iTextSharp 获取对图形标记的引用
iTextSharp get reference to a graphic markup
我已经研究了几个小时如何做到这一点，但遇到了困难。我有一个 PDF 文件，其中一个对象是指北针。它是一个简单的线条图形（我相信它们在 Acrobat 中被称为图形标记）将表示 "up" 的方向。我想阅读该线条图并确定其旋转。我采取的第一步是查看是否可以使用以下代码枚举 PDF 的内容：
Imports it = iTextSharp.text
Imports ip = iTextSharp.text.pdf
Dim pdfRdr As New ip.PdfReader("C:\city.pdf")
Dim page As ip.PdfDictionary = pdfRdr.GetPageN(1)
Dim objectReference As ip.PdfIndirectReference = CType(page.Get(ip.PdfName.CONTENTS), ip.PdfIndirectReference)
Dim stream As ip.PRStream = CType(ip.PdfReader.GetPdfObject(objectReference), ip.PRStream)
Dim streamBytes() As Byte = ip.PdfReader.GetStreamBytes(stream)
Dim tokenizer As New ip.PRTokeniser(New ip.RandomAccessFileOrArray(streamBytes))
'Loop through each PDf token
While tokenizer.NextToken
Debug.Print("token of type={0} and value={1}", tokenizer.TokenType.ToString, tokenizer.StringValue)
End While
我确实得到了一些数据，但恐怕我只是不知道如何破译它。
token of type=OTHER and value=q
token of type=NUMBER and value=0.86275
token of type=NUMBER and value=0
token of type=NUMBER and value=0
token of type=NUMBER and value=0.86275
token of type=NUMBER and value=54
token of type=NUMBER and value=30
token of type=OTHER and value=cm
token of type=NAME and value=Fm0
token of type=OTHER and value=Do
token of type=OTHER and value=Q
token of type=OTHER and value=q
token of type=NUMBER and value=1
token of type=NUMBER and value=0
token of type=NUMBER and value=0
token of type=NUMBER and value=1
token of type=NUMBER and value=54
token of type=NUMBER and value=18
token of type=OTHER and value=cm
token of type=NAME and value=Fm1
token of type=OTHER and value=Do
token of type=OTHER and value=Q
我已将 PDF 缩减为仅显示我感兴趣的图形。
测试文件在这里https://drive.google.com/file/d/1dYFkvLMvznsx6sN-1GsNZVIBtDpgzwCU/view?usp=sharing
我走的路是正确的还是有不同的方法来获取对图形标记的引用？
I believe they are called Graphic Markups in Acrobat
也许您可以 post PDF 示例？这很重要。
你可以很简单地得到一条线注释的旋转：在页面上循环注释，看注释是否是一条线注释，得到它的坐标，然后计算相对于水平轴的旋转。
使用如下所示的 iText：
PdfReader reader = new PdfReader(INPUT_FILE);
PdfDocument pdfDocument = new PdfDocument(reader);
PdfDictionary firstPage = pdfDocument.getFirstPage().getPdfObject();
PdfArray annots = firstPage.getAsArray(PdfName.Annots);
if (annots != null) {
for (int x = 0; x < annots.size(); x++) {
if (annots.get(x).isDictionary() && annots.getAsDictionary(x).getAsName(PdfName.Subtype) == PdfName.Line) {
PdfArray coordinates = annots.getAsDictionary(x).getAsArray(PdfName.L);
float x2 = coordinates.getAsNumber(0).floatValue();
float y2 = coordinates.getAsNumber(1).floatValue();
float x1 = coordinates.getAsNumber(2).floatValue();
float y1 = coordinates.getAsNumber(3).floatValue();
double deltaY = y2 - y1;
double deltaX = x2 - x1;
double angle = Math.atan2(deltaY , deltaX) * 180 / Math.PI;
System.out.println(angle);
}
}
}
如果您使用的是 iText 5，annots 的获取方式可能略有不同，但其他内容应该大致相同。这是在 5 中获得它的方法：
PdfReader reader = new PdfReader(src);
PdfDictionary firstPage = reader.getPageN(1);
PdfArray annots = firstPage.getAsArray(PdfName.ANNOTS);
这是我的 PDF：
注意线条是线条注释：
这是我的输出：
131.9086081625848
90.0
这看起来是正确的。第一行与横轴成132度，第二行与横轴成90度。
如果这些不是线条注释，问题就会变得更加棘手，因为您必须像以前一样在图形流中跟踪线条操作。如果是这种情况，则有两个明显的问题：
- 您必须以某种方式知道绘制的线是您想要的线。
