I am trying to print an RDL report with terms and conditions PDF. The problem is that the report itself is a Queue of images, whereas the T&C's are in PDF format. So whenever I do an "Enqueue", adding to the streams, it's looking at that PDF like one big image, as opposed to two pages. This causes a GDI+ generics error. Is there anyway for me to convert the PDF into the proper image format so that I can combine these documents? Here's the code I have so far:
internal static void DoPrintInvoice(int orderID, SalesOrderBLL.DocumentType doctype, string printer, int copies, List<string> lines)
{
using (var context = rempscoDataContext.CreateReadOnlyContext())
using (MiniProfiler.Current.Step("DoPrintInvoice()"))
{
//Customer Opt-Out
// Generate Report
using (var report = GetSalesOrderReport(orderID, _DocumentTypeDescriptions[doctype], doctype != DocumentType.InvoiceLetterhead, lines))
{
// returns queue of streams.
var streams = PrintingBLL.RenderStreams(report, landscape: false);
// returns byte array
var TermsAndConditions = GetTermsAndConditions();
//convert byte array to memory stream.
var TCStream = new MemoryStream(TermsAndConditions);
//conditional to add T&C's to stream.
if (doctype == DocumentType.OrderAcknowledgement)
{
streams.Enqueue(TCStream);
}
ParallelInvoke(
() => SaveSalesOrderPDF(orderID, doctype, report),
() => PrintingBLL.PrintStreams(streams, string.Format("Sales Order ({0})", report.DisplayName), printer, copies, false)
);
}
}
}
I've tried to convert the terms and conditions into an image, and back to a byte array but it gives me the same GDI generic issue. Any help would be greatly appreciated!
Have you looked at PDFSharp? I have had good luck working with it in the past for rendering PDFs.
www.pdfsharp.com
I need to merge N PDF files into one. I create a blank file first
byte[] pdfBytes = null;
var ms = new MemoryStream();
var doc = new iTextSharp.text.Document();
var cWriter = new PdfCopy(doc, ms);
Later I cycle through html strings array
foreach (NBElement htmlString in someElement.Children())
{
byte[] msTempDoc = getPdfDocFrom(htmlString.GetString(), cssString.GetString());
addPagesToPdf(cWriter, msTempDoc);
}
In getPdfDocFrom I create pdf file using XMLWorkerHelper and return it as byte array
private byte[] getPdfDocFrom(string htmlString, string cssString)
{
var tempMs = new MemoryStream();
byte[] tempMsBytes;
var tempDoc = new iTextSharp.text.Document();
var tempWriter = PdfWriter.GetInstance(tempDoc, tempMs);
tempDoc.Open();
using (var msCss = new MemoryStream(System.Text.Encoding.UTF8.GetBytes(cssString)))
{
using (var msHtml = new MemoryStream(System.Text.Encoding.UTF8.GetBytes(htmlString)))
{
//Parse the HTML
iTextSharp.tool.xml.XMLWorkerHelper.GetInstance().ParseXHtml(tempWriter, tempDoc, msHtml, msCss);
tempMsBytes = tempMs.ToArray();
}
}
tempDoc.Close();
return tempMsBytes;
}
Later on I try to add pages from this PDF file to the blank one.
private static void addPagesToPdf(PdfCopy mainDocWriter, byte[] sourceDocBytes)
{
using (var msOut = new MemoryStream())
{
PdfReader reader = new PdfReader(new MemoryStream(sourceDocBytes));
int n = reader.NumberOfPages;
PdfImportedPage page;
for (int i = 1; i <= n; i++)
{
page = mainDocWriter.GetImportedPage(reader, i);
mainDocWriter.AddPage(page);
}
}}
It breaks when it tries to create a PdfReader from the byte array I pass to the function. "Rebuild failed: trailer not found.; Original message: PDF startxref not found."
I used another library to work with PDF before. I passed 2 PdfDocuments as an objects and just added pages from one to another in cycle. It didn't support Css though, so I had to switch to ITextSharp.
