问使用regex编辑包含文本和多个图像的html字符串

EN

Sub Main()
    Dim htmlstring As String = "<IMG src=""data:image/png;base64,iVBORw0KG....""> " & vbCrLf _
& "<img src=""data:image/png;base64,iVBORw0KG...."">" & vbCrLf _
& "<p>blahblah</p>" & vbCrLf _
& "<IMG src=""data:image/png;base64,iVBORw0KG...."">" & vbCrLf _
& "<p>blahblah</p>"

    ' find all indxes of img using regex and lambda exprations '
    Dim indexofIMG() As Integer = Regex.Matches(htmlstring, "IMG", RegexOptions.IgnoreCase) _
.Cast(Of Match)().Select(Function(x) x.Index).ToArray()

    ' check from each index of "IMG" if "/" is missing '
    For Each itm As Integer In indexofIMG
        Dim counter As Integer = itm
        While counter < htmlstring.Length - 1
            If htmlstring(counter) = ">" Then
                If htmlstring(counter - 1) <> "/" Then
                    ' fix the missing "/" using Insert() method '
                    htmlstring = htmlstring.Insert(counter, "/")
                End If
                Exit While
            End If
            counter += 1
        End While
    Next

    Console.WriteLine(htmlstring)
    Console.ReadLine()
End Sub

Imports System.IO
Imports iTextSharp.text
Imports iTextSharp.tool.xml
Imports iTextSharp.text.pdf
Imports iTextSharp.tool.xml.parser
Imports iTextSharp.tool.xml.pipeline.css
Imports iTextSharp.tool.xml.pipeline.html
Imports iTextSharp.tool.xml.pipeline.end
Imports iTextSharp.tool.xml.html
Imports System.Text.RegularExpressions

Public Class Form1

    Dim dsktop As String = My.Computer.FileSystem.SpecialDirectories.Desktop
    Public Function GetFormattedHTML(str As String) As String
        'format images by changing > to />
        ' find all indxes of img using regex and lambda exprations '
        Dim indexofIMG() As Integer = Regex.Matches(str.ToString, "IMG", RegexOptions.IgnoreCase) _
        .Cast(Of Match)().Select(Function(x) x.Index).ToArray()

        ' check from each index of "IMG" if "/" is missing '
        For Each itm As Integer In indexofIMG
            Dim counter As Integer = itm
            While counter < str.ToString.Length - 1
                If str(counter) = ">" Then
                    If str(counter - 1) <> "/" Then
                        ' fix the missing "/" using Insert() method '
                        str = str.ToString.Insert(counter, " /")
                    End If
                    Exit While
                End If
                counter += 1
            End While
        Next
        Return str.ToString
    End Function
    Private Sub btnEditHTML_Click(sender As Object, e As EventArgs) Handles btnEditHTML.Click
        Rtb.Text = String.Empty
        'the 2 base64 images in the html below are actually just small red dots
        Dim RawHTML As String = "<P>John Doe</P><IMG " &
        "src=""data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR42mP8z8BQDwAEhQGAhKmMIQAAAABJRU5ErkJggg=="">&nbsp;Jackson5<IMG " &
        "src=""data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR42mP8z8BQDwAEhQGAhKmMIQAAAABJRU5ErkJggg=="">"
        Rtb.Text = GetFormattedHTML(RawHTML)
        'notice that the 2nd base64 string is not edited as required. 
    End Sub

    Private Sub btnGenerate_Click(sender As Object, e As EventArgs) Handles btnGenerate.Click
        'here I create a 2 column itextsharp table to parse my html into the cells

        Dim doc As New iTextSharp.text.Document(iTextSharp.text.PageSize.A4, 25, 25, 25, 30)
        Dim wri As PdfWriter = PdfWriter.GetInstance(doc, New System.IO.FileStream(dsktop & "\testtable.pdf", System.IO.FileMode.Create))
        doc.Open()
        'set table columnwidths -------------------------------------------------------------
        Dim MainTable As New PdfPTable(2) '2 column table
        MainTable.WidthPercentage = 100
        Dim Wth(1) As Single
        Dim u As Integer = 2
        For i As Integer = 0 To 1
            Wth(i) = CInt(Math.Floor(2 * 500 / u))
        Next
        MainTable.SetWidths(Wth)

        Dim htmlstr As String = GetFormattedHTML("<P>John Doe</P><IMG " &
        "src=""data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR42mP8z8BQDwAEhQGAhKmMIQAAAABJRU5ErkJggg=="">&nbsp;Jackson5<IMG " &
        "src=""data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR42mP8z8BQDwAEhQGAhKmMIQAAAABJRU5ErkJggg=="">")

        Dim Elmts = New ElementList()
        Elmts = XMLWorkerHelper.ParseToElementList(htmlstr, Nothing)
        Dim MinorTable As New PdfPTable(1)
        MinorTable = SetTable(Elmts, htmlstr)

        For i = 1 To 2
            Dim Cell As New PdfPCell
            Cell.AddElement(MinorTable)
            MainTable.AddCell(Cell)
        Next
        doc.Add(MainTable)
        doc.Close()

