这适用于使用iTextSharp 5.5.8或5.5.9，我的测试工具是：
{
PdfReader pdfReader = null;
StringBuilder actual = new StringBuilder();
try
{
pdfReader = new PdfReader(@"Quotation for Macbook 6-16.pdf");
}
catch (iTextSharp.text.exceptions.BadPasswordException bpe)
{
actual.AppendLine(string.Format("Exception: Bad Password {0}", bpe));
}
catch (Exception ex)
{
actual.AppendLine(string.Format("Exception: PDFReader {0}", ex));
}
int pages = pdfReader.NumberOfPages;
for (int page = 1; page <= pages; page++)
{
try
{
String s = PdfTextExtractor.GetTextFromPage(pdfReader, page);
actual.AppendLine(string.Format("{0}", s));
}
catch (Exception ex)
{
actual.AppendLine(string.Format("Exception PDF Page {0}: {1}", page, ex));
}
}
foreach (var field in pdfReader.AcroFields.Fields)
{
actual.AppendLine(string.Format("{0}: {1}", field.Key, pdfReader.AcroFields.GetField(field.Key)));
}
}
我已经处理了数千个调用GetTextFromPage的PDF文件，但遇到了根本没有返回的特定PDF。我从GitHub下载了代码并遍历它处理文件，它看起来像LineDashPattern调用InitFirst时的条件导致这里的连续循环是来自LineDashPattern.cs的代码
private void InitFirst(float phase) {
if (dashArray.Size > 0) {
while (phase > 0) {
phase -= dashArray.GetAsNumber(currentIndex).FloatValue;
currentIndex = (currentIndex + 1) % DashArray.Size;
elemOrdinalNumber++;
}
if (phase < 0) {
--elemOrdinalNumber;
--currentIndex;
currentElem = new DashArrayElem(-phase, IsEven(elemOrdinalNumber));
} else {
currentElem = new DashArrayElem(dashArray.GetAsNumber(currentIndex).FloatValue,
IsEven(elemOrdinalNumber));
}
}
}
传入的阶段是6.44245E + 8，dashArray 28.8中有两个条目，然而9.6相位数如此之大会导致第一个而卡住，因为28.8根据浮动的分辨率来降低相位是不够的。
我对内部的了解不够，或者我会考虑进行更改。
我真的只对提取文本感兴趣，所以如果有设置我可以实现过滤掉对我有用的线处理。
答案 0 :(得分：1)
我更新了LineDashPattern.cs文件。我正在使用iTextSharp，据我所知5.5.9是最新版本，所以iText 7可能是Java。
无论如何，这是我更新的代码。我在类中添加了elts（行元素的总和）作为私有字段，根据当前dashArray更新了elts属性集例程以更新dashArray，最后更新了InitFirst方法，将阶段除以elts在一个语句中进行大量计算，然后落入原始代码中以找到实际元素。
我一般不知道通常会将什么阶段值传递到例程中，但是如果他们可以调整阶段我的值将会循环近1700万次，所以这个变化应该明显更快，因为它被称为多个对于这个PDF来说，它可以提高性能，更不用说解决bug了。完整的文件代码如下：
/*
* $Id$
*
* This file is part of the iText (R) project.
* Copyright (c) 1998-2016 iText Group NV
* Authors: Bruno Lowagie, Paulo Soares, et al.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License version 3
* as published by the Free Software Foundation with the addition of the
* following permission added to Section 15 as permitted in Section 7(a):
* FOR ANY PART OF THE COVERED WORK IN WHICH THE COPYRIGHT IS OWNED BY
* ITEXT GROUP. ITEXT GROUP DISCLAIMS THE WARRANTY OF NON INFRINGEMENT
* OF THIRD PARTY RIGHTS
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE.
* See the GNU Affero General Public License for more details.
* You should have received a copy of the GNU Affero General Public License
* along with this program; if not, see http://www.gnu.org/licenses or write to
* the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
* Boston, MA, 02110-1301 USA, or download the license from the following URL:
* http://itextpdf.com/terms-of-use/
*
* The interactive user interfaces in modified source and object code versions
* of this program must display Appropriate Legal Notices, as required under
* Section 5 of the GNU Affero General Public License.
*
* In accordance with Section 7(b) of the GNU Affero General Public License,
* a covered work must retain the producer line in every PDF that is created
* or manipulated using iText.
*
* You can be released from the requirements of the license by purchasing
* a commercial license. Buying such a license is mandatory as soon as you
* develop commercial activities involving the iText software without
* disclosing the source code of your own applications.