I don't quite get the difference between PdfWriter and PdfCopy.
There a logical error in your code. When you create a document from scratch as is done in the getPdfDocFrom() method, the document isn't complete until you've triggered the Close() method. In this Close() method, a trailer is created as well as a cross-reference (xref) table. The error tells you that those are missing.
Indeed, you do call the Close() method:
tempDoc.Close();
But by the time you Close() the document, it's too late: you have already created the tempMsBytes array. You need to create that array after you close the document.
Edit: I don't know anything about C#, but if MemoryStream clears its buffer after closing it, you could use mainDocWriter.CloseStream = false; so that the MemoryStream isn't closed when you close the document.
In Java, it would be a bad idea to set the "close stream" parameter to false. When I read the answers to the question Create PDF in memory instead of physical file I see that C# probably doesn't always require this extra line.
Remark: merging files by adding PdfImportedPage instances to a PdfWriter is an example of bad taste. If you are using iTextSharp 5 or earlier, you should use PdfCopy or PdfSmartCopy to do that. If you use PdfWriter, you throw away a lot of information (e.g. link annotations).
I am trying to manipulate a PDF, it functions as a template. What I am trying is replacing 'placeholders' in the PDF template with my data. So someone makes a PDF template in Scribus for example, and adds an empty image with the name "company_logo". My application sees an image placeholder with the name "company_logo" and it adds the company logo there.
I can browse AcroFields with iTextSharp library and set text in a text field (for example) but AcroFields doesn't list the image placeholder. I've got the feeling that AcroFields is not what I am looking for.
So how can I get a list (or tree) of all objects from the PDF and read their properties (like position, size, contents, etc).
P.S. I do not necessarily need to use iTextSharp, any other PDF lib will do as well. Preferably free.
A little pseudo code to make myself more clear
var object = Pdf.GetObjectById("company_logo");
object.SetValue(myImage);
object.SetPosition(x, y);
From your pseudo-code example, we understand that you want to replace the stream of an object that contains an image. There are several examples on how to do this.
For instance, in the SpecialID example, we create a PDF where we mark a specific image with a special ID. In the ResizeImage example, we track that image based on that special ID and we replace the stream:
object = reader.getPdfObject(i);
if (object == null || !object.isStream())
continue;
stream = (PRStream)object;
if (value.equals(stream.get(key))) {
PdfImageObject image = new PdfImageObject(stream);
BufferedImage bi = image.getBufferedImage();
if (bi == null) continue;
int width = (int)(bi.getWidth() * FACTOR);
int height = (int)(bi.getHeight() * FACTOR);
BufferedImage img = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
AffineTransform at = AffineTransform.getScaleInstance(FACTOR, FACTOR);
Graphics2D g = img.createGraphics();
g.drawRenderedImage(bi, at);
ByteArrayOutputStream imgBytes = new ByteArrayOutputStream();
ImageIO.write(img, "JPG", imgBytes);
stream.clear();
stream.setData(imgBytes.toByteArray(), false, PRStream.NO_COMPRESSION);
stream.put(PdfName.TYPE, PdfName.XOBJECT);
stream.put(PdfName.SUBTYPE, PdfName.IMAGE);
stream.put(key, value);
stream.put(PdfName.FILTER, PdfName.DCTDECODE);
stream.put(PdfName.WIDTH, new PdfNumber(width));
stream.put(PdfName.HEIGHT, new PdfNumber(height));
stream.put(PdfName.BITSPERCOMPONENT, new PdfNumber(8));
stream.put(PdfName.COLORSPACE, PdfName.DEVICERGB);
}
You will find another example in the book The Best iText Questions on StackOverflow where I answered the following question: PDF Convert to Black And White PNGs
I wrote the ReplaceImage example to show how to replace the image:
public static void replaceStream(PRStream orig, PdfStream stream) throws IOException {
orig.clear();
ByteArrayOutputStream baos = new ByteArrayOutputStream();
stream.writeContent(baos);
orig.setData(baos.toByteArray(), false);
for (PdfName name : stream.getKeys()) {
orig.put(name, stream.get(name));
}
}
As you can see, it isn't as trivial as saying:
var object = Pdf.GetObjectById("company_logo");
object.SetValue(myImage);
As I explained in my comment, this doesn't make sense:
object.SetPosition(x, y);
The objects we're manipulating are streams that are used as Image XObjects. The advantage of having Image XObjects is that they can be reused. For instance: if you have the same logo on every page, then you want to store the bytes of that image only once and reuse the same logo multiple times. This means that the object with the image bytes doesn't know anything about its position. The position is determined in the content stream. It depends on the CTM.