- 您必须了解整个图形状态上下文（转换和您当前所在的位置）。
与最初的印象相反，指北针不在 PDF 的注释中，而是常规页面内容的一部分。 （@Jon 根据最初的印象创建了他的答案。）
OP分享的PDF中，箭头是直接页面内容的一部分。另一方面，在 OP 共享的 Adobe Acrobat 屏幕截图中，箭头似乎采用 XObject 形式（反过来将从直接页面内容中引用）。
以下方法应该检索两种情况下的矢量图形指令。
您可以使用 iText 解析器框架检索绘制箭头的矢量图形指令。
使用当前的 iText 5.5.x，例如，您需要实现 IExtRenderListener 并在 PdfReaderContentParser 执行中使用该实现，例如：
Public Class VectorParser
Implements IExtRenderListener
Public Sub ModifyPath(renderInfo As PathConstructionRenderInfo) Implements IExtRenderListener.ModifyPath
pathInfos.Add(renderInfo)
End Sub
Public Function RenderPath(renderInfo As PathPaintingRenderInfo) As parser.Path Implements IExtRenderListener.RenderPath
Dim GraphicsState As GraphicsState = getGraphicsState(renderInfo)
Dim ctm As Matrix = GraphicsState.GetCtm()
If (Not (renderInfo.Operation And PathPaintingRenderInfo.FILL) = 0) Then
Console.Write("FILL ({0}) ", ToString(GraphicsState.FillColor))
If (Not (renderInfo.Operation And PathPaintingRenderInfo.STROKE) = 0) Then
Console.Write("and ")
End If
End If
If (Not (renderInfo.Operation And PathPaintingRenderInfo.STROKE) = 0) Then
Console.Write("STROKE ({0}) ", ToString(GraphicsState.StrokeColor))
End If
Console.Write("the path ")
For Each pathConstructionRenderInfo In pathInfos
Select Case pathConstructionRenderInfo.Operation
Case PathConstructionRenderInfo.MOVETO
Console.Write("move to {0} ", ToString(transform(ctm, pathConstructionRenderInfo.SegmentData)))
Case PathConstructionRenderInfo.CLOSE
Console.Write("close {0} ", ToString(transform(ctm, pathConstructionRenderInfo.SegmentData)))
Case PathConstructionRenderInfo.CURVE_123
Console.Write("curve123 {0} ", ToString(transform(ctm, pathConstructionRenderInfo.SegmentData)))
Case PathConstructionRenderInfo.CURVE_13
Console.Write("curve13 {0} ", ToString(transform(ctm, pathConstructionRenderInfo.SegmentData)))
Case PathConstructionRenderInfo.CURVE_23
Console.Write("curve23 {0} ", ToString(transform(ctm, pathConstructionRenderInfo.SegmentData)))
Case PathConstructionRenderInfo.LINETO
Console.Write("line to {0} ", ToString(transform(ctm, pathConstructionRenderInfo.SegmentData)))
Case PathConstructionRenderInfo.RECT
Console.Write("rectangle {0} ", ToString(transform(ctm, expandRectangleCoordinates(pathConstructionRenderInfo.SegmentData))))
End Select
Next
Console.WriteLine()
pathInfos.Clear()
Return Nothing
End Function
Public Sub ClipPath(rule As Integer) Implements IExtRenderListener.ClipPath
End Sub
Public Sub BeginTextBlock() Implements IRenderListener.BeginTextBlock
End Sub
Public Sub RenderText(renderInfo As TextRenderInfo) Implements IRenderListener.RenderText
End Sub
Public Sub EndTextBlock() Implements IRenderListener.EndTextBlock
End Sub
Public Sub RenderImage(renderInfo As ImageRenderInfo) Implements IRenderListener.RenderImage
End Sub
Function expandRectangleCoordinates(rectangle As IList(Of Single)) As List(Of Single)
If rectangle.Count < 4 Then
Return New List(Of Single)
End If
Return New List(Of Single)() From
{
rectangle(0), rectangle(1),
rectangle(0) + rectangle(2), rectangle(1),
rectangle(0) + rectangle(2), rectangle(1) + rectangle(3),
rectangle(0), rectangle(1) + rectangle(3)
