crop Left side of pdf using Itextsharp - pdf

Question

I am trying to crop left side of pdf to 10 mm. i used below code
public void TrimLeft(string sourceFilePath, string outputFilePath)
{
PdfReader pdfReader = new PdfReader(sourceFilePath);
float width =(float) GetPDFwidth(sourceFilePath);
float height = (float)GetPDFHeight(sourceFilePath);
float widthTo_Trim = iTextSharp.text.Utilities.MillimetersToPoints(10);
// Set which part of the source document will be copied.
// PdfRectangel(bottom-left-x, bottom-left-y, upper-right-x, upper-right-y)
PdfRectangle rect = new PdfRectangle(0, 0, width - widthTo_Trim, height);
PdfRectangle rectLeftside = new PdfRectangle(0,0,width - widthTo_Trim, height);
using (var output = new FileStream(outputFilePath, FileMode.CreateNew, FileAccess.Write))
{
// Create a new document
Document doc = new Document();
// Make a copy of the document
PdfSmartCopy smartCopy = new PdfSmartCopy(doc, output);
// Open the newly created document
doc.Open();
// Loop through all pages of the source document
for (int i = 1; i <= pdfReader.NumberOfPages; i++)
{
// Get a page
var page = pdfReader.GetPageN(i);
// Apply the rectangle filter we created
page.Put(PdfName.CROPBOX, rectLeftside);
page.Put(PdfName.MEDIABOX, rectLeftside);
// Copy the content and insert into the new document
var copiedPage = smartCopy.GetImportedPage(pdfReader, i);
smartCopy.AddPage(copiedPage);
}
// Close the output document
doc.Close();
}
}
Its croping RHS of pdf. i tried with changing the coordinates
PdfRectangle rectLeftside = new PdfRectangle(0,0,width - widthTo_Trim, height);
but unable to get desired result.
How can i crop X mm left side

Answer 1

Making the hint in the comments an actual answer...
You create the new crop box rectangle like this:
PdfRectangle rectLeftside = new PdfRectangle(0,0,width - widthTo_Trim, height);
The constructor in question is:
/**
* Constructs a <CODE>PdfRectangle</CODE>-object.
*
* #param llx lower left x
* #param lly lower left y
* #param urx upper right x
* #param ury upper right y
*/
...
public PdfRectangle(float llx, float lly, float urx, float ury)
Thus, assuming your original PDF has a crop box with lower left coordinates (0,0), your code manipulates the upper right x, i.e. the right side of the box. You, on the other hand, actually want to manipulate the left side. Thus, you should use something like:
PdfRectangle rectLeftside = new PdfRectangle(widthTo_Trim, 0, width, height);
After the hint in comments, this also was the OP's solution.
Additional improvements
Using a PdfStamper
The OP uses a PdfSmartCopy instance and its method GetImportedPage to crop left side of pdf. While this already is better than the use of a plain PdfWriter for this task, the best choice for manipulating a single PDF usually is a PdfStamper: You don't have to copy anything anymore, you merely apply the changes. Furthermore the result internally is more like the original.
Determining boxes page by page
The OP in his code assumes
a constant size of all pages in the PDF (which he determines in his methods GetPDFwidth and GetPDFHeight) and
constant lower left coordinates (0,0) of the current crop box on all pages.
Neither of these assumptions is true for all PDFs. Thus, one should retrieve and manipulate the crop box of each page separately.
The code
public void TrimLeftImproved(string sourceFilePath, string outputFilePath)
{
PdfReader pdfReader = new PdfReader(sourceFilePath);
float widthTo_Trim = iTextSharp.text.Utilities.MillimetersToPoints(10);
using (FileStream output = new FileStream(outputFilePath, FileMode.Create, FileAccess.Write))
using (PdfStamper pdfStamper = new PdfStamper(pdfReader, output))
{
for (int page = 1; page <= pdfReader.NumberOfPages; page++)
{
Rectangle cropBox = pdfReader.GetCropBox(page);
cropBox.Left += widthTo_Trim;
pdfReader.GetPageN(page).Put(PdfName.CROPBOX, new PdfRectangle(cropBox));
}
}
}