PDF Compression with iTextSharp [closed]

Answer 1

I am not sure if you are considering other libraries, but you can easily recompress existing images using Docotic.Pdf library (Disclaimer: I work for the company).

Here is some sample code:

static void RecompressExistingImages(string fileName, string outputName)
{
    using (PdfDocument doc = new PdfDocument(fileName))
    {
        foreach (PdfImage image in doc.Images)
            image.RecompressWithGroup4Fax();

        doc.Save(outputName);
    }
}

There are also RecompressWithFlate, RecompressWithGroup3Fax, RecompressWithJpeg and Uncompress methods.

The library will convert color images to bilevel ones if needed. You can specify deflate compression level, JPEG quality etc.

I am also ask you to think twice before using approach suggested by @Alasdair. If you are going to deal with PDF files that weren't created by you than the task is far more complex that it might seem.

To start with, there is great deal of images compressed by codecs other than JPXDecode, JBIG2Decode or DCTDecode. And PDF can also contain inline images.

PDF files saved using newer versions of standard (1.5 or newer) can contain cross-reference streams. It means that reading and updating such files is more complex than just finding/updating some numbers at the end of the file.

So, please, use a PDF library.