Did you have a look at the scribus scripting capabilities?
Since you create a tamplate in scribus You could also write a short python script which replaces your placeholders with your final data and exports the final PDF.
Since scribus 1.5 it is also possible to call the python scripts from the commandline.
my target is to open an existing pdf, add or remove some pages while preserving the metadata (Author, Subject, ...) in a Windows.Forms C# application.
I use iTextSharp and found examples how to add or remove pages by using the PdfConcatenate class. To keep the metadata I use a PdfStamper afterwards. To speed things up I want to do the modifications in memory before storing the result to disk.
The problem is NOT adding or removing the pages but to keep the metadata in the same step.
So can anybody tell me/giva an example on how to achieve this (better) or am I on the completely wrong track?
Here my current code (see comments for problem related lines):
public void RemovePagesInFile(string documentLocation, int pageIndexFrom, int pageCount)
{
// TB: open the pdf
using (PdfReader sourcePdfReader = new PdfReader(documentLocation))
using (MemoryStream concatenatedTargetStream = new MemoryStream((int)sourcePdfReader.FileLength))
{
// TB: use a concatenator to create a new pdf containing only the desired pages
PdfConcatenate concatenator = new PdfConcatenate(concatenatedTargetStream);
// TB: create a list with the page numbers to keep
List<int> pagesToKeep = new List<int>();
for (int i = 1; i <= pageIndexFrom; i++)
{
pagesToKeep.Add(i);
}
for (int i = pageIndexFrom + pageCount + 1; i <= sourcePdfReader.NumberOfPages; i++)
{
pagesToKeep.Add(i);
}
// TB: execute the page copy
sourcePdfReader.SelectPages(pagesToKeep);
concatenator.AddPages(sourcePdfReader);
// TB: problem(s) here:
// 1. when calling concatenator.Close() the memory stream gets disposed as expected.
// concatenator.Close();
// 2. even when calling concatenator.WriterFlush() the memory stream seems to be missing content (error when creating targetReader (see below)).
// concatenator.Writer.Flush();
// 3. when keeping concatenator open the same error as above occures (I assume not all bytes have been written to the memory stream)
// TB: preserve the meta data from the source document
// => ERROR here: "Rebuild trailer not found. Original Error: PDF startxref not found"
using (PdfReader targetReader = new PdfReader(concatenatedTargetStream))
using (MemoryStream targetStream = new MemoryStream((int)concatenatedTargetStream.Length))
{
using (PdfStamper stamper = new PdfStamper(targetReader, targetStream))
{
stamper.MoreInfo = sourcePdfReader.Info;
// TB: same problem as above with stamper ?
stamper.Close();
}
// TB: close the reader to be able to access the source pdf
sourcePdfReader.Close();
// TB: write the modified pdf to the disk
File.WriteAllBytes(documentLocation, targetStream.ToArray());
}
}
}
Two changes need to be made. Call
concatenator.Writer.CloseStream = false
before calling
concatenator.Close()
Do the same thing for the PdfStamper and you're set.
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I am currently trying to recompress a pdf that has already been created, I am trying to find a way to recompress the images that are in the document, to reduce the file size.
I have been trying to do this with the DataLogics PDE and iTextSharp libraries but I can not find a way to do the stream recompression of the items.