        Process.Start(dsktop & "\testtable.pdf")

    End Sub
    Public Function SetTable(ByVal elements As ElementList, ByVal htmlcode As String) As PdfPTable

        Dim tagProcessors As DefaultTagProcessorFactory = CType(Tags.GetHtmlTagProcessorFactory(), DefaultTagProcessorFactory)
        tagProcessors.RemoveProcessor(HTML.Tag.IMG) ' remove the default processor
        tagProcessors.AddProcessor(HTML.Tag.IMG, New CustomImageTagProcessor()) ' use our new processor

        Dim cssResolver As ICSSResolver = XMLWorkerHelper.GetInstance().GetDefaultCssResolver(True)
        cssResolver.AddCssFile(Application.StartupPath & "\pdf.css", True)
        'see sample css file at https://learnwebcode.com/how-to-create-your-first-css-file/

        'Setup Fonts
        Dim xmlFontProvider As XMLWorkerFontProvider = New XMLWorkerFontProvider(XMLWorkerFontProvider.DONTLOOKFORFONTS)
        xmlFontProvider.RegisterDirectory(Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "assets/fonts/"))

        Dim cssAppliers As CssAppliers = New CssAppliersImpl(xmlFontProvider)

        Dim htmlContext As HtmlPipelineContext = New HtmlPipelineContext(cssAppliers)
        htmlContext.SetAcceptUnknown(True)
        htmlContext.SetTagFactory(tagProcessors)

        Dim pdf As ElementHandlerPipeline = New ElementHandlerPipeline(elements, Nothing)
        Dim htmlp As HtmlPipeline = New HtmlPipeline(htmlContext, pdf)
        Dim css As CssResolverPipeline = New CssResolverPipeline(cssResolver, htmlp)

        Dim worker As XMLWorker = New XMLWorker(css, True)
        Dim p As XMLParser = New XMLParser(worker)

        'Dim holderTable As New PdfPTable({1})
        Dim holderTable As PdfPTable = New PdfPTable({1})
        holderTable.WidthPercentage = 100
        holderTable.HorizontalAlignment = Element.ALIGN_LEFT

        Dim holderCell As New PdfPCell()
        holderCell.Padding = 0
        holderCell.UseBorderPadding = False
        holderCell.Border = 0

        p.Parse(New MemoryStream(System.Text.Encoding.ASCII.GetBytes(htmlcode)))

        For Each el As IElement In elements
            holderCell.AddElement(el)
        Next
        holderTable.AddCell(holderCell)
        'Dim holderRow As New PdfPRow({holderCell})
        'holderTable.Rows.Add(holderRow)
        Return holderTable

    End Function

End Class

Public Class CustomImageTagProcessor
    Inherits iTextSharp.tool.xml.html.Image
    Public Overrides Function [End](ctx As IWorkerContext, tag As Tag, currentContent As IList(Of IElement)) As IList(Of IElement)
        Dim attributes As IDictionary(Of String, String) = tag.Attributes
        Dim src As String = String.Empty
        If Not attributes.TryGetValue(iTextSharp.tool.xml.html.HTML.Attribute.SRC, src) Then
            Return New List(Of IElement)(1)
        End If

        If String.IsNullOrEmpty(src) Then
            Return New List(Of IElement)(1)
        End If

        If src.StartsWith("data:image/", StringComparison.InvariantCultureIgnoreCase) Then
            ' data:[<MIME-type>][;charset=<encoding>][;base64],<data>
            Dim base64Data As String = src.Substring(src.IndexOf(",") + 1)
            Dim imagedata As Byte() = Convert.FromBase64String(base64Data)
            Dim image As iTextSharp.text.Image = iTextSharp.text.Image.GetInstance(imagedata)

            Dim list As List(Of IElement) = New List(Of IElement)()
            Dim htmlPipelineContext As pipeline.html.HtmlPipelineContext = GetHtmlPipelineContext(ctx)
            list.Add(GetCssAppliers().Apply(New Chunk(DirectCast(GetCssAppliers().Apply(image, tag, htmlPipelineContext), iTextSharp.text.Image), 0, 0, True), tag, htmlPipelineContext))
            Return list
        Else
            If File.Exists(Path.Combine(AppDomain.CurrentDomain.BaseDirectory, src)) Then
                Dim imagedata As Byte() = File.ReadAllBytes(Path.Combine(AppDomain.CurrentDomain.BaseDirectory, src))
                Dim image As iTextSharp.text.Image = iTextSharp.text.Image.GetInstance(Path.Combine(AppDomain.CurrentDomain.BaseDirectory, src))

                Dim list As List(Of IElement) = New List(Of IElement)()
                Dim htmlPipelineContext As pipeline.html.HtmlPipelineContext = GetHtmlPipelineContext(ctx)
                list.Add(GetCssAppliers().Apply(New Chunk(DirectCast(GetCssAppliers().Apply(image, tag, htmlPipelineContext), iTextSharp.text.Image), 0, 0, True), tag, htmlPipelineContext))
                Return list
            End If
            Return MyBase.[End](ctx, tag, currentContent)
        End If
    End Function
End Class

var doc = new HtmlParser().Parse(html);