对图像的处理操纵

一、图像格式的转换

string strFilePathName = ImageShow.ImageUrl;
            System.Drawing.Image i = System.Drawing.Image.FromFile(strFilePathName);
        
            //以下得到在服务器上保存的文件路径名称
            string strFileName = Path.GetFileNameWithoutExtension(strFilePathName);
            ImageFormat f = ImageFormat.Bmp;
            switch(ddlFormat.SelectedItem.Text.ToLower())//toLower为转换为小写
            {
                case "bmp":
                    break;
                case "jpeg":
                    f = ImageFormat.Jpeg;
                    break;
                case "gif":
                    f = ImageFormat.Gif;
                    break;
                case "png":
                    f = ImageFormat.Png;
                    break;
                case "tiff":
                    f = ImageFormat.Tiff;
                    break;
            }
            string strSeverPath=tbPath.Text+"\\"+strFileName+"."+
                ddlFormat.SelectedItem.Text;
            i.Save(strSeverPath,f);

下面是实现在图片上写字、切割图片、拉伸和旋转
 对图片的处理和显示最好放在不同的页面，负责回显示满的
比如写字，切割等按钮放在一个页面，对这些操作放在Session里面保存
 比如按钮执行  Session["Add"] = true;  Session["Path"] = InputFile.PostedFile.FileName是保存图片的路径，在改页面放一个图片控件比如：
<asp:Image id="Image1"  runat="server" Height="370px" Width="508px" ImageUrl="genpicture.aspx"></asp:Image>
genpicture.aspx这个是另一个页面，在这个页面来处理图像。
代码如下：

if(Session["Path"]!=null)
            {
//                Response.Clear();
//                Response.Write("<br>");
//                Response.Write("<br>");
                System.Drawing.Image g=System.Drawing.Image.FromFile(Session["Path"].ToString());
                System.Drawing.Imaging.ImageFormat f=g.RawFormat;
                Bitmap b=new Bitmap(g);
                if(Session["RotateFlip"]!=null)
                    b.RotateFlip(RotateFlipType.Rotate90FlipNone);//旋转图片

                Graphics gh=Graphics.FromImage(b);
                if(Session["Add"]!=null)
                    gh.DrawString("MSDN荣誉出品",new Font("宋体",50),Brushes.Red ,5,b.Height-100);//给图片上添加文字
                //             拉伸图片 
                if(Session["Exp"]!=null)
                {
                    gh.Clear(Color.White);
                    gh.DrawImage(g,new Rectangle(10,10,50,50),new Rectangle(0,0,g.Width,g.Height),GraphicsUnit.Pixel);//17
                }
                //"切割图片 
                if(Session["Cut"]!=null)
                {
                    gh.Clear(Color.White);
                    gh.DrawImage(g,50,100,new Rectangle(80,80,410,410),GraphicsUnit.Pixel); //19
                }
 
                gh.SmoothingMode=SmoothingMode.AntiAlias;
                b.Save(Response.OutputStream,f);                         
                gh.Dispose();
                b.Dispose();
                g.Dispose();
                Session["RotateFlip"]=null;
                Session["Cut"]=null;
                Session["Exp"]=null;
                Session["Exp"]=null;
                Session["Cut"]=null;

            }

下面是对图片的一些基本操作画图

Bitmap b = new Bitmap(600,600);
            Graphics g = Graphics.FromImage(b);//GDI+中最重要的类
            g.Clear(Color.Red);
            Pen p = new Pen(Color.Green,3.0f);//铅笔
            g.DrawLine(p,0,0,600,600);
            g.DrawLine(p,600,0,0,600);
            g.DrawEllipse(p,0,0,100,100);
            SolidBrush sb = new SolidBrush(Color.Blue);//固体刷
            g.FillEllipse(sb,100,100,200,200);
            g.FillRectangle(sb,300,300,100,100);
            Font f = new Font("宋体",40);//字体
            g.DrawString("哈哈，不错！",f,sb,0,300);
            Point[] arrP = new Point[5];//point为基本的点
            arrP[0] = new Point(200,200);
            arrP[1] = new Point(200,400);
            arrP[2] = new Point(500,400);
            arrP[3] = new Point(500,600);
            arrP[4] = new Point(300,600);
            g.DrawPolygon(p,arrP);
            b.Save(Response.OutputStream,ImageFormat.Gif);