Rotate a PDF using Powershell and iTextSharp

Question

I have a Powershell script that uses iTextSharp to extract text from PDF files. One of the files the script downloads comes in sideways, so it needs to be rotated in order for the script to read it.

Here's my function which reads the PDF. I've tested it and it works:

function Get-PdfText {
    [CmdletBinding()]
    [OutputType([string])]
    param (
        [Parameter(Mandatory = $true)]
        [string]
        $Path
    )

    try {
        $reader = New-Object iTextSharp.text.pdf.pdfreader -ArgumentList $Path
    }
    catch {
        throw
    }

    $stringBuilder = New-Object System.Text.StringBuilder

    for ($page = 1; $page -le $reader.NumberOfPages; $page++) {
        $text = [iTextSharp.text.pdf.parser.PdfTextExtractor]::GetTextFromPage($reader, $page)
        $null = $stringBuilder.AppendLine($text) 
    }

    $reader.Close()

    return $stringBuilder.ToString()
}

There is plenty of documentation about how to rotate PDFs in C# and Java, but not Powershell. There's a nice example here, but I don't know how to convert it to Powershell: http://developers.itextpdf.com/question/how-rotate-page-90-degrees

Here's my attempt at converting it:

function RotatePdf90Degrees {
    param (
        [Parameter(Mandatory = $true)]
        [string]
        $Path
    )

    $reader = New-Object iTextSharp.text.pdf.PdfReader -ArgumentList $Path
    $n = $reader.NumberOfPages
    $page #PdfDictionary
    $rotate #PdfNumber
    for ($p = 1; $p -le $n; $p++) {
        $page = $reader.GetPageN($p);
        $rotate = $page.GetAsNumber([iTextSharp.text.pdf.PdfName]::ROTATE);
        if ($rotate -eq $null) {
            $page.put([iTextSharp.text.pdf.PdfName]::ROTATE, [iTextSharp.text.pdf]::PdfNumber(90));
        }
        else {
            $page.put([iTextSharp.text.pdf.PdfName]::ROTATE, [iTextSharp.text.pdf]::PdfNumber(($rotate.IntValue() + 90) % 360));
        }
    }

    $stamper = New-Object iTextSharp.text.pdf.PdfStamper ($reader, [System.IO.StreamWriter] $Path);
    $stamper.Close();
    $reader.Close();
}

Something is wrong on the $page.put() lines. I don't know how to feed that function a proper PdfNumber object.

I've been using this documentation: http://developers.itextpdf.com/reference/package/com.itextpdf.text.pdf

Answer 1

Maybe we're working off different versions of powershell, but the first problem I'm having with your sample function is here,

[iTextSharp.text.pdf.PdfName]::ROTATE;

which throws the following exception:

The field or property: "ca" for type: "iTextSharp.text.pdf.PdfName" differs only in letter casing from the field or property: "CA". The type must be Common Language Specification (CLS) compliant.

Looking at the iTextSharp source code, there are two separate fields as noted in the exception:

• PdfName.CA
• PdfName.ca

Haven't written any powershell in a while, so the simplest workaround was to instantiate a new PdfName object with the same string used for PdfName.ROTATE in the source. Anyway, hopefully the following gets you started:

function Rotate-Pdf {
    [CmdletBinding()]
    param(
        [parameter(Mandatory=$true)] [string]$readerPath
        ,[parameter(Mandatory=$true)] [float]$degrees
    )
    $reader = New-Object iTextSharp.text.pdf.PdfReader($readerPath);
    $rotate = New-Object iTextSharp.text.pdf.PdfName('Rotate');
    $pdfNumber = New-Object iTextSharp.text.pdf.PdfNumber($degrees);
    $pageCount = $reader.NumberOfPages;
    for ($i = 1; $i -le $pageCount; $i++) {
        # $rotation = $reader.GetPageRotation($i);
        $pageDict = $reader.GetPageN($i);
        $pageDict.Put($rotate, $pdfNumber);
    }
    $memoryStream = New-Object System.IO.MemoryStream;
    $stamper = New-Object iTextSharp.text.pdf.PdfStamper($reader, $memoryStream);
    $stamper.Dispose();
    $bytes = $memoryStream.ToArray();
    $memoryStream.Dispose();
    $reader.Dispose();
    return $bytes;
}
$bytes = Rotate-Pdf $input 90;
[System.IO.File]::WriteAllBytes($output, $bytes);

Note that there's an extra parameter for degrees to rotate, and have commented out $reader.GetPageRotation(). Depending on how a PDF is created, you cannot always count on PdfReader.GetPageRotation().

UPDATE:

Confirmed the exception noted above is specific to PowerShell 4.0. Didn't test V3.0, but when using V2.0, [iTextSharp.text.pdf.PdfName]::ROTATE does not throw a ExtendedTypeSystemException, and runs without issue.