Captchanın kullanıldığı yerler;
bot engellemeyi amaclar.
Art arda mesaj ve ya konu acmak isteyen kullanıcıyı kontrol amacıyla kullanılmaktadır.
Program Captcha yenile butonuna basıldığı zaman surekli değiştirir.
kontrol butonuna basıldığı zaman doğru girildiyse msgbox doğru girilmiştir yazar.
isteyen bundan esinlenerek form1 kısmına bunu koyabilir.
doğru girilirse form2 ye yonlendirir.
Kod:
Imports System.Drawing.Drawing2D Imports System.Math 'visualbasicdersleri.com Public Class Form1 #Region "CAPTCHA CİZ" Public Function CaptchaCiz(ByVal Metin As String, ByVal Genislik As Integer, ByVal Yukseklik As Integer, ByVal FontAilesi As String, ByVal ArkaStil As HatchStyle, ByVal YaziStil As HatchStyle, ByVal Onrenk As Color, ByVal ArkaRenk As Color) As Bitmap Dim bm As New Bitmap(Genislik, Yukseklik) Dim gr As Graphics = Graphics.FromImage(bm) gr.SmoothingMode = Drawing2D.SmoothingMode.HighQuality Dim rectf As New RectangleF(0, 0, Genislik, Yukseklik) Dim br As Brush 'visualbasicdersleri.com br = New HatchBrush(ArkaStil, Color.LightGray, Color.White) gr.FillRectangle(br, rectf) Dim text_size As SizeF Dim the_font As Font Dim font_size As Single = Yukseklik + 1 Do font_size -= 1 the_font = New Font(FontAilesi, font_size, FontStyle.Bold, GraphicsUnit.Pixel) text_size = gr.MeasureString(Metin, the_font) Loop While (text_size.Width > Genislik) OrElse (text_size.Height > Yukseklik) Dim string_format As New StringFormat string_format.Alignment = StringAlignment.Center string_format.LineAlignment = StringAlignment.Center Dim graphics_path As New GraphicsPath graphics_path.AddString(Metin, the_font.FontFamily, CInt(Font.Style), the_font.Size, rectf, string_format) Dim rnd As New Random Dim pts() As PointF = Dim mat As New Matrix graphics_path.Warp(pts, rectf, mat, WarpMode.Perspective, 0) br = New HatchBrush(HatchStyle.LargeConfetti, Color.Black, Color.DarkGray) gr.FillPath(br, graphics_path) Dim max_dimension As Integer = Max(Genislik, Yukseklik) For i As Integer = 0 To CInt(Genislik * Yukseklik / 30) Dim X As Integer = rnd.Next(Genislik) Dim Y As Integer = rnd.Next(Yukseklik) Dim W As Integer = CInt(rnd.Next(max_dimension) / 50) Dim H As Integer = CInt(rnd.Next(max_dimension) / 50) gr.FillEllipse(br, X, Y, W, H) Next i For i As Integer = 1 To 5 Dim x1 As Integer = rnd.Next(Genislik) Dim y1 As Integer = rnd.Next(Yukseklik) Dim x2 As Integer = rnd.Next(Genislik) Dim y2 As Integer = rnd.Next(Yukseklik) gr.DrawLine(Pens.DarkGray, x1, y1, x2, y2) Next i For i As Integer = 1 To 5 Dim x1 As Integer = rnd.Next(Genislik) Dim y1 As Integer = rnd.Next(Yukseklik) Dim x2 As Integer = rnd.Next(Genislik) Dim y2 As Integer = rnd.Next(Yukseklik) gr.DrawLine(Pens.LightGray, x1, y1, x2, y2) Next i graphics_path.Dispose() br.Dispose() 'visualbasicdersleri.com the_font.Dispose() gr.Dispose() Return bm End Function #End Region Dim chars = "ABCDEFGHIJKLMNOPQRSTyvwxyzabcdefghijklmnopqrstyvw xyz123456789" Function RastgeleMetin(ByVal Uzunluk As Integer) Dim r, i Dim x As String 'visualbasicdersleri.com For i = 0 To Uzunluk Randomize() r = Int((Rnd() * 61) + 1) x = x & Mid(chars, r, 1) Next i Return x End Function Dim ActCaptcha As String ' Captchayı programda tutacak değişken belirleniyor. Private Sub Form1_Load() Handles MyBase.Load Ciz() End Sub Sub Ciz() ActCaptcha = RastgeleMetin(5) Dim Captcha As Bitmap = CaptchaCiz(ActCaptcha, PictureBox1.ClientSize.Width, PictureBox1.ClientSize.Height, Me.Font.FontFamily.Name, HatchStyle.SmallConfetti, HatchStyle.Cross, Color.LightGray, Color.White) PictureBox1.Image = Captcha 'visualbasicdersleri.com End Sub Private Sub Button1_Click() Handles Button1.Click Ciz() End Sub Private Sub Button2_Click() Handles Button2.Click If TextBox1.Text = ActCaptcha Then MsgBox("Doğru girdiniz.", MsgBoxStyle.Information, "Doğru") Else MsgBox("Yanlış girdiniz.", MsgBoxStyle.Critical, "Yanlış") Ciz() End If End Sub End Class
kaynak visualbasicdersleri.com
bot engellemeyi amaclar.
