1Imports System
  2Imports System.Drawing
  3Imports System.Drawing.Drawing2D
  4Imports System.Drawing.Imaging
  5
  6/**/''' <summary>
  7''' CAPTCHA image generation class
  8''' </summary>
  9''' <remarks>
 10''' Adapted from the excellent code at 
 11''' http://www.codeproject.com/aspnet/CaptchaImage.asp
 12''' 该源码下载自www.51aspx.com(５1ａｓｐｘ．ｃｏｍ)
 13''' Jeff Atwood
 14''' http://www.codinghorror.com/
 15''' </remarks>
 16Public Class CaptchaImageClass CaptchaImage
 17
 18    Private _height As Integer
 19    Private _width As Integer
 20    Private _rand As Random
 21    Private _generatedAt As DateTime
 22    Private _randomText As String
 23    Private _randomTextLength As Integer
 24    Private _randomTextChars As String
 25    Private _fontFamilyName As String
 26    Private _fontWarp As FontWarpFactor
 27    Private _backgroundNoise As BackgroundNoiseLevel
 28    Private _lineNoise As LineNoiseLevel
 29    Private _guid As String
 30    Private _fontWhitelist As String
 31
 32Public Enums#Region "  Public Enums"
 33
 34    /**/''' <summary>
 35    ''' Amount of random font warping to apply to rendered text
 36    ''' </summary>
 37    Public Enum FontWarpFactorEnum FontWarpFactor
 38        None
 39        Low
 40        Medium
 41        High
 42        Extreme
 43    End Enum
 44
 45    /**/''' <summary>
 46    ''' Amount of background noise to add to rendered image
 47    ''' </summary>
 48    Public Enum BackgroundNoiseLevelEnum BackgroundNoiseLevel
 49        None
 50        Low
 51        Medium
 52        High
 53        Extreme
 54    End Enum
 55
 56    /**/''' <summary>
 57    ''' Amount of curved line noise to add to rendered image
 58    ''' </summary>
 59    Public Enum LineNoiseLevelEnum LineNoiseLevel
 60        None
 61        Low
 62        Medium
 63        High
 64        Extreme
 65    End Enum
 66
 67#End Region
 68
 69Public Properties#Region "  Public Properties"
 70
 71    /**/''' <summary>
 72    ''' Returns a GUID that uniquely identifies this Captcha
 73    ''' </summary>
 74    Public ReadOnly Property UniqueId()Property UniqueId() As String
 75        Get
 76            Return _guid
 77        End Get
 78    End Property
 79
 80    /**/''' <summary>
 81    ''' Returns the date and time this image was last rendered
 82    ''' </summary>
 83    Public ReadOnly Property RenderedAt()Property RenderedAt() As DateTime
 84        Get
 85            Return _generatedAt
 86        End Get
 87    End Property
 88
 89    /**/''' <summary>
 90    ''' Font family to use when drawing the Captcha text. If no font is provided, a random font will be chosen from the font whitelist for each character.
 91    ''' </summary>
 92    Public Property Font()Property Font() As String
 93        Get
 94            Return _fontFamilyName
 95        End Get
 96        Set(ByVal Value As String)
 97            Try
 98                Dim font1 As Font = New Font(Value, 12.0!)
 99                _fontFamilyName = Value
100                font1.Dispose()
101            Catch ex As Exception
102                _fontFamilyName = Drawing.FontFamily.GenericSerif.Name
103            End Try
104        End Set
105    End Property
106
107    /**/''' <summary>
108    ''' Amount of random warping to apply to the Captcha text.
109    ''' </summary>
110    Public Property FontWarp()Property FontWarp() As FontWarpFactor
111        Get
112            Return _fontWarp
113        End Get
114        Set(ByVal Value As FontWarpFactor)
115            _fontWarp = Value
116        End Set
117    End Property
118
119    /**/''' <summary>
120    ''' Amount of background noise to apply to the Captcha image.
121    ''' </summary>
122    Public Property BackgroundNoise()Property BackgroundNoise() As BackgroundNoiseLevel
123        Get
124            Return _backgroundNoise
125        End Get
126        Set(ByVal Value As BackgroundNoiseLevel)
127            _backgroundNoise = Value
128        End Set
129    End Property
130
131    Public Property LineNoise()Property LineNoise() As LineNoiseLevel
132        Get
133            Return _lineNoise
134        End Get
135        Set(ByVal value As LineNoiseLevel)
136            _lineNoise = value
137        End Set
138    End Property
139
140    /**/''' <summary>
141    ''' A string of valid characters to use in the Captcha text. 
142    ''' A random character will be selected from this string for each character.
143    ''' </summary>
144    Public Property TextChars()Property TextChars() As String
145        Get
146            Return _randomTextChars
147        End Get
148        Set(ByVal Value As String)
149            _randomTextChars = Value
150            _randomText = GenerateRandomText()
151        End Set
152    End Property
153
154    /**/''' <summary>
155    ''' Number of characters to use in the Captcha text. 