* These activities include: offering paid services to customers as an ASP,
* serving PDFs on the fly in a web application, shipping iText with a closed
* source product.
*
* For more information, please contact iText Software Corp. at this
* address: sales@itextpdf.com
*/
using System.util;
using iTextSharp.awt.geom;
namespace iTextSharp.text.pdf.parser {
/**
* Represents the line dash pattern. The line dash pattern shall control the pattern
* of dashes and gaps used to stroke paths. It shall be specified by a dash array and
* a dash phase.
*
* @since 5.5.6
*/
public class LineDashPattern {
private PdfArray dashArray;
private float dashPhase;
private int currentIndex;
private int elemOrdinalNumber = 1;
private DashArrayElem currentElem;
private float elts = 0.0F;
/**
* Creates new {@link LineDashPattern} object.
* @param dashArray The dash array. See {@link #getDashArray()}
* @param dashPhase The dash phase. See {@link #getDashPhase()}
*/
public LineDashPattern(PdfArray dashArray, float dashPhase) {
this.dashArray = new PdfArray(dashArray);
this.dashPhase = dashPhase;
InitFirst(dashPhase);
}
/**
* Getter and setter for the dash array.
*
* The dash array’s elements is number that specify the lengths of
* alternating dashes and gaps; the numbers are nonnegative. The
* elements are expressed in user space units.
*
* @return The dash array.
*/
public PdfArray DashArray {
get { return dashArray; }
set
{
dashArray = value;
float elts = 0.0F;
for (int i = 0; i < dashArray.Size; i++)
{
elts += dashArray.GetAsNumber(i).FloatValue;
}
}
}
/**
* Getter and setter for the dash phase.
*
* The dash phase shall specify the distance into the dash pattern at which
* to start the dash. The elements are expressed in user space units.
*
* @return The dash phase.
*/
public float DashPhase {
get { return dashPhase; }
set { dashPhase = value; }
}
/**
* Calculates and returns the next element which is either gap or dash.
* @return The next dash array's element.
*/
public DashArrayElem Next() {
DashArrayElem ret = currentElem;
if (dashArray.Size > 0) {
currentIndex = (currentIndex + 1) % DashArray.Size;
currentElem = new DashArrayElem(dashArray.GetAsNumber(currentIndex).FloatValue,
IsEven(++elemOrdinalNumber));
}
return ret;
}
/**
* Checks whether the dashed pattern is solid or not. It's solid when the
* size of a dash array is even and sum of all the units off in the array
* is 0.<br/>
* For example: [3 0 4 0 5 0 6 0] (sum is 0), [3 0 4 0 5 1] (sum is 1).
*/
public bool IsSolid() {
if (dashArray.Size % 2 != 0) {
return false;
}
float unitsOffSum = 0;
for (int i = 1; i < dashArray.Size; i += 2) {
unitsOffSum += dashArray.GetAsNumber(i).FloatValue;
}
return Util.Compare(unitsOffSum, 0) == 0;
}
/**
* Resets the dash array so that the {@link #next()} method will start
* from the beginning of the dash array.
*/
public void Reset() {
currentIndex = 0;
elemOrdinalNumber = 1;
InitFirst(dashPhase);
}
private void InitFirst(float phase) {
if (dashArray.Size > 0) {
// handle a bulk of the line pattern
//
if (elts > 0.0)
{
int occurances = (int)(phase / elts);
elemOrdinalNumber = occurances * dashArray.Size;
phase -= occurances * elts;
// adjust for the final set of pattern elements
//
while (phase > 0)
{
phase -= dashArray.GetAsNumber(currentIndex).FloatValue;
currentIndex = (currentIndex + 1) % DashArray.Size;
elemOrdinalNumber++;
}
if (phase < 0)
{
--elemOrdinalNumber;
--currentIndex;
currentElem = new DashArrayElem(-phase, IsEven(elemOrdinalNumber));
}
else
{
currentElem = new DashArrayElem(dashArray.GetAsNumber(currentIndex).FloatValue,
IsEven(elemOrdinalNumber));
}
}
}
}
private bool IsEven(int num) {
return (num % 2) == 0;
}
public class DashArrayElem {
private float val;
private bool isGap;
public DashArrayElem(float val, bool isGap) {
this.val = val;
this.isGap = isGap;
}
public float Value
{
get { return val; }
set { val = value; }
}
public bool IsGap
{
get { return isGap; }
set { isGap = value; }
}
}
}
}