如果 src 使用 java 函数，如何获取验证码图像？

Question

如何从 this website 抓取验证码验证码图片。

我试过 MSHTML，但该网站使用 java 脚本函数在其 src 中显示检索验证码。请尝试回答我如何实现这一点。

Imports MahApps.Metro.Controls
Imports System.Net
Imports System.Windows.Forms


Class MainWindow
    Inherits MetroWindow

    Private Sub MetroWindow_Loaded(sender As Object, e As RoutedEventArgs)
        wb.Navigate("https://www.irctc.co.in/eticketing/loginHome.jsf")
        AddHandler wb.LoadCompleted, AddressOf wb_Loaded
    End Sub
    Private Sub btngo_Click(sender As Object, e As RoutedEventArgs) Handles btngo.Click
        Dim htmldoc As MSHTML.IHTMLDocument2 = wb.Document
        Dim usrtxtdoc As MSHTML.IHTMLElement = htmldoc.all.item("j_username", 0)
        Dim usrpwddoc As MSHTML.IHTMLElement = htmldoc.all.item("j_password", 0)
        Dim captchadoc As MSHTML.IHTMLElement = htmldoc.all.item("j_captcha", 0)
        usrtxtdoc.innerText = txtusrname.Text
        usrpwddoc.innerText = txtpwd.Text
        captchadoc.innerText = txtcaptcha.Text
    End Sub

    Private Sub wb_Loaded(sender As Object, e As System.Windows.Navigation.NavigationEventArgs)
        MsgBox("Loaded")
        Dim htmldoc As MSHTML.IHTMLDocument2 = wb.Document
        Dim htmldoc2 As MSHTML.HTMLDocument = wb.Document
        Dim captchaimg As MSHTML.HTMLImg = htmldoc.all.item("cimage", 0)
        Dim bitmap As New BitmapImage
        bitmap.BeginInit()
        bitmap.UriSource = New Uri(wb.FindResource("captchaImage"))
        bitmap.EndInit()
        imgcaptcha.Source = bitmap
    End Sub

    Private Sub wb_Navigated(sender As Object, e As NavigationEventArgs) Handles wb.Navigated
        lblwbstatus.Content = "Load Completed"
    End Sub

    Private Sub wb_Navigating(sender As Object, e As NavigatingCancelEventArgs) Handles wb.Navigating
        lblwbstatus.Content = "Navigating Please wait"
    End Sub

    Private Sub lblwbstatus_MouseDoubleClick(sender As Object, e As MouseButtonEventArgs) Handles lblwbstatus.MouseDoubleClick
        wb.Refresh()
    End Sub
End Class

您可以从 this link

下载源代码

Answer 1

通常你会这样做：

    Dim htmldoc As mshtml.IHTMLDocument2 = wb.Document.DomDocument
    Dim captchaimg As mshtml.HTMLImg = htmldoc.all.item("cimage", 0)
    Dim imgRange As IHTMLControlRange = htmldoc.body.createControlRange()
    For Each img As IHTMLImgElement In htmldoc.images
        If img.nameProp = "captchaImage" Then
            imgRange.add(img)
            imgRange.execCommand("Copy", False, Nothing)
            Using bmp As Bitmap = Clipboard.GetDataObject().GetData(DataFormats.Bitmap)
                bmp.Save("c:\test.bmp")
            End Using
        End If
    Next

但是，由于 Internet Explorer 问题，该图像有一个 alpha 通道未被复制到剪贴板（您可以在此处阅读 Copying image from page results in black image）。

其他方法是检查 Internet Explorer 缓存，但由于 HTTP headers，该图像不会被缓存，所以你运气不好。

Answer 2

考虑到以下方面，上面的代码工作得很好： 1- 项目类型- 如您的网页目标示例 ("IMG") 所示。 2- 图片专有名称示例：CaptchaImg.jpg 写成CaptchaImg.jpg 3- 添加对 (mshtml) 的引用并将 mshtml 导入您的项目 4- 右键单击项目上的引用 --> 单击添加引用 --> -->浏览按钮点击-选择或导航到---> C:\Windows\assembly\GAC\Microsoft.mshtml.0.3300.0__b03f5f7f11d50a3a\Microsoft.mshtml.dll ----> 确定按钮单击 --- 这会将 Microsoft.mshtml.dll 添加到您的参考最后将导入到您的项目中（导入 mshtml）。 5- 更改目录 bmp.Save("c:\test.bmp")---> 例如 bmp.Save("c:\test\test.bmp") 为安全和管理权限特权。

如果 src 使用 java 函数，如何获取验证码图像？

how to get captcha image if src use java function?

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