156    ''' </summary>
157    Public Property TextLength()Property TextLength() As Integer
158        Get
159            Return _randomTextLength
160        End Get
161        Set(ByVal Value As Integer)
162            _randomTextLength = Value
163            _randomText = GenerateRandomText()
164        End Set
165    End Property
166
167    /**/''' <summary>
168    ''' Returns the randomly generated Captcha text.
169    ''' </summary>
170    Public ReadOnly Property [()Property [Text]() As String
171        Get
172            Return _randomText
173        End Get
174    End Property
175
176    /**/''' <summary>
177    ''' Width of Captcha image to generate, in pixels 
178    ''' </summary>
179    Public Property Width()Property Width() As Integer
180        Get
181            Return _width
182        End Get
183        Set(ByVal Value As Integer)
184            If (Value <= 60) Then
185                Throw New ArgumentOutOfRangeException("width", Value, "width must be greater than 60.")
186            End If
187            _width = Value
188        End Set
189    End Property
190
191    /**/''' <summary>
192    ''' Height of Captcha image to generate, in pixels 
193    ''' </summary>
194    Public Property Height()Property Height() As Integer
195        Get
196            Return _height
197        End Get
198        Set(ByVal Value As Integer)
199            If Value <= 30 Then
200                Throw New ArgumentOutOfRangeException("height", Value, "height must be greater than 30.")
201            End If
202            _height = Value
203        End Set
204    End Property
205
206    /**/''' <summary>
207    ''' A semicolon-delimited list of valid fonts to use when no font is provided.
208    ''' </summary>
209    Public Property FontWhitelist()Property FontWhitelist() As String
210        Get
211            Return _fontWhitelist
212        End Get
213        Set(ByVal value As String)
214            _fontWhitelist = value
215        End Set
216    End Property
217
218#End Region
219
220    Public Sub New()Sub New()
221        _rand = New Random
222        _fontWarp = FontWarpFactor.Low
223        _backgroundNoise = BackgroundNoiseLevel.Low
224        _lineNoise = LineNoiseLevel.None
225        _width = 180
226        _height = 50
227        _randomTextLength = 5
228        _randomTextChars = "ACDEFGHJKLNPQRTUVXYZ2346789"
229        _fontFamilyName = ""
230        ' -- a list of known good fonts in on both Windows XP and Windows Server 2003
231        _fontWhitelist = _
232            "arial;arial black;comic sans ms;courier new;estrangelo edessa;franklin gothic medium;" & _
233            "georgia;lucida console;lucida sans unicode;mangal;microsoft sans serif;palatino linotype;" & _
234            "sylfaen;tahoma;times new roman;trebuchet ms;verdana"
235        _randomText = GenerateRandomText()
236        _generatedAt = DateTime.Now
237        _guid = Guid.NewGuid.ToString()
238    End Sub
239
240    /**/''' <summary>
241    ''' Forces a new Captcha image to be generated using current property value settings.
242    ''' </summary>
243    Public Function RenderImage()Function RenderImage() As Bitmap
244        Return GenerateImagePrivate()
245    End Function
246
247    /**/''' <summary>
248    ''' Returns a random font family from the font whitelist
249    ''' </summary>
250    Private Function RandomFontFamily()Function RandomFontFamily() As String
251        Static ff() As String
252        '-- small optimization so we don't have to split for each char
253        If ff Is Nothing Then
254            ff = _fontWhitelist.Split(";"c)
255        End If
256        Return ff(_rand.Next(0, ff.Length))
257    End Function
258
259    /**/''' <summary>
260    ''' generate random text for the CAPTCHA
261    ''' </summary>
262    Private Function GenerateRandomText()Function GenerateRandomText() As String
263        Dim sb As New System.Text.StringBuilder(_randomTextLength)
264        Dim maxLength As Integer = _randomTextChars.Length
265        For n As Integer = 0 To _randomTextLength - 1
266            sb.Append(_randomTextChars.Substring(_rand.Next(maxLength), 1))
267        Next
268        Return sb.ToString
269    End Function
270
271    /**/''' <summary>
272    ''' Returns a random point within the specified x and y ranges
273    ''' </summary>
274    Private Function RandomPoint()Function RandomPoint(ByVal xmin As Integer, ByVal xmax As Integer, ByRef ymin As Integer, ByRef ymax As Integer) As PointF
275        Return New PointF(_rand.Next(xmin, xmax), _rand.Next(ymin, ymax))
276    End Function
277
278    /**/''' <summary>
279    ''' Returns a random point within the specified rectangle
280    ''' </summary>
281    Private Function RandomPoint()Function RandomPoint(ByVal rect As Rectangle) As PointF
282        Return RandomPoint(rect.Left, rect.Width, rect.Top, rect.Bottom)
283    End Function
284
285