I have though about looping over the xobjects and getting the images and then dropping the DPI down to 96 or using the libjpeg C# implimentation to change the quality of the image but getting it back into the pdf stream seems to always end up, with memory corruption or some other issue.
Any samples will be appreciated.
Thanks
iText and iTextSharp have some methods for replacing indirect objects. Specifically there's PdfReader.KillIndirect() which does what it says and PdfWriter.AddDirectImageSimple(iTextSharp.text.Image, PRIndirectReference) which you can then use to replace what you killed off.
In pseudo C# code you'd do:
var oldImage = PdfReader.GetPdfObject();
var newImage = YourImageCompressionFunction(oldImage);
PdfReader.KillIndirect(oldImage);
yourPdfWriter.AddDirectImageSimple(newImage, (PRIndirectReference)oldImage);
Converting the raw bytes to a .Net image can be tricky, I'll leave that up to you or you can search here. Mark has a good description here. Also, technically PDFs don't have a concept of DPI, that's for printers mostly. See the answer here for more on that.
Using the method above your compression algorithm can actually do two things, physically shrink the image as well as apply JPEG compression. When you physically shrink the image and add it back it will occupy the same amount of space as the original image but with less pixels to work with. This will get you what you consider to be DPI reduction. The JPEG compression speaks for itself.
Below is a full working C# 2010 WinForms app targeting iTextSharp 5.1.1.0. It takes an existing JPEG on your desktop called "LargeImage.jpg" and creates a new PDF from it. Then it opens the PDF, extracts the image, physically shrinks it to 90% of the original size, applies 85% JPEG compression and writes it back to the PDF. See the comments in the code for more of an explanation. The code needs lots more null/error checking. Also looks for NOTE comments where you'll need to expand to handle other situations.
using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.Drawing.Drawing2D;
using System.Windows.Forms;
using System.IO;
using iTextSharp.text;
using iTextSharp.text.pdf;
namespace WindowsFormsApplication1 {
public partial class Form1 : Form {
public Form1() {
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e) {
//Our working folder
string workingFolder = Environment.GetFolderPath(Environment.SpecialFolder.Desktop);
//Large image to add to sample PDF
string largeImage = Path.Combine(workingFolder, "LargeImage.jpg");
//Name of large PDF to create
string largePDF = Path.Combine(workingFolder, "Large.pdf");
//Name of compressed PDF to create
string smallPDF = Path.Combine(workingFolder, "Small.pdf");
//Create a sample PDF containing our large image, for demo purposes only, nothing special here
using (FileStream fs = new FileStream(largePDF, FileMode.Create, FileAccess.Write, FileShare.None)) {
using (Document doc = new Document()) {
using (PdfWriter writer = PdfWriter.GetInstance(doc, fs)) {
doc.Open();
iTextSharp.text.Image importImage = iTextSharp.text.Image.GetInstance(largeImage);
doc.SetPageSize(new iTextSharp.text.Rectangle(0, 0, importImage.Width, importImage.Height));
doc.SetMargins(0, 0, 0, 0);
doc.NewPage();
doc.Add(importImage);
doc.Close();
}
}
}
//Now we're going to open the above PDF and compress things
//Bind a reader to our large PDF
PdfReader reader = new PdfReader(largePDF);
//Create our output PDF
using (FileStream fs = new FileStream(smallPDF, FileMode.Create, FileAccess.Write, FileShare.None)) {
//Bind a stamper to the file and our reader
using (PdfStamper stamper = new PdfStamper(reader, fs)) {
//NOTE: This code only deals with page 1, you'd want to loop more for your code
//Get page 1
PdfDictionary page = reader.GetPageN(1);
