itext 7 c# how to clip an existing pdf - itext

Question

let's say I have a bunch of pdf files that I want to migrate into a new pdf. BUT the new pdf file is a table-structured file. And the content of the pdf files should fit in the first cell of a two-column-table.
I am not sure if the approach of working with tables is correct. I am open to any other solutions. All I want is at the end some custom text at the top, followed by pdf content and a checkbox on the right side. (One per pdf content)
What I have so far:
`
PdfDocument pdfDoc = new PdfDocument(new PdfWriter(dest));
Document doc = new Document(pdfDoc, PageSize.A4);
doc.SetMargins(0f, 0f, 18f, 18f);
PdfReader reader = new PdfReader(src);
PdfDocument srcDoc = new PdfDocument(reader);
Table table = new Table(new float[] { 2f, 1f });
PdfFormXObject imagePage = srcDoc.GetFirstPage().CopyAsFormXObject(pdfDoc);
var image = new Image(imagePage);
Cell cell = new Cell().Add(image);
cell.SetHorizontalAlignment(HorizontalAlignment.LEFT);
cell.SetVerticalAlignment(VerticalAlignment.TOP);
table.AddCell(cell);
Table checkTable = new Table(2);
Cell cellCheck1 = new Cell();
cellCheck1.SetNextRenderer(new CheckboxCellRenderer(cellCheck1, "cb1", 0));
cellCheck1.SetHeight(50);
checkTable.AddCell(cellCheck1);
Cell cellCheck2 = new Cell();
cellCheck2.SetNextRenderer(new CheckboxCellRenderer(cellCheck2, "cb2", 1));
cellCheck2.SetHeight(50);
checkTable.AddCell(cellCheck2);
table.AddCell(checkTable);
doc.Add(table);
doc.Close();`
My Problem here is that the pdf content has still its margin. Which completely spoils the design. It is so frustrating, I appreciate any help.

Answer 1

You say
My Problem here is that the pdf content has still its margin. Which completely spoils the design.
PDFs (usually) don't know anything about margins. Thus, you have to detect the margins of the page to import first. You can do this by parsing the page content into an event listener that keeps track of the bounding box of drawing instructions, like the TextMarginFinder. Then you can reduce the source page to those dimensions. This can be done by means of the following method:
PdfPage restrictToText(PdfPage page)
{
TextMarginFinder finder = new TextMarginFinder();
new PdfCanvasProcessor(finder).ProcessPageContent(page);
Rectangle textRect = finder.GetTextRectangle();
page.SetMediaBox(textRect);
page.SetCropBox(textRect);
return page;
}
You apply this method in your code right before you copy the page as form XObject, i.e. you replace
PdfFormXObject imagePage = srcDoc.GetFirstPage().CopyAsFormXObject(pdfDoc);
by
PdfFormXObject imagePage = restrictToText(srcDoc.GetFirstPage()).CopyAsFormXObject(pdfDoc);
This causes the Image this XObject will be embedded in to have the correct size. Unfortunately it will be somewhat mispositioned because the restricted page still has the same coordinate system as the original one, merely its crop box defines a smaller section than before. To fix this, one has to apply an offset, one has to subtract the coordinates of the lower left corner of the page crop box which has become the XObject bounding box. Thus, add after instantiating the Image the following code:
Rectangle bbox = imagePage.GetBBox().ToRectangle();
image.SetProperty(Property.LEFT, -bbox.GetLeft());
image.SetProperty(Property.BOTTOM, -bbox.GetBottom());
image.SetProperty(Property.POSITION, LayoutPosition.RELATIVE);
Now the restricted page is properly positioned in your table cell.
Beware: The TextMarginFinder (as its name indicates) determines the margins by text alone. Thus, if the page contains other contents, too, e.g. decorations like a logo, this logo is ignored and might eventually be cut out. If you want such decorations, too, in your overviews, you have to use a different margin finder class.