如何使用itext和java阅读pdf并获取表格单元格高度

Question

First I have created a pdf using itext and java and put a table and tableCell

 PdfPTable table = new PdfPTable(2);
        table.setWidths(new int[]{1, 2});
        PdfPCell cell;
        table.addCell("Address:");
        cell = new PdfPCell(new Phrase(""));
        cell.setFixedHeight(60);
        table.addCell(cell);  

I have another Program Which read this pdf File

  PdfReader reader = new PdfReader("path_of_previously_created_pdf");

Now i want to get TableCell cell and want to Change cell height cell.setFixedHeight(new_Fixed_Height);

It is possible... if Yes . How?? Thanx in advance

Answer 1

If your PDF contains just that simple 1x2 table, it of course would be possible to implement something that gives you the PDF with a cell hight of you choice.

But I assume it eventually is meant to contain more. Already the code you provided via your google drive included more (more table cells plus form elements), and that code, too, does look unfinished concerning the PDF construction. Thus,...

The direct answer

It is not possible.

First of all the table and cell objects you have while creating the PDF are not present as such in the resulting file, they merely are drawn as a number of lines and some text (or whatever you put into the cells).

Thus, you cannot even retrieve the cells you want to change, let alone change it.

The twisted answer

You could, of course, try and parse the page content stream to find the commands for drawing lines, find those ones among them which were drawn for the cell you are interested in, and try to derive the original cell dimension attributes from the line coordinates. Afterwards you can attempt to move everything below the cell down to create the extra space you want.

Depending on the information you have (Do you know the approximate position of the cell? If not, do you at least know some unique content of it?) reading the current cell height will include some guesswork and much coding because unfortunately the iText parser framework does not yet support parsing path operations.

Essentially you have to enhance the classes in the PDF parser package to also process and emit events for PDF path operators (if you know your way around in iText and the PDF specification that should not take more than a week or two) and create an appropriate event listener to find the lines surrounding the cell position you already know (not more than one day of work). Some iText code analysis will show how the fixed cell height and the distance of the surrounding lines relate.

Most likely, though, this is the smaller part of your work. The bigger part is actually manipulating the page content:

If you are lucky, all your page content is located in a single content stream. In that case you merely have to analyse all the page content again but this time to actually change it. The easiest way would be to enhance the classes in the parser package once again (because they already do much of the necessary math and book-keeping) to signal every command from the content stream with normalized coordinates (this might take a week or two). Based on this information signaled to you built an all new content stream in which you leave everything above your cell, move down everything below, and stretch everything crossing the line on which the bottom border of your cell lies (another week maybe).

If you are less lucky you have to fight with multiple included form xobjects crossing the line. As those xobjects may be used from other streams also, you cannot change them but have to either change a copy or include the xobject content in your newly created stream.

Then what about images crossing the line? or interesting patterns? In that case stretching the cell will utterly distort everything.

And then there are annotations, eg your form fields. You need to shift and stretch them, too.

Thus, while this approach is possible to follow, please be aware that (depending on how generic the solution has to become) its implementation will take someone knowing iText and PDF some months.

An alternative approach

You say in a comment

I am working on Pdf Form.I have created itext form using TextField(MULTILINE TEXT) once. After read this pdf and fill up the form but when the content increases it shows scroll Bar and content hide. My problem is Once i print the pdf it did't print hide content.

Why don't you simply for each set of data build an individual PDF with all the cells big enough for the form contents of the respective data set and copy the field values into this new PDF. This is a fairly simple approach, yet flexible enough to not waste too much space but at the same time not hide content.