}
End Function
Function transform(ctm As Matrix, coordinates As IList(Of Single)) As List(Of Single)
Dim result As List(Of Single) = New List(Of Single)
If Not coordinates Is Nothing Then
For i = 0 To coordinates.Count - 1 Step 2
Dim vector As Vector = New Vector(coordinates(i), coordinates(i + 1), 1)
vector = vector.Cross(ctm)
result.Add(vector(Vector.I1))
result.Add(vector(Vector.I2))
Next
End If
Return result
End Function
Public Function ToString(coordinates As IList(Of Single)) As String
Dim result As StringBuilder = New StringBuilder()
result.Append("[ ")
For i = 0 To coordinates.Count - 1
result.Append(coordinates(i))
result.Append(" ")
Next
result.Append("]")
Return result.ToString()
End Function
Public Function ToString(baseColor As BaseColor) As String
If (baseColor Is Nothing) Then
Return "DEFAULT"
End If
Return String.Format("{0},{1},{2}", baseColor.R, baseColor.G, baseColor.B)
End Function
Function getGraphicsState(renderInfo As PathPaintingRenderInfo) As GraphicsState
Dim gsField As Reflection.FieldInfo = GetType(PathPaintingRenderInfo).GetField("gs", Reflection.BindingFlags.NonPublic Or Reflection.BindingFlags.Instance)
Return CType(gsField.GetValue(renderInfo), GraphicsState)
End Function
Dim pathInfos As List(Of PathConstructionRenderInfo) = New List(Of PathConstructionRenderInfo)
End Class
这样用的
Using pdfReader As New PdfReader("test.pdf")
Dim extRenderListener As IExtRenderListener = New VectorParser
For page = 1 To pdfReader.NumberOfPages
Console.Write(vbCrLf + "Page {0}" + vbCrLf + "====" + vbCrLf, page)
Dim parser As PdfReaderContentParser = New PdfReaderContentParser(pdfReader)
parser.ProcessContent(page, extRenderListener)
Next
End Using
为您的共享文档returns
Page 1
====
STROKE (0,0,255) the path move to [ 277,359 434,2797 ] line to [ 311,5242 434,2797 ]
STROKE (0,0,255) the path move to [ 277,3591 434,2797 ] line to [ 315,0443 424,1336 ]
STROKE (0,0,255) the path move to [ 304,2772 425,376 ] line to [ 304,4842 426,6183 ]
STROKE (0,0,255) the path move to [ 304,6913 426,2042 ] line to [ 310,075 425,376 ]
STROKE (0,0,255) the path move to [ 304,6913 426,8254 ] line to [ 307,5902 425,9972 ]
FILL (0,0,255) the path move to [ 303,656 425,3759 ] line to [ 303,656 425,3759 ] line to [ 306,1407 425,1689 ] line to [ 306,1407 425,1689 ]
STROKE (0,0,255) the path move to [ 303,656 425,376 ] line to [ 303,656 425,376 ] line to [ 306,1407 425,1689 ] line to [ 306,1407 425,1689 ] close [ ]
FILL (0,0,255) the path move to [ 306,969 424,9618 ] line to [ 306,969 424,9618 ] line to [ 309,4538 424,7548 ] line to [ 309,4538 424,7548 ]
STROKE (0,0,255) the path move to [ 306,969 424,9619 ] line to [ 306,969 424,9619 ] line to [ 309,4538 424,7548 ] line to [ 309,4538 424,7548 ] close [ ]
FILL (0,0,255) the path move to [ 309,8679 424,9618 ] line to [ 309,8679 424,9618 ] line to [ 312,3527 424,5477 ] line to [ 312,3527 424,5477 ]
STROKE (0,0,255) the path move to [ 309,868 424,9619 ] line to [ 309,868 424,9619 ] line to [ 312,3527 424,5477 ] line to [ 312,3527 424,5477 ] close [ ]
STROKE (0,0,255) the path move to [ 313,1809 424,3407 ] line to [ 314,8374 424,1336 ]
