BBS多变个性贴图的实现，用ASP.NET网页动态生成图片

作者：阿赖 （Email: A at Lai.com.cn 主页：http://www.9499.net Blog: http://blog.csdn.net/laily/ ）

关键字：Asp.NET贴图程序 VB.NET编程

摘要：使用ASP.NET动态生成用于BBS贴图的动态图片。即ASPX页面通过改变querrystring参数的输出不同图片的示例程序。

某日在论坛上看到别人发言用的是搞笑的图片，发言的文字就在图片中，看了一下图片的地址原来是动态生成的，可以通过改地址中的一些参数就可以生成另外的图片，显示不同的文字。如这个地址：

http://gzx.zcat.net/isay.ashx?fontsize=24&index=02&what=HelloWorld

将显示下面的图片：

现在你试着修改一下fontsize、index、what这些参数的值看看，这样的图片用在论坛中贴图挺用趣的吧:)

这个动态生成图片的程序是如何实现的呢？经过一番研究，我发现使用.NET提供的强大的绘图功能实现这样的程序真是小菜一碟(a piece of cake)。

STEP：

建个ASP.NET WEB项目，将一些模板的图片（如果你象我这样懒，不想自己做图片那就直接用上面的吧，what参数为空，index分别等于1,2……，生成的图片保存下来就行了）文件名为1.jpg，2.jpg，3.jpg……，存在template目录下。

建个WEB FORM，页面上不必添加任何东东，Page_onload事件中写如下代码就搞定了：

        Dim Size, Index, sColor, sFont, say As String
        Request.ContentEncoding = System.Text.Encoding.Unicode
        Size = Request.QueryString("Size")
        Index = Request.QueryString("index")
        sColor = Request.QueryString("color")
        sFont = Request.QueryString("font")
        say = Request.QueryString("say")
        Response.Clear()
        Response.ContentType = "image/jpeg"
        Response.Charset = "gb-2312"
        If say = "" Then
            Size = 8
            Index = 999
            say = "地址后加参数：?index=&say=&font=&color=&size="
            say &= "index:1-9  say:显示的文字 font:字体 color:颜色（如:red) size:文字大小"
        End If
        If Size = "" Or Not Microsoft.VisualBasic.IsNumeric(Size) Then Size = 12
        If Index = "" Then Index = "1"
        Dim oFont As Font
        Try
            ofont = New Font(sFont, Single.Parse(Size))
        Catch
            oFont = New Font(FontFamily.GenericSerif, 12)
        End Try
        Dim strFilePath As String = Server.MapPath("template" & Index & ".jpg")
        If Not IO.File.Exists(strFilePath) Then
            Index = "1"
            strFilePath = Server.MapPath("template" & Index & ".jpg")
        End If
        Dim oBmp As Bitmap
        If IO.File.Exists(strFilePath) Then
            oBmp = New Bitmap(strFilePath)
        Else
            oBmp = New Bitmap(200, 100, PixelFormat.Format24bppRgb)
        End If
        Dim fColor, defColor As Brush
        defColor = Brushes.Black
        Dim x As Single = 10
        Dim y As Single = 10
        Dim w As Single = 50
        Dim h As Single = 50
        Select Case Index
            Case "1"
                defColor = Brushes.White
                w = 280 : h = 70
            Case "2"
                defColor = Brushes.Red
                x = 0 : y = 0
                w = 175 : h = 80
            Case "3"
                defColor = Brushes.Blue
                x = 15 : y = 310
                w = 530 : h = 115
            Case "4"
                defColor = Brushes.Black
                x = 155 : y = 5
                w = 435 : h = 140
            Case "5"
                defColor = Brushes.Red
                x = 5 : y = 140
                w = 305 : h = 90
            Case "6"
                defColor = Brushes.Beige
                x = 155 : y = 5
                w = 435 : h = 140
            Case "7"
                defColor = Brushes.Gray
                x = 0 : y = 0
                w = 175 : h = 80
            Case "8"
                defColor = Brushes.Black
                x = 155 : y = 5
                w = 435 : h = 140
            Case "9"
                defColor = Brushes.DarkBlue
                x = 155 : y = 5
                w = 435 : h = 140
        End Select
        Select Case LCase(sColor)
            Case "white" : fColor = Brushes.White
            Case "black" : fColor = Brushes.Black
            Case "red" : fColor = Brushes.Red
            Case "yellow" : fColor = Brushes.Yellow
            Case "green" : fColor = Brushes.Green
            Case "gray" : fColor = Brushes.Gray
            Case "blue" : fColor = Brushes.Blue
            Case "brown" : fColor = Brushes.Brown
            Case "coral" : fColor = Brushes.Coral
            Case "darkblue" : fColor = Brushes.DarkBlue
            Case "gold" : fColor = Brushes.Gold
            Case "orange" : fColor = Brushes.Orange
            Case Else : fColor = defColor
        End Select

        Dim oGrap As Graphics = Graphics.FromImage(oBmp)
        oGrap.DrawString(say, oFont, fColor, New RectangleF(x, y, w, h), StringFormat.GenericTypographic)
        oBmp.Save(Response.OutputStream, ImageFormat.Jpeg)

        oGrap.Dispose()
        oBmp.Dispose()
        Response.End()

使用方法跟前面提到了差不多，增加了字体和颜色两个参数，用法是：

程序页面地址?index=&say=&font=&color=&size="

注意x,y,w,h是图片文字框的位置和大小，请根据相应的图片作相应的设置。其实更好的办法是，将这图片的相关参数放到Web.config中，将会使程序更灵活和方便布署。