使用 itextsharp 从 Pdf 文件中提取文本和文本矩形坐标 [英] Extract text and text rectangle coordinates from a Pdf file using itextsharp
问题描述
我正在尝试从 PDF 文件中获取所有单词及其位置坐标.我已经成功地在 .NET 上使用了 Acrobat API.现在，我尝试使用免费 API 获得相同的结果，例如 iTextSharp(.NET 版本).我可以使用 PRTokeniser 获取文本(逐行)，但我不知道如何获取行的坐标，更不用说每个单词的坐标了.
I'm trying to get all words and their location coordinates from a PDF file. I've succeeded using the Acrobat API on .NET. Now, I'm trying to get the same result using a free API, such as iTextSharp (the .NET version). I can get the text (line by line) with PRTokeniser, but I have no idea of how to get the coordinates of the line, let alone of each word.
推荐答案
我的帐户太新 回复 Mark Storer 的回答.
My account is too new reply to Mark Storer's answer.
我无法直接使用 LocationTextExtracationStrategy(我想我一定是做错了什么).当我使用 LocationTextExtracationStrategy 时，我能够获取文本，但我无法弄清楚如何获取每个字符串(或字符串行)的坐标.
I wasn't able to directly use the LocationTextExtracationStrategy (I think I must be doing something wrong). When I used the LocationTextExtracationStrategy I was able to get the text but I couldn't figure out how to get the coords for each string (or line of strings).
我最终对 LocationTextExtracationStrategy 进行了子类化并公开了我想要的数据，因为它内部确实有这些数据.
I ended up subclassing the LocationTextExtracationStrategy and exposing the data I wanted because it does have it internally.
我也想在 .net 中使用它...所以这是我放在一起的一个草率的 C# 版本.
I also wanted it in .net... so here is a sloppy C# version of what I put together.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using iTextSharp.text.pdf.parser;
namespace PdfHelper
{
/// <summary>
/// Taken from http://www.java-frameworks.com/java/itext/com/itextpdf/text/pdf/parser/LocationTextExtractionStrategy.java.html
/// </summary>
class LocationTextExtractionStrategyEx : LocationTextExtractionStrategy
{
private List<TextChunk> m_locationResult = new List<TextChunk>();
private List<TextInfo> m_TextLocationInfo = new List<TextInfo>();
public List<TextChunk> LocationResult
{
get { return m_locationResult; }
}
public List<TextInfo> TextLocationInfo
{
get { return m_TextLocationInfo; }
}
/// <summary>
/// Creates a new LocationTextExtracationStrategyEx
/// </summary>
public LocationTextExtractionStrategyEx()
{
}
/// <summary>
/// Returns the result so far
/// </summary>
/// <returns>a String with the resulting text</returns>
public override String GetResultantText()
{
m_locationResult.Sort();
StringBuilder sb = new StringBuilder();
TextChunk lastChunk = null;
TextInfo lastTextInfo = null;
foreach (TextChunk chunk in m_locationResult)
{
if (lastChunk == null)
{
sb.Append(chunk.Text);
lastTextInfo = new TextInfo(chunk);
m_TextLocationInfo.Add(lastTextInfo);
}
else
{
if (chunk.sameLine(lastChunk))
{
float dist = chunk.distanceFromEndOf(lastChunk);
if (dist < -chunk.CharSpaceWidth)
{
sb.Append(' ');
lastTextInfo.addSpace();
}
//append a space if the trailing char of the prev string wasn't a space && the 1st char of the current string isn't a space
else if (dist > chunk.CharSpaceWidth / 2.0f && chunk.Text[0] != ' ' && lastChunk.Text[lastChunk.Text.Length - 1] != ' ')
{
sb.Append(' ');
lastTextInfo.addSpace();
}
sb.Append(chunk.Text);
lastTextInfo.appendText(chunk);
}
else
{
sb.Append('
');
sb.Append(chunk.Text);
lastTextInfo = new TextInfo(chunk);
m_TextLocationInfo.Add(lastTextInfo);
}
}
lastChunk = chunk;
}
return sb.ToString();
}
/// <summary>
///
/// </summary>
/// <param name="renderInfo"></param>
public override void RenderText(TextRenderInfo renderInfo)
{
LineSegment segment = renderInfo.GetBaseline();
TextChunk location = new TextChunk(renderInfo.GetText(), segment.GetStartPoint(), segment.GetEndPoint(), renderInfo.GetSingleSpaceWidth(), renderInfo.GetAscentLine(), renderInfo.GetDescentLine());
m_locationResult.Add(location);
}
public class TextChunk : IComparable, ICloneable
{
string m_text;
Vector m_startLocation;
Vector m_endLocation;
Vector m_orientationVector;
int m_orientationMagnitude;
int m_distPerpendicular;
float m_distParallelStart;
float m_distParallelEnd;
float m_charSpaceWidth;
public LineSegment AscentLine;
public LineSegment DecentLine;
public object Clone()
{
TextChunk copy = new TextChunk(m_text, m_startLocation, m_endLocation, m_charSpaceWidth, AscentLine, DecentLine);
return copy;
}
public string Text
{
get { return m_text; }
set { m_text = value; }
}
public float CharSpaceWidth
{
get { return m_charSpaceWidth; }
set { m_charSpaceWidth = value; }
}
public Vector StartLocation
{
get { return m_startLocation; }
set { m_startLocation = value; }
}
public Vector EndLocation
{
get { return m_endLocation; }
set { m_endLocation = value; }
}
/// <summary>
/// Represents a chunk of text, it's orientation, and location relative to the orientation vector
/// </summary>
/// <param name="txt"></param>
/// <param name="startLoc"></param>
/// <param name="endLoc"></param>
/// <param name="charSpaceWidth"></param>