//Get the xobject structure
PdfDictionary resources = (PdfDictionary)PdfReader.GetPdfObject(page.Get(PdfName.RESOURCES));
PdfDictionary xobject = (PdfDictionary)PdfReader.GetPdfObject(resources.Get(PdfName.XOBJECT));
if (xobject != null) {
PdfObject obj;
//Loop through each key
foreach (PdfName name in xobject.Keys) {
obj = xobject.Get(name);
if (obj.IsIndirect()) {
//Get the current key as a PDF object
PdfDictionary imgObject = (PdfDictionary)PdfReader.GetPdfObject(obj);
//See if its an image
if (imgObject.Get(PdfName.SUBTYPE).Equals(PdfName.IMAGE)) {
//NOTE: There's a bunch of different types of filters, I'm only handing the simplest one here which is basically raw JPG, you'll have to research others
if (imgObject.Get(PdfName.FILTER).Equals(PdfName.DCTDECODE)) {
//Get the raw bytes of the current image
byte[] oldBytes = PdfReader.GetStreamBytesRaw((PRStream)imgObject);
//Will hold bytes of the compressed image later
byte[] newBytes;
//Wrap a stream around our original image
using (MemoryStream sourceMS = new MemoryStream(oldBytes)) {
//Convert the bytes into a .Net image
using (System.Drawing.Image oldImage = Bitmap.FromStream(sourceMS)) {
//Shrink the image to 90% of the original
using (System.Drawing.Image newImage = ShrinkImage(oldImage, 0.9f)) {
//Convert the image to bytes using JPG at 85%
newBytes = ConvertImageToBytes(newImage, 85);
}
}
}
//Create a new iTextSharp image from our bytes
iTextSharp.text.Image compressedImage = iTextSharp.text.Image.GetInstance(newBytes);
//Kill off the old image
PdfReader.KillIndirect(obj);
//Add our image in its place
stamper.Writer.AddDirectImageSimple(compressedImage, (PRIndirectReference)obj);
}
}
}
}
}
}
}
this.Close();
}
//Standard image save code from MSDN, returns a byte array
private static byte[] ConvertImageToBytes(System.Drawing.Image image, long compressionLevel) {
if (compressionLevel < 0) {
compressionLevel = 0;
} else if (compressionLevel > 100) {
compressionLevel = 100;
}
ImageCodecInfo jgpEncoder = GetEncoder(ImageFormat.Jpeg);
System.Drawing.Imaging.Encoder myEncoder = System.Drawing.Imaging.Encoder.Quality;
EncoderParameters myEncoderParameters = new EncoderParameters(1);
EncoderParameter myEncoderParameter = new EncoderParameter(myEncoder, compressionLevel);
myEncoderParameters.Param[0] = myEncoderParameter;
using (MemoryStream ms = new MemoryStream()) {
image.Save(ms, jgpEncoder, myEncoderParameters);
return ms.ToArray();
}
}
//standard code from MSDN
private static ImageCodecInfo GetEncoder(ImageFormat format) {
ImageCodecInfo[] codecs = ImageCodecInfo.GetImageDecoders();
foreach (ImageCodecInfo codec in codecs) {
if (codec.FormatID == format.Guid) {
return codec;
}
}
return null;
}
//Standard high quality thumbnail generation from http://weblogs.asp.net/gunnarpeipman/archive/2009/04/02/resizing-images-without-loss-of-quality.aspx
private static System.Drawing.Image ShrinkImage(System.Drawing.Image sourceImage, float scaleFactor) {
int newWidth = Convert.ToInt32(sourceImage.Width * scaleFactor);
int newHeight = Convert.ToInt32(sourceImage.Height * scaleFactor);
var thumbnailBitmap = new Bitmap(newWidth, newHeight);
using (Graphics g = Graphics.FromImage(thumbnailBitmap)) {
g.CompositingQuality = CompositingQuality.HighQuality;
g.SmoothingMode = SmoothingMode.HighQuality;
g.InterpolationMode = InterpolationMode.HighQualityBicubic;
System.Drawing.Rectangle imageRectangle = new System.Drawing.Rectangle(0, 0, newWidth, newHeight);
g.DrawImage(sourceImage, imageRectangle);
}
return thumbnailBitmap;
}
}
}
I don't know about iTextSharp, but you have to rewrite a PDF file if anything is changed, as it contains an xref table (index) with the exact file position of each object. This means if even one byte is added or removed, the PDF becomes corrupted.