Art arda mesaj ve ya konu acmak isteyen kullanıcıyı kontrol amacıyla kullanılmaktadır.
Program Captcha yenile butonuna basıldığı zaman surekli değiştirir.
kontrol butonuna basıldığı zaman doğru girildiyse msgbox doğru girilmiştir yazar.
isteyen bundan esinlenerek form1 kısmına bunu koyabilir.
doğru girilirse form2 ye yonlendirir.
Kod:
Imports System.Drawing.Drawing2D Imports System.Math 'visualbasicdersleri.com Public Class Form1 #Region "CAPTCHA CİZ" Public Function CaptchaCiz(ByVal Metin As String, ByVal Genislik As Integer, ByVal Yukseklik As Integer, ByVal FontAilesi As String, ByVal ArkaStil As HatchStyle, ByVal YaziStil As HatchStyle, ByVal Onrenk As Color, ByVal ArkaRenk As Color) As Bitmap Dim bm As New Bitmap(Genislik, Yukseklik) Dim gr As Graphics = Graphics.FromImage(bm) gr.SmoothingMode = Drawing2D.SmoothingMode.HighQuality Dim rectf As New RectangleF(0, 0, Genislik, Yukseklik) Dim br As Brush 'visualbasicdersleri.com br = New HatchBrush(ArkaStil, Color.LightGray, Color.White) gr.FillRectangle(br, rectf) Dim text_size As SizeF Dim the_font As Font Dim font_size As Single = Yukseklik + 1 Do font_size -= 1 the_font = New Font(FontAilesi, font_size, FontStyle.Bold, GraphicsUnit.Pixel) text_size = gr.MeasureString(Metin, the_font) Loop While (text_size.Width > Genislik) OrElse (text_size.Height > Yukseklik) Dim string_format As New StringFormat string_format.Alignment = StringAlignment.Center string_format.LineAlignment = StringAlignment.Center Dim graphics_path As New GraphicsPath graphics_path.AddString(Metin, the_font.FontFamily, CInt(Font.Style), the_font.Size, rectf, string_format) Dim rnd As New Random Dim pts() As PointF = Dim mat As New Matrix graphics_path.Warp(pts, rectf, mat, WarpMode.Perspective, 0) br = New HatchBrush(HatchStyle.LargeConfetti, Color.Black, Color.DarkGray) gr.FillPath(br, graphics_path) Dim max_dimension As Integer = Max(Genislik, Yukseklik) For i As Integer = 0 To CInt(Genislik * Yukseklik / 30) Dim X As Integer = rnd.Next(Genislik) Dim Y As Integer = rnd.Next(Yukseklik) Dim W As Integer = CInt(rnd.Next(max_dimension) / 50) Dim H As Integer = CInt(rnd.Next(max_dimension) / 50) gr.FillEllipse(br, X, Y, W, H) Next i For i As Integer = 1 To 5 Dim x1 As Integer = rnd.Next(Genislik) Dim y1 As Integer = rnd.Next(Yukseklik) Dim x2 As Integer = rnd.Next(Genislik) Dim y2 As Integer = rnd.Next(Yukseklik) gr.DrawLine(Pens.DarkGray, x1, y1, x2, y2) Next i For i As Integer = 1 To 5 Dim x1 As Integer = rnd.Next(Genislik) Dim y1 As Integer = rnd.Next(Yukseklik) Dim x2 As Integer = rnd.Next(Genislik) Dim y2 As Integer = rnd.Next(Yukseklik) gr.DrawLine(Pens.LightGray, x1, y1, x2, y2) Next i graphics_path.Dispose() br.Dispose() 'visualbasicdersleri.com the_font.Dispose() gr.Dispose() Return bm End Function #End Region Dim chars = "ABCDEFGHIJKLMNOPQRSTyvwxyzabcdefghijklmnopqrstyvw xyz123456789" Function RastgeleMetin(ByVal Uzunluk As Integer) Dim r, i Dim x As String 'visualbasicdersleri.com For i = 0 To Uzunluk Randomize() r = Int((Rnd() * 61) + 1) x = x & Mid(chars, r, 1) Next i Return x End Function Dim ActCaptcha As String ' Captchayı programda tutacak değişken belirleniyor. Private Sub Form1_Load() Handles MyBase.Load Ciz() End Sub Sub Ciz() ActCaptcha = RastgeleMetin(5) Dim Captcha As Bitmap = CaptchaCiz(ActCaptcha, PictureBox1.ClientSize.Width, PictureBox1.ClientSize.Height, Me.Font.FontFamily.Name, HatchStyle.SmallConfetti, HatchStyle.Cross, Color.LightGray, Color.White) PictureBox1.Image = Captcha 'visualbasicdersleri.com End Sub Private Sub Button1_Click() Handles Button1.Click Ciz() End Sub Private Sub Button2_Click() Handles Button2.Click If TextBox1.Text = ActCaptcha Then MsgBox("Doğru girdiniz.", MsgBoxStyle.Information, "Doğru") Else MsgBox("Yanlış girdiniz.", MsgBoxStyle.Critical, "Yanlış") Ciz() End If End Sub End Class
kaynak visualbasicdersleri.com
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