public TextChunk(string txt, Vector startLoc, Vector endLoc, float charSpaceWidth, LineSegment ascentLine, LineSegment decentLine)
{
m_text = txt;
m_startLocation = startLoc;
m_endLocation = endLoc;
m_charSpaceWidth = charSpaceWidth;
AscentLine = ascentLine;
DecentLine = decentLine;
m_orientationVector = m_endLocation.Subtract(m_startLocation).Normalize();
m_orientationMagnitude = (int)(Math.Atan2(m_orientationVector[Vector.I2], m_orientationVector[Vector.I1]) * 1000);
// see http://mathworld.wolfram.com/Point-LineDistance2-Dimensional.html
// the two vectors we are crossing are in the same plane, so the result will be purely
// in the z-axis (out of plane) direction, so we just take the I3 component of the result
Vector origin = new Vector(0, 0, 1);
m_distPerpendicular = (int)(m_startLocation.Subtract(origin)).Cross(m_orientationVector)[Vector.I3];
m_distParallelStart = m_orientationVector.Dot(m_startLocation);
m_distParallelEnd = m_orientationVector.Dot(m_endLocation);
}
/// <summary>
/// true if this location is on the the same line as the other text chunk
/// </summary>
/// <param name="textChunkToCompare">the location to compare to</param>
/// <returns>true if this location is on the the same line as the other</returns>
public bool sameLine(TextChunk textChunkToCompare)
{
if (m_orientationMagnitude != textChunkToCompare.m_orientationMagnitude) return false;
if (m_distPerpendicular != textChunkToCompare.m_distPerpendicular) return false;
return true;
}
/// <summary>
/// Computes the distance between the end of 'other' and the beginning of this chunk
/// in the direction of this chunk's orientation vector. Note that it's a bad idea
/// to call this for chunks that aren't on the same line and orientation, but we don't
/// explicitly check for that condition for performance reasons.
/// </summary>
/// <param name="other"></param>
/// <returns>the number of spaces between the end of 'other' and the beginning of this chunk</returns>
public float distanceFromEndOf(TextChunk other)
{
float distance = m_distParallelStart - other.m_distParallelEnd;
return distance;
}
/// <summary>
/// Compares based on orientation, perpendicular distance, then parallel distance
/// </summary>
/// <param name="obj"></param>
/// <returns></returns>
public int CompareTo(object obj)
{
if (obj == null) throw new ArgumentException("Object is now a TextChunk");
TextChunk rhs = obj as TextChunk;
if (rhs != null)
{
if (this == rhs) return 0;
int rslt;
rslt = m_orientationMagnitude - rhs.m_orientationMagnitude;
if (rslt != 0) return rslt;
rslt = m_distPerpendicular - rhs.m_distPerpendicular;
if (rslt != 0) return rslt;
// note: it's never safe to check floating point numbers for equality, and if two chunks
// are truly right on top of each other, which one comes first or second just doesn't matter
// so we arbitrarily choose this way.
rslt = m_distParallelStart < rhs.m_distParallelStart ? -1 : 1;
return rslt;
}
else
{
throw new ArgumentException("Object is now a TextChunk");
}
}
}
public class TextInfo
{
public Vector TopLeft;
public Vector BottomRight;
private string m_Text;
public string Text
{
get { return m_Text; }
}
/// <summary>
/// Create a TextInfo.
/// </summary>
/// <param name="initialTextChunk"></param>
public TextInfo(TextChunk initialTextChunk)
{
TopLeft = initialTextChunk.AscentLine.GetStartPoint();
BottomRight = initialTextChunk.DecentLine.GetEndPoint();
m_Text = initialTextChunk.Text;
}
/// <summary>
/// Add more text to this TextInfo.
/// </summary>
/// <param name="additionalTextChunk"></param>
public void appendText(TextChunk additionalTextChunk)
{
BottomRight = additionalTextChunk.DecentLine.GetEndPoint();
m_Text += additionalTextChunk.Text;
}
/// <summary>
/// Add a space to the TextInfo. This will leave the endpoint out of sync with the text.
/// The assumtion is that you will add more text after the space which will correct the endpoint.
/// </summary>
public void addSpace()
{
m_Text += ' ';
}
}
}
}
我添加了一个 TextLocationInfo 属性，它返回一个文本行列表 + 这些行的坐标(左上和右下)，可用于为您提供一个边界框.
I added a TextLocationInfo property which hands back a List of lines of text + the coords for those lines (upper left and lower right) which can be used to give you a bounding box.
我在最初玩的时候也看到了一些奇怪的东西.如果我拉了 startPoint & ，看起来我得到了相同的坐标.endPoint 从基线(我认为正确的做法是从 ascentLine 和 DecentLine 中提取这些点).我的初始传球我只是使用了基线.奇怪的是，我没有看到结果坐标有什么不同.所以对谨慎的人来说......我不确定我提供的坐标是否正确......我只是认为它们是/应该是.
I also saw something odd with my initial playing around. It looked like I got the same coords if I pulled the startPoint & endPoint from the baseline (I think the right thing to do, and the thing I did, was to pull those points from ascentLine and DecentLine). My initial pass I just used the baseline. Odd that I didn't see a difference in the resulting coords. So word to the wary... I'm not sure if the coords I'm providing are right... I just think they are/should be.
这篇关于使用 itextsharp 从 Pdf 文件中提取文本和文本矩形坐标的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