Your best bet for recompressing the images is JBIG2 if they are B&W, or JPEG2000 otherwise, for which Jasper library will happily encode JPEG2000 codestreams for placement into PDF files at whatever quality you so desire.
If it were me I'd do it all from code without the PDF libraries. Just find all images (anything between stream and endstream after an occurance of JPXDecode (JPEG2000), JBIG2Decode (JBIG2) or DCTDecode (JPEG)) pull that out, reencode it with Jasper, then stick it back in again and update the xref table.
To update the xref table, find the positions of each object (starting 00001 0 obj) and just update the new positions in the xref table. It's not too much work, less than it sounds. You might be able to get all the offsets with a single regular expression (I'm not a C# programmer, but in PHP it would be that simple.)
Then finally update the value of the startxref tag in the trailer with the offset of the beginning of the xref table (where it says xref in the file).
Otherwise you'll end up decoding the entire PDF and rewriting it all, which will be slow, and you might lose something along the way.
There is an example on how to find and replace images in an existing PDF by the creator of iText. It's actually a small excerpt from his book. Since it's in Java, here's a simple replacement:
public void ReduceResolution(PdfReader reader, long quality) {
int n = reader.XrefSize;
for (int i = 0; i < n; i++) {
PdfObject obj = reader.GetPdfObject(i);
if (obj == null || !obj.IsStream()) {continue;}
PdfDictionary dict = (PdfDictionary)PdfReader.GetPdfObject(obj);
PdfName subType = (PdfName)PdfReader.GetPdfObject(
dict.Get(PdfName.SUBTYPE)
);
if (!PdfName.IMAGE.Equals(subType)) {continue;}
PRStream stream = (PRStream )obj;
try {
PdfImageObject image = new PdfImageObject(stream);
PdfName filter = (PdfName) image.Get(PdfName.FILTER);
if (
PdfName.JBIG2DECODE.Equals(filter)
|| PdfName.JPXDECODE.Equals(filter)
|| PdfName.CCITTFAXDECODE.Equals(filter)
|| PdfName.FLATEDECODE.Equals(filter)
) continue;
System.Drawing.Image img = image.GetDrawingImage();
if (img == null) continue;
var ll = image.GetImageBytesType();
int width = img.Width;
int height = img.Height;
using (System.Drawing.Bitmap dotnetImg =
new System.Drawing.Bitmap(img))
{
// set codec to jpeg type => jpeg index codec is "1"
System.Drawing.Imaging.ImageCodecInfo codec =
System.Drawing.Imaging.ImageCodecInfo.GetImageEncoders()[1];
// set parameters for image quality
System.Drawing.Imaging.EncoderParameters eParams =
new System.Drawing.Imaging.EncoderParameters(1);
eParams.Param[0] =
new System.Drawing.Imaging.EncoderParameter(
System.Drawing.Imaging.Encoder.Quality, quality
);
using (MemoryStream msImg = new MemoryStream()) {
dotnetImg.Save(msImg, codec, eParams);
msImg.Position = 0;
stream.SetData(msImg.ToArray());
stream.SetData(
msImg.ToArray(), false, PRStream.BEST_COMPRESSION
);
stream.Put(PdfName.TYPE, PdfName.XOBJECT);
stream.Put(PdfName.SUBTYPE, PdfName.IMAGE);
stream.Put(PdfName.FILTER, filter);
stream.Put(PdfName.FILTER, PdfName.DCTDECODE);
stream.Put(PdfName.WIDTH, new PdfNumber(width));
stream.Put(PdfName.HEIGHT, new PdfNumber(height));
stream.Put(PdfName.BITSPERCOMPONENT, new PdfNumber(8));
stream.Put(PdfName.COLORSPACE, PdfName.DEVICERGB);
}
}
}
catch {
// throw;
// iText[Sharp] can't handle all image types...
