new Pen(backColor, 20), oldPoint, new Point(e.X, e.Y));
oldPoint.X = e.X;
oldPoint.Y = e.Y;
break;
}
}
}

  (8) 在窗体的MouseUp事件中,根据用户选择的画笔,绘制直线,椭圆或矩形等指定图形。

[csharp] view plain copy
private void Form1_MouseUp(object sender, MouseEventArgs e)
{
isDrawing = false;
switch (drawTool)
{
case drawTools.Line:
ig.DrawLine(new Pen(foreColor, 1), startPoint, new Point(e.X, e.Y));
break;
case drawTools.Ellipse:
ig.DrawEllipse(new Pen(foreColor, 1), startPoint.X, startPoint.Y, e.X - startPoint.X, e.Y - startPoint.Y);
break;
case drawTools.Rectangle:
ig.DrawRectangle(new Pen(foreColor, 1), startPoint.X, startPoint.Y, e.X - startPoint.X, e.Y - startPoint.Y);
break;
}
}

  

=============================================================================================================

这里解释为什么在拉直线时线会跟着鼠标动,而用选择画笔时移动鼠标就会画出线。

这里有两个Graphics:

(1) 真实的场景graphics.   它它上面画出的画面就是我个看到的画面。

eg:

private void Form1_Paint(object sender, PaintEventArgs e)
             {
                     //将Image中保存的图像,绘制出来
                      Graphics g = this.CreateGraphics();

(2)做为临时存储用的Graphic.

它在新建的时候创建:

[csharp] view plain copy
//创建一个Bitmap
theImage = new Bitmap(this.ClientRectangle.Width, this.ClientRectangle.Height);
editFileName = "新建文件";
//修改窗口标题
this.Text = "MyDraw\t" + editFileName;
ig = Graphics.FromImage(theImage);
ig.Clear(backColor);

  显示出来: 把theImage显示出来就是把以前保存在ig里的东西显示出来了

[csharp] view plain copy
private void Frm_Main_Paint(object sender, PaintEventArgs e)
{
//将Image中保存的图像,绘制出来
Graphics g = this.CreateGraphics();
if (theImage != null)
{
g.Clear(Color.White);
g.DrawImage(theImage, this.ClientRectangle);
}
}

  

在Form1_MouseMove里

如果是画笔,那么把图像保存到了两个graphic中,这样我们可以看到移动的画,最后也将显示所有画。

如果直线或矩形,那么只先画到第一个graphics里,在鼠标放开时才画到第二个graphic里。

通过本实例了解如何在窗体上绘制各种图形,如矩形、椭圆、线条、文字等。运行效果如下:

C#简单画图程序-LMLPHP

04-16 11:38