项目模板:要实现在背景和无背景上完成画线，画直线、矩形、椭圆、并能随意调整字体的大小
首先要定义绘制的类型
enum DrawMode
{
None, // 没有选择绘制型
Pen, // 画笔 画直线
Line,// 画直线
Rectangle,// 画矩形
Ellipse, // 画椭圆
Rubber // 橡皮擦
}//如果要想绘制成图片可以使用picturebox作为载体，
//之前使用g.drawLine只是绘制到窗体，只是表面现象，并没有绘制成图片
//把绘制的效果形成一个图片使用drawImage方法
全局变量：
Graphics g; //绘制对象
Graphics imgGra;// 把绘制出效果形成一个图片
Color curColor = Color.Black;//设置画笔的颜色
int penSize = 0;// 笔刷粗细
string title; // 窗体的标题
DrawMode curMode = DrawMode.None;//当前绘制的类型
Image backImg;// 背景图片设置下拉选项
g = this.CreateGraphics();
g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
toolStripComboBox1.SelectedIndex = 1; //设置下拉框默认值选择
this.Text = "画板";选择背景
private void 选择文件ToolStripMenuItem_Click(object sender, EventArgs e)
{
OpenFileDialog ofd = new OpenFileDialog();// 文本选择对话框
ofd.Filter = "png图片|*.png|jpg图片|*.jpg"; //过滤文件类型
ofd.Multiselect = false;//是否支持多选，
if (ofd.ShowDialog() == DialogResult.OK)
{
Image sourceImage = Image.FromFile(ofd.FileName);// 加载对应路径的资源 把图片绘制的背景
//this.ClientRectangle.Width窗体的宽度
//this.ClientRectangle.Height窗体的高度
backImg = new Bitmap(this.ClientRectangle.Width, this.ClientRectangle.Height);//设置背景图片大小
imgGra = Graphics.FromImage(backImg);// 把backImage作为绘制背景图
// 把图片绘制到管理背景图的图像上imgGra
//imgGra.DrawImage()
g.Clear(Color.White); //把绘制区域以白色填充，目的先把之前的背景清空掉
g.DrawImage(sourceImage, this.ClientRectangle);// 绘制图片，参数1是绘制的图片 参数2是绘制的区域
this.Text = title + "\t" + ofd.FileName;
}
}无背景
private void 无背景ToolStripMenuItem_Click(object sender, EventArgs e)
{
// 设置无背景的背景图宽度和高度
backImg = new Bitmap(this.ClientRectangle.Width, this.ClientRectangle.Height); //设置一张图片
imgGra = Graphics.FromImage(backImg);// 把图片作为绘制的背景
imgGra.Clear(Color.White); // 清空背景
g.DrawImage(backImg, this.ClientRectangle);//绘制图片
this.Text = title + "\t" + "未命名";
}点击画笔pen的事件
private void toolStripLabel2_Click(object sender, EventArgs e)
{
//只是修改绘制的类型，真正绘制的时候在鼠标移动方法进行绘制
curMode = DrawMode.Pen;
}鼠标按下事件
Point startPoint; // 起始点位置
bool drawFlag;// 控制是否开始绘制的变量
private void Form1_MouseDown(object sender, MouseEventArgs e)
{
if(e.Button == MouseButtons.Left)
{
startPoint = e.Location;// 把点击点坐标赋值给起始点
drawFlag = true;
}
}鼠标移动
private void Form1_MouseMove(object sender, MouseEventArgs e)
{
if (drawFlag == false) return;
switch (curMode) {
case DrawMode.None:
break;
case DrawMode.Pen:
// 粗细不要写定值 先写2
g.DrawLine(new Pen(curColor, penSize), startPoint, e.Location);
imgGra.DrawLine(new Pen(curColor, penSize), startPoint, e.Location);
startPoint = e.Location;
break;
case DrawMode.Line:
// 为了解决窗体最小化的时候出现 绘制的效果的消失的问题，
//打开窗体重新调用绘制的方法，把backimage重新绘制到窗体上
// 给窗体添加一个paint事件 把backimage重新绘制到窗体上
Form1_Paint(null, null);
g.DrawLine(new Pen(curColor, penSize), startPoint, e.Location);
break;
case DrawMode.Rectangle:
Form1_Paint(null, null);
g.DrawRectangle(new Pen(curColor, penSize), startPoint.X, startPoint.Y, e.Location.X - startPoint.X, e.Location.Y - startPoint.Y);
break;
case DrawMode.Ellipse:
Form1_Paint(null, null);
g.DrawEllipse(new Pen(curColor, penSize), startPoint.X, startPoint.Y, e.Location.X - startPoint.X, e.Location.Y - startPoint.Y);
break;
case DrawMode.Rubber:
// 绘制一个白色的线就行
g.DrawLine(new Pen(Color.White, 10), startPoint, e.Location);
imgGra.DrawLine(new Pen(Color.White, 10), startPoint, e.Location);
startPoint = e.Location;
break;
default:
break;
}
}鼠标松开
private void Form1_MouseUp(object sender, MouseEventArgs e)
{
drawFlag = false;
switch (curMode)
{
case DrawMode.None:
break;
case DrawMode.Pen:
break;
case DrawMode.Line:
imgGra.DrawLine(new Pen(curColor, penSize), startPoint, e.Location);
break;
case DrawMode.Rectangle:
imgGra.DrawRectangle(new Pen(curColor, penSize), startPoint.X, startPoint.Y, e.Location.X - startPoint.X, e.Location.Y - startPoint.Y);
break;
case DrawMode.Ellipse:
imgGra.DrawEllipse(new Pen(curColor, penSize), startPoint.X, startPoint.Y, e.Location.X - startPoint.X, e.Location.Y - startPoint.Y);
break;
case DrawMode.Rubber:
break;
default:
break;
}
}修改笔刷的颜色
private void 颜色ToolStripMenuItem_Click(object sender, EventArgs e)
{
//FontDialog
ColorDialog cd = new ColorDialog();
if (cd.ShowDialog() == DialogResult.OK)
{
curColor = cd.Color; //修改画笔颜色变量
}
}修改笔刷大小的事件
private void toolStripComboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
penSize = Convert.ToInt16( toolStripComboBox1.Text);
}修改绘制类型
private void toolStripLabel3_Click(object sender, EventArgs e)
{
curMode = DrawMode.Line; //绘制直线
}矩形
private void toolStripLabel4_Click(object sender, EventArgs e)
{
//矩形
curMode = DrawMode.Rectangle;
}椭圆
private void toolStripLabel5_Click(object sender, EventArgs e)
{
curMode = DrawMode.Ellipse;//椭圆
}在改事件中重新绘制图片
private void Form1_Paint(object sender, PaintEventArgs e)
{
if (backImg == null)
{
return;
}
g.DrawImage(backImg, this.ClientRectangle);
}private void toolStripLabel6_Click(object sender, EventArgs e)
{
curMode = DrawMode.Rubber;//
}