STROKE (0,0,255) the path move to [ 304,2772 425,7901 ] line to [ 309,8679 424,9619 ] line to [ 312,9738 424,7548 ]
STROKE (0,0,255) the path move to [ 304,2772 425,9972 ] line to [ 309,8679 425,1689 ] line to [ 311,5244 424,9619 ]
STROKE (0,0,255) the path move to [ 304,6914 426,8254 ] line to [ 315,0445 424,1336 ]
STROKE (0,0,255) the path move to [ 311,7315 435,7292 ] line to [ 311,7315 432,8303 ]
STROKE (0,0,255) the path move to [ 321,2564 434,2797 ] line to [ 315,4587 434,2797 ]
STROKE (0,0,255) the path move to [ 315,4586 434,2797 ] line to [ 311,7315 434,2797 ]
STROKE (0,0,255) the path move to [ 311,7315 434,6938 ] line to [ 317,7363 434,0727 ] line to [ 311,7315 433,6585 ]
STROKE (0,0,255) the path move to [ 311,7315 434,4868 ] line to [ 314,8374 434,2797 ] line to [ 311,7315 434,2797 ]
STROKE (0,0,255) the path move to [ 310,6963 436,1433 ] line to [ 317,3222 434,9009 ] line to [ 322,2917 434,2797 ] line to [ 317,3222 433,6585 ] line to [ 310,6963 432,6232 ]
STROKE (0,0,255) the path move to [ 311,7315 435,5221 ] line to [ 317,3222 434,6938 ] line to [ 321,0493 434,2797 ] line to [ 317,3222 433,8656 ] line to [ 311,7315 433,0374 ]
STROKE (0,0,255) the path move to [ 311,7315 435,108 ] line to [ 317,3222 434,4868 ] line to [ 319,3928 434,2797 ] line to [ 317,3222 434,2797 ] line to [ 311,7315 433,4515 ]
这看起来像是一个简单箭头的很多说明，但放大 PDF 可以看到箭头确实是由许多小线构成的：
特别是箭头看起来像是有人用不同长度和宽度的线段手工创建的。
上面的代码本质上是 Java 和 iText 5.5.x 在 .
中的匿名 ExtRenderListener 实现的移植
使用 iText 7 实现同样简单。
顺便说一句：不幸的是，绘制箭头的说明没有特别标记；如果同一页面上有其他矢量图形，则必须按某些特定条件过滤解析器返回的结果，例如颜色（在手头的情况下是纯 RGB 蓝色）或近似坐标范围（例如，仅在给定的 x 和 y 坐标范围内）。
我已经研究了几个小时如何做到这一点，但遇到了困难。我有一个 PDF 文件，其中一个对象是指北针。它是一个简单的线条图形（我相信它们在 Acrobat 中被称为图形标记）将表示 "up" 的方向。我想阅读该线条图并确定其旋转。我采取的第一步是查看是否可以使用以下代码枚举 PDF 的内容：
Imports it = iTextSharp.text
Imports ip = iTextSharp.text.pdf
Dim pdfRdr As New ip.PdfReader("C:\city.pdf")
Dim page As ip.PdfDictionary = pdfRdr.GetPageN(1)
Dim objectReference As ip.PdfIndirectReference = CType(page.Get(ip.PdfName.CONTENTS), ip.PdfIndirectReference)
Dim stream As ip.PRStream = CType(ip.PdfReader.GetPdfObject(objectReference), ip.PRStream)
Dim streamBytes() As Byte = ip.PdfReader.GetStreamBytes(stream)
Dim tokenizer As New ip.PRTokeniser(New ip.RandomAccessFileOrArray(streamBytes))
'Loop through each PDf token
While tokenizer.NextToken
Debug.Print("token of type={0} and value={1}", tokenizer.TokenType.ToString, tokenizer.StringValue)
End While
我确实得到了一些数据，但恐怕我只是不知道如何破译它。
token of type=OTHER and value=q
token of type=NUMBER and value=0.86275
token of type=NUMBER and value=0
token of type=NUMBER and value=0
token of type=NUMBER and value=0.86275
token of type=NUMBER and value=54
token of type=NUMBER and value=30
token of type=OTHER and value=cm
token of type=NAME and value=Fm0
token of type=OTHER and value=Do
token of type=OTHER and value=Q
token of type=OTHER and value=q
token of type=NUMBER and value=1
token of type=NUMBER and value=0
token of type=NUMBER and value=0
token of type=NUMBER and value=1
token of type=NUMBER and value=54
token of type=NUMBER and value=18
token of type=OTHER and value=cm
token of type=NAME and value=Fm1