}
finally {
// may or may not help
reader.RemoveUnusedObjects();
}
}
}
You'll notice it's only handling JPEG. The logic is reversed (instead of explicitly handling only DCTDECODE/JPEG) so you can uncomment some of the ignored image types and experiment with the PdfImageObject in the code above. In particular, most of the FLATEDECODE images (.bmp, .png, and .gif) are represented as PNG (confirmed in the DecodeImageBytes method of the PdfImageObject source code). As far as I know, .NET does not support PNG encoding. There are some references to support this here and here. You can try a stand-alone PNG optimization executable, but you also have to figure out how to set PdfName.BITSPERCOMPONENT and PdfName.COLORSPACE in the PRStream.
For completeness sake, since your question specifically asks about PDF compression, here's how you compress a PDF with iTextSharp:
PdfStamper stamper = new PdfStamper(
reader, YOUR-STREAM, PdfWriter.VERSION_1_5
);
stamper.Writer.CompressionLevel = 9;
int total = reader.NumberOfPages + 1;
for (int i = 1; i < total; i++) {
reader.SetPageContent(i, reader.GetPageContent(i));
}
stamper.SetFullCompression();
stamper.Close();
You might also try and run the PDF through PdfSmartCopy to get the file size down. It removes redundant resources, but like the call to RemoveUnusedObjects() in the finally block, it may or may not help. That will depend on how the PDF was created.
IIRC iText[Sharp] doesn't deal well with JBIG2DECODE, so #Alasdair's suggestion looks good - if you want to take the time learning the Jasper library and using the brute-force approach.
Good luck.
EDIT - 2012-08-17, comment by #Craig:
To save the PDF after compressing the jpegs using the ReduceResolution() method above:
a. Instantiate a PdfReader object:
PdfReader reader = new PdfReader(pdf);
b. Pass the PdfReader to the ReduceResolution() method above.
c. Pass the altered PdfReader to a PdfStamper. Here's one way using a MemoryStream:
// Save altered PDF. then you can pass the btye array to a database, etc
using (MemoryStream ms = new MemoryStream()) {
using (PdfStamper stamper = new PdfStamper(reader, ms)) {
}
return ms.ToArray();
}
Or you can use any other Stream if you don't need to keep the PDF in memory. E.g. use a FileStream and save directly to disk.
I've written a library to do just that. It will also OCR the pdf's using Tesseract or Cuneiform and create searchable, compressed PDF files. It's a library that uses several open source projects (iTextsharp, jbig2 encoder, Aforge, muPDF#) to complete the task. You can check it out here http://hocrtopdf.codeplex.com/
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.
A simple way to compress PDF is using gsdll32.dll (Ghostscript) and Cyotek.GhostScript.dll (wrapper):
public static void CompressPDF(string sInFile, string sOutFile, int iResolution)
{
string[] arg = new string[]
{
"-sDEVICE=pdfwrite",
"-dNOPAUSE",
"-dSAFER",
"-dBATCH",
"-dCompatibilityLevel=1.5",
"-dDownsampleColorImages=true",
"-dDownsampleGrayImages=true",
"-dDownsampleMonoImages=true",
"-sPAPERSIZE=a4",
"-dPDFFitPage",
"-dDOINTERPOLATE",
"-dColorImageDownsampleThreshold=1.0",
"-dGrayImageDownsampleThreshold=1.0",
"-dMonoImageDownsampleThreshold=1.0",
"-dColorImageResolution=" + iResolution.ToString(),
"-dGrayImageResolution=" + iResolution.ToString(),
"-dMonoImageResolution=" + iResolution.ToString(),
"-sOutputFile=" + sOutFile,
sInFile
};
using(GhostScriptAPI api = new GhostScriptAPI())
{
api.Execute(arg);
}
}