crop Left side of pdf using Itextsharp

问题

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

回答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

1. a constant size of all pages in the PDF (which he determines in his methods GetPDFwidth and GetPDFHeight) and
2. 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));
        }
    }
}

来源：https://stackoverflow.com/questions/28171199/crop-left-side-of-pdf-using-itextsharp