token of type=OTHER and value=Do
token of type=OTHER and value=Q
我已将 PDF 缩减为仅显示我感兴趣的图形。
测试文件在这里https://drive.google.com/file/d/1dYFkvLMvznsx6sN-1GsNZVIBtDpgzwCU/view?usp=sharing
我走的路是正确的还是有不同的方法来获取对图形标记的引用？
I believe they are called Graphic Markups in Acrobat
也许您可以 post PDF 示例？这很重要。
你可以很简单地得到一条线注释的旋转：在页面上循环注释，看注释是否是一条线注释，得到它的坐标，然后计算相对于水平轴的旋转。
使用如下所示的 iText：
PdfReader reader = new PdfReader(INPUT_FILE);
PdfDocument pdfDocument = new PdfDocument(reader);
PdfDictionary firstPage = pdfDocument.getFirstPage().getPdfObject();
PdfArray annots = firstPage.getAsArray(PdfName.Annots);
if (annots != null) {
for (int x = 0; x < annots.size(); x++) {
if (annots.get(x).isDictionary() && annots.getAsDictionary(x).getAsName(PdfName.Subtype) == PdfName.Line) {
PdfArray coordinates = annots.getAsDictionary(x).getAsArray(PdfName.L);
float x2 = coordinates.getAsNumber(0).floatValue();
float y2 = coordinates.getAsNumber(1).floatValue();
float x1 = coordinates.getAsNumber(2).floatValue();
float y1 = coordinates.getAsNumber(3).floatValue();
double deltaY = y2 - y1;
double deltaX = x2 - x1;
double angle = Math.atan2(deltaY , deltaX) * 180 / Math.PI;
System.out.println(angle);
}
}
}
如果您使用的是 iText 5，annots 的获取方式可能略有不同，但其他内容应该大致相同。这是在 5 中获得它的方法：
PdfReader reader = new PdfReader(src);
PdfDictionary firstPage = reader.getPageN(1);
PdfArray annots = firstPage.getAsArray(PdfName.ANNOTS);
这是我的 PDF：
注意线条是线条注释：
这是我的输出：
131.9086081625848
90.0
这看起来是正确的。第一行与横轴成132度，第二行与横轴成90度。
如果这些不是线条注释，问题就会变得更加棘手，因为您必须像以前一样在图形流中跟踪线条操作。如果是这种情况，则有两个明显的问题：
- 您必须以某种方式知道绘制的线是您想要的线。
- 您必须了解整个图形状态上下文（转换和您当前所在的位置）。
与最初的印象相反，指北针不在 PDF 的注释中，而是常规页面内容的一部分。 （@Jon 根据最初的印象创建了他的答案。）
OP分享的PDF中，箭头是直接页面内容的一部分。另一方面，在 OP 共享的 Adobe Acrobat 屏幕截图中，箭头似乎采用 XObject 形式（反过来将从直接页面内容中引用）。
以下方法应该检索两种情况下的矢量图形指令。
您可以使用 iText 解析器框架检索绘制箭头的矢量图形指令。
使用当前的 iText 5.5.x，例如，您需要实现 IExtRenderListener 并在 PdfReaderContentParser 执行中使用该实现，例如：
Public Class VectorParser
Implements IExtRenderListener
Public Sub ModifyPath(renderInfo As PathConstructionRenderInfo) Implements IExtRenderListener.ModifyPath
pathInfos.Add(renderInfo)
End Sub
Public Function RenderPath(renderInfo As PathPaintingRenderInfo) As parser.Path Implements IExtRenderListener.RenderPath
Dim GraphicsState As GraphicsState = getGraphicsState(renderInfo)
Dim ctm As Matrix = GraphicsState.GetCtm()
If (Not (renderInfo.Operation And PathPaintingRenderInfo.FILL) = 0) Then
Console.Write("FILL ({0}) ", ToString(GraphicsState.FillColor))
If (Not (renderInfo.Operation And PathPaintingRenderInfo.STROKE) = 0) Then
Console.Write("and ")
End If
End If
If (Not (renderInfo.Operation And PathPaintingRenderInfo.STROKE) = 0) Then
Console.Write("STROKE ({0}) ", ToString(GraphicsState.StrokeColor))
End If
Console.Write("the path ")
For Each pathConstructionRenderInfo In pathInfos
Select Case pathConstructionRenderInfo.Operation
Case PathConstructionRenderInfo.MOVETO
Console.Write("move to {0} ", ToString(transform(ctm, pathConstructionRenderInfo.SegmentData)))
Case PathConstructionRenderInfo.CLOSE
Console.Write("close {0} ", ToString(transform(ctm, pathConstructionRenderInfo.SegmentData)))
Case PathConstructionRenderInfo.CURVE_123
