ITextSharp returning same size pdf when I'm trying to compress pdf file with different levels

c#, compression, itext, pdf

Solution

You have a couple of questions and I'll try my best to answer them.

`PdfStamper` is a helper class that ultimately uses another class called `PdfStamperImp` to do most of the work. `PdfStamperImp` is derived from `PdfWriter` and when you use `stamper.Writer` you are actually getting back this implementation class. Many of the properties on `PdfStamper` also pass directly through to the implementation class. So these two calls actually do the same thing.

stamper.SetFullCompression();
stamper.Writer.SetFullCompression();

Another point of confusion is that `SetFullCompression` and the `CompressionLevel` aren't actually related at all. "Full compression" represents a feature that was added in PDF 1.5 called "Object Streams" that allows grouping PDF objects together to potentially allow for greater compression. There's actually no requirement that what we think of as "compression" actually occurs but in reality I think it would always happen. (Possibly a super simple document might get larger with this enabled, not sure and don't feel like testing.)

The `CompressionLevel` is actually what you normally think of as compression, a number from 0 to 9 or -1 to mean default (which currently equals six I think). This property is actually part of the `PdfStream` class which many classes ultimately derive from. This setting doesn't "trickle down", however. Since you are importing a stream from another location via `GetPageContent()` and `SetPageContent()` that specific stream has its own compression settings unrelated to the `Writer`'s compression settings. There's actually a third parameter that you can pass to `SetPageContent()` to set your specific compression level if you want.

reader.SetPageContent(1, reader.GetPageContent(1), PdfStream.BEST_COMPRESSION);

Problem

I'm reading a pdf and injecting some content using itextsharp. The resulting `byte[]` is passed to the method below along with the compression level. ``` public static byte[] method(byte[] pdf,int compressionlevel) { using (MemoryStream outputPdfStream1 = new MemoryStream()) { //PdfReader reader1 = new PdfReader(pdf); //PdfStamper stamper1 = new PdfStamper(reader1, outputPdfStream1); //int level = (int)compressionlevel; //if (level <= 9) // stamper1.Writer.CompressionLevel = (int)compressionlevel; //else // stamper1.Writer.SetFullCompression(); //stamper1.SetFullCompression(); //stamper1.Close(); //byte[] newfile = outputPdfStream1.ToArray(); //return newfile; PdfReader reader = new PdfReader(pdf); PdfStamper stamper = new PdfStamper(reader, outputPdfStream1,PdfWriter.VERSION_1_5); int level = (int)compressionlevel; if (level <= 9) { stamper.Writer.CompressionLevel = level; } else stamper.Writer.SetFullCompression(); int total = reader.NumberOfPages + 1; for (int i = 1; i < total; i++) { reader.SetPageContent(i, reader.GetPageContent(i)); } stamper.SetFullCompression(); stamper.Close(); byte[] newfile = outputPdfStream1.ToArray(); return newfile; } } ``` If I comment `stamper.SetFullCompression();` then this method is returning same size of byte array irrespective of the compression level am passing(am passing from 0 to 9 in each case).. If I uncomment `stamper.SetFullCompression();` this method is returning fully compressed version of the input byte irrespective of the compression level!!! What is the purpose/difference of `stamper.SetFullCompression();` and `stamper.Writer.SetFullCompression();`? What is the correct way to use different compression levels so that I can see different sizes in each case?

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