Why result of GetPageLabels is different from the Adobe Acrobat - pdf

Question

I edit page number of pdf in Adobe Acrobat X Pro.
Test PDF
result:
1-FrontCover
2-FrontFold
3-i
4-ii
5-iii
6-1
7-2
8-3
9-4
10-5
11-BackFold
12-BackCover
But this result of GetPageLabels is wrong
page number:
0-FrontCover1
1-FrontFold1
2-FrontFoldi
3-FrontFoldii
4-FrontFoldiii
5-FrontFold1
6-FrontFold2
7-FrontFold3
8-FrontFold4
9-FrontFold5
10-BackFold1
11-BackCover1
C# Code:
objLabels = PdfPageLabels.GetPageLabels(objReader);
TextBox1.Text += "page number:" + Environment.NewLine;
if (objLabels != null) {
for (i = 0; i <= objLabels.Length - 1; i++) {
TextBox1.Text += i + "-" + objLabels(i) + Environment.NewLine;
}
}
How to get the correct result like Adobe Acrobat X Pro?

Answer 1

There is a small bug in PdfPageLabels.GetPageLabels(PdfReader). When encountering a new page label dictionary without a P (prefix) entry, it does not reset the current prefix value:
int pagecount = 1;
String prefix = "";
char type = 'D';
for (int i = 0; i < n; i++) {
if (numberTree.ContainsKey(i)) {
PdfDictionary d = (PdfDictionary)PdfReader.GetPdfObjectRelease(numberTree[i]);
if (d.Contains(PdfName.ST)) {
pagecount = ((PdfNumber)d.Get(PdfName.ST)).IntValue;
}
else {
pagecount = 1;
}
if (d.Contains(PdfName.P)) {
prefix = ((PdfString)d.Get(PdfName.P)).ToUnicodeString();
}
if (d.Contains(PdfName.S)) {
type = ((PdfName)d.Get(PdfName.S)).ToString()[1];
}
else {
type = 'e';
}
}
...
}
You can fix this by adding the following else clause to the if in question:
if (d.Contains(PdfName.P)) {
prefix = ((PdfString)d.Get(PdfName.P)).ToUnicodeString();
}
else
{
prefix = "";
}
Whith this change I get I get
page number:
0 - FrontCover
1 - FrontFold
2 - i
3 - ii
4 - iii
5 - 1
6 - 2
7 - 3
8 - 4
9 - 5
10 - BackFold
11 - BackCover
PS: The same issue is present in the Java iText version, tested in ReadPageLabels.java.

Answer 2

Thank you for helping to solve my problem,
Here is my complete program.
public string[] ReadPageLabel(PdfReader objReader, int intPageCount)
{
PdfDictionary objDictionary ;
Dictionary<int, PdfObject> objTree ;
string[] arrLabels ;
int i ;
char chrLabelKind ;
string strLabelPrefix ;
int intLableNumber ;
//PdfPageLabels is wrong
//arrLabels = PdfPageLabels.GetPageLabels(objReader)
arrLabels = new string[intPageCount];
if (objReader.Catalog.Get(PdfName.PAGELABELS) != null) {
objTree = PdfNumberTree.ReadTree(PdfReader.GetPdfObjectRelease(objReader.Catalog.Get(PdfName.PAGELABELS)));
chrLabelKind = 'D';
strLabelPrefix = "";
intLableNumber = 1;
for (i = 0; i <= intPageCount - 1; i++) {
if (objTree.ContainsKey(i)) { //if reset page number
objDictionary = PdfReader.GetPdfObjectRelease(objTree[i]);
//PdfName.S:Number Kind
if (objDictionary.Contains(PdfName.S)) {
chrLabelKind = ((PdfName)objDictionary.Get(PdfName.S)).ToString()(1);
//PdfName.S:/R,/r,/A,/a,/e,/D,ToString()(1)get alphabet of Index=1
} else {
chrLabelKind = 'e';
}
//PdfName.P:Prefix
if (objDictionary.Contains(PdfName.P)) {
strLabelPrefix = ((PdfString)objDictionary.Get(PdfName.P)).ToUnicodeString();
} else {
strLabelPrefix = "";
}
//PdfName.ST:Start Number
if (objDictionary.Contains(PdfName.ST)) {
intLableNumber = ((PdfNumber)objDictionary.Get(PdfName.ST)).IntValue;
} else {
intLableNumber = 1;
}
}
switch (chrLabelKind) {
case 'R':
//I,II,III
arrLabels[i] = strLabelPrefix + factories.RomanNumberFactory.GetUpperCaseString(intLableNumber);
break;
case 'r':
//i,ii,iii
arrLabels[i] = strLabelPrefix + factories.RomanNumberFactory.GetLowerCaseString(intLableNumber);
break;
case 'A':
//A,B,C
arrLabels[i] = strLabelPrefix + factories.RomanAlphabetFactory.GetUpperCaseString(intLableNumber);
break;
case 'a':
//a,b,c
arrLabels[i] = strLabelPrefix + factories.RomanAlphabetFactory.GetLowerCaseString(intLableNumber);
break;
case 'e':
//no number kind
arrLabels[i] = strLabelPrefix;
break;
default:
//1,2,3
arrLabels[i] = strLabelPrefix + intLableNumber;
break;
}
intLableNumber += 1;
}
} else {
for (i = 0; i <= intPageCount - 1; i++) {
arrLabels[i] = i + 1;
}
}
return arrLabels;
}