Console.Write("curve123 {0} ", ToString(transform(ctm, pathConstructionRenderInfo.SegmentData)))
Case PathConstructionRenderInfo.CURVE_13
Console.Write("curve13 {0} ", ToString(transform(ctm, pathConstructionRenderInfo.SegmentData)))
Case PathConstructionRenderInfo.CURVE_23
Console.Write("curve23 {0} ", ToString(transform(ctm, pathConstructionRenderInfo.SegmentData)))
Case PathConstructionRenderInfo.LINETO
Console.Write("line to {0} ", ToString(transform(ctm, pathConstructionRenderInfo.SegmentData)))
Case PathConstructionRenderInfo.RECT
Console.Write("rectangle {0} ", ToString(transform(ctm, expandRectangleCoordinates(pathConstructionRenderInfo.SegmentData))))
End Select
Next
Console.WriteLine()
pathInfos.Clear()
Return Nothing
End Function
Public Sub ClipPath(rule As Integer) Implements IExtRenderListener.ClipPath
End Sub
Public Sub BeginTextBlock() Implements IRenderListener.BeginTextBlock
End Sub
Public Sub RenderText(renderInfo As TextRenderInfo) Implements IRenderListener.RenderText
End Sub
Public Sub EndTextBlock() Implements IRenderListener.EndTextBlock
End Sub
Public Sub RenderImage(renderInfo As ImageRenderInfo) Implements IRenderListener.RenderImage
End Sub
Function expandRectangleCoordinates(rectangle As IList(Of Single)) As List(Of Single)
If rectangle.Count < 4 Then
Return New List(Of Single)
End If
Return New List(Of Single)() From
{
rectangle(0), rectangle(1),
rectangle(0) + rectangle(2), rectangle(1),
rectangle(0) + rectangle(2), rectangle(1) + rectangle(3),
rectangle(0), rectangle(1) + rectangle(3)
}
End Function
Function transform(ctm As Matrix, coordinates As IList(Of Single)) As List(Of Single)
Dim result As List(Of Single) = New List(Of Single)
If Not coordinates Is Nothing Then
For i = 0 To coordinates.Count - 1 Step 2
Dim vector As Vector = New Vector(coordinates(i), coordinates(i + 1), 1)
vector = vector.Cross(ctm)
result.Add(vector(Vector.I1))
result.Add(vector(Vector.I2))
Next
End If
Return result
End Function
Public Function ToString(coordinates As IList(Of Single)) As String
Dim result As StringBuilder = New StringBuilder()
result.Append("[ ")
For i = 0 To coordinates.Count - 1
result.Append(coordinates(i))
result.Append(" ")
Next
result.Append("]")
Return result.ToString()
End Function
Public Function ToString(baseColor As BaseColor) As String
If (baseColor Is Nothing) Then
Return "DEFAULT"
End If
Return String.Format("{0},{1},{2}", baseColor.R, baseColor.G, baseColor.B)
End Function
Function getGraphicsState(renderInfo As PathPaintingRenderInfo) As GraphicsState
Dim gsField As Reflection.FieldInfo = GetType(PathPaintingRenderInfo).GetField("gs", Reflection.BindingFlags.NonPublic Or Reflection.BindingFlags.Instance)
Return CType(gsField.GetValue(renderInfo), GraphicsState)
End Function
Dim pathInfos As List(Of PathConstructionRenderInfo) = New List(Of PathConstructionRenderInfo)
End Class
这样用的
Using pdfReader As New PdfReader("test.pdf")
Dim extRenderListener As IExtRenderListener = New VectorParser
For page = 1 To pdfReader.NumberOfPages
Console.Write(vbCrLf + "Page {0}" + vbCrLf + "====" + vbCrLf, page)
Dim parser As PdfReaderContentParser = New PdfReaderContentParser(pdfReader)
parser.ProcessContent(page, extRenderListener)
Next
End Using
为您的共享文档returns
Page 1
====
STROKE (0,0,255) the path move to [ 277,359 434,2797 ] line to [ 311,5242 434,2797 ]
STROKE (0,0,255) the path move to [ 277,3591 434,2797 ] line to [ 315,0443 424,1336 ]
STROKE (0,0,255) the path move to [ 304,2772 425,376 ] line to [ 304,4842 426,6183 ]
STROKE (0,0,255) the path move to [ 304,6913 426,2042 ] line to [ 310,075 425,376 ]
STROKE (0,0,255) the path move to [ 304,6913 426,8254 ] line to [ 307,5902 425,9972 ]
FILL (0,0,255) the path move to [ 303,656 425,3759 ] line to [ 303,656 425,3759 ] line to [ 306,1407 425,1689 ] line to [ 306,1407 425,1689 ]
STROKE (0,0,255) the path move to [ 303,656 425,376 ] line to [ 303,656 425,376 ] line to [ 306,1407 425,1689 ] line to [ 306,1407 425,1689 ] close [ ]
FILL (0,0,255) the path move to [ 306,969 424,9618 ] line to [ 306,969 424,9618 ] line to [ 309,4538 424,7548 ] line to [ 309,4538 424,7548 ]
STROKE (0,0,255) the path move to [ 306,969 424,9619 ] line to [ 306,969 424,9619 ] line to [ 309,4538 424,7548 ] line to [ 309,4538 424,7548 ] close [ ]
FILL (0,0,255) the path move to [ 309,8679 424,9618 ] line to [ 309,8679 424,9618 ] line to [ 312,3527 424,5477 ] line to [ 312,3527 424,5477 ]
STROKE (0,0,255) the path move to [ 309,868 424,9619 ] line to [ 309,868 424,9619 ] line to [ 312,3527 424,5477 ] line to [ 312,3527 424,5477 ] close [ ]
STROKE (0,0,255) the path move to [ 313,1809 424,3407 ] line to [ 314,8374 424,1336 ]
STROKE (0,0,255) the path move to [ 304,2772 425,7901 ] line to [ 309,8679 424,9619 ] line to [ 312,9738 424,7548 ]
STROKE (0,0,255) the path move to [ 304,2772 425,9972 ] line to [ 309,8679 425,1689 ] line to [ 311,5244 424,9619 ]
STROKE (0,0,255) the path move to [ 304,6914 426,8254 ] line to [ 315,0445 424,1336 ]
STROKE (0,0,255) the path move to [ 311,7315 435,7292 ] line to [ 311,7315 432,8303 ]
STROKE (0,0,255) the path move to [ 321,2564 434,2797 ] line to [ 315,4587 434,2797 ]
STROKE (0,0,255) the path move to [ 315,4586 434,2797 ] line to [ 311,7315 434,2797 ]
STROKE (0,0,255) the path move to [ 311,7315 434,6938 ] line to [ 317,7363 434,0727 ] line to [ 311,7315 433,6585 ]
STROKE (0,0,255) the path move to [ 311,7315 434,4868 ] line to [ 314,8374 434,2797 ] line to [ 311,7315 434,2797 ]
STROKE (0,0,255) the path move to [ 310,6963 436,1433 ] line to [ 317,3222 434,9009 ] line to [ 322,2917 434,2797 ] line to [ 317,3222 433,6585 ] line to [ 310,6963 432,6232 ]
STROKE (0,0,255) the path move to [ 311,7315 435,5221 ] line to [ 317,3222 434,6938 ] line to [ 321,0493 434,2797 ] line to [ 317,3222 433,8656 ] line to [ 311,7315 433,0374 ]
STROKE (0,0,255) the path move to [ 311,7315 435,108 ] line to [ 317,3222 434,4868 ] line to [ 319,3928 434,2797 ] line to [ 317,3222 434,2797 ] line to [ 311,7315 433,4515 ]
这看起来像是一个简单箭头的很多说明，但放大 PDF 可以看到箭头确实是由许多小线构成的：
特别是箭头看起来像是有人用不同长度和宽度的线段手工创建的。
上面的代码本质上是 Java 和 iText 5.5.x 在
ExtRenderListener 实现的移植
使用 iText 7 实现同样简单。
顺便说一句：不幸的是，绘制箭头的说明没有特别标记；如果同一页面上有其他矢量图形，则必须按某些特定条件过滤解析器返回的结果，例如颜色（在手头的情况下是纯 RGB 蓝色）或近似坐标范围（例如，仅在给定的 x 和 y 坐标范围内）。