使用iTextSharp的PDF文件中删除水印 [英] Removing Watermark from a PDF using iTextSharp
问题描述
我使用Pdfstamper添加上的PDF水印。这里是code：
I added a watermark on pdf using Pdfstamper. Here is the code:
for (int pageIndex = 1; pageIndex <= pageCount; pageIndex++)
{
iTextSharp.text.Rectangle pageRectangle = reader.GetPageSizeWithRotation(pageIndex);
PdfContentByte pdfData = stamper.GetUnderContent(pageIndex);
pdfData.SetFontAndSize(BaseFont.CreateFont(BaseFont.HELVETICA, BaseFont.CP1252,
BaseFont.NOT_EMBEDDED), watermarkFontSize);
PdfGState graphicsState = new PdfGState();
graphicsState.FillOpacity = watermarkFontOpacity;
pdfData.SetGState(graphicsState);
pdfData.SetColorFill(iTextSharp.text.BaseColor.BLACK);
pdfData.BeginText();
pdfData.ShowTextAligned(PdfContentByte.ALIGN_CENTER, "LipikaChatterjee",
pageRectangle.Width / 2, pageRectangle.Height / 2, watermarkRotation);
pdfData.EndText();
}
这工作正常。现在，我想从我的PDF删除此水印。我看着iTextSharp的，但没有能够得到任何帮助。我甚至尝试添加水印的层，然后删除该层，但无法从PDF中删除图层的内容。我看着iText的为层去除，发现一类OCGRemover，但我没能得到一个等价类中iTextSharp的。
This works fine. Now I want to remove this watermark from my pdf. I looked into iTextSharp but was not able to get any help. I even tried to add watermark as layer and then delete the layer but was not able to delete the content of layer from the pdf. I looked into iText for layer removal and found a class OCGRemover but I was not able to get an equivalent class in iTextsharp.
推荐答案
我打算给你根据语句的疑点利益我甚至尝试添加水印为层和假设你正在处理要创建，而不是试图unwatermark别人的内容的内容。
I'm going to give you the benefit of the doubt based on the statement "I even tried to add watermark as layer" and assume that you are working on content that you are creating and not trying to unwatermark someone else's content.
PDF文件使用可选内容组（OCG）来存储对象的层。如果添加水印文字的一层就可以很容易再删除它。
PDFs use Optional Content Groups (OCG) to store objects as layers. If you add your watermark text to a layer you can fairly easily remove it later.
在code以下是一个完整的工作C＃2010 WinForms应用程序针对iTextSharp的5.1.1.0。它使用code基于布鲁诺的原始的Java code在这里找到。在code为三个部分。第1节创建了一个样本PDF让我们一起工作。第2节从创建的第一个新的PDF和应用水印每一页上一个单独的层。第3节从创建第二个最终的PDF，但消除了与我们的水印文字层。见code注释的更多详细信息。
The code below is a full working C# 2010 WinForms app targeting iTextSharp 5.1.1.0. It uses code based on Bruno's original Java code found here. The code is in three sections. Section 1 creates a sample PDF for us to work with. Section 2 creates a new PDF from the first and applies a watermark to each page on a separate layer. Section 3 creates a final PDF from the second but removes the layer with our watermark text. See the code comments for additional details.
当你创建一个 PdfLayer 对象，你可以给它命名为PDF阅读器中出现。不幸的是，我不能找到一种方法来访问此名称，以便低于code查找层内的实际水印文本。如果不使用额外的PDF图层我会推荐的仅内容流中寻找 / OC ，不浪费时间寻找你的实际水印文本。如果你找到一种方法通过名称来寻找 / OC 组请让我kwow！
When you create a PdfLayer object you can assign it a name to appear within a PDF reader. Unfortunately I can't find a way to access this name so the code below looks for the actual watermark text within the layer. If you aren't using additional PDF layers I would recommend only looking for /OC within the content stream and not wasting time looking for your actual watermark text. If you find a way to look for /OC groups by name please let me kwow!
using System;
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) {
string workingFolder = Environment.GetFolderPath(Environment.SpecialFolder.Desktop);
string startFile = Path.Combine(workingFolder, "StartFile.pdf");
string watermarkedFile = Path.Combine(workingFolder, "Watermarked.pdf");
string unwatermarkedFile = Path.Combine(workingFolder, "Un-watermarked.pdf");
string watermarkText = "This is a test";
//SECTION 1
//Create a 5 page PDF, nothing special here
using (FileStream fs = new FileStream(startFile, FileMode.Create, FileAccess.Write, FileShare.None)) {
using (Document doc = new Document(PageSize.LETTER)) {
using (PdfWriter witier = PdfWriter.GetInstance(doc, fs)) {
doc.Open();
for (int i = 1; i <= 5; i++) {
doc.NewPage();
doc.Add(new Paragraph(String.Format("This is page {0}", i)));
}
doc.Close();
}
}
}
//SECTION 2
//Create our watermark on a separate layer. The only different here is that we are adding the watermark to a PdfLayer which is an OCG or Optional Content Group
PdfReader reader1 = new PdfReader(startFile);
using (FileStream fs = new FileStream(watermarkedFile, FileMode.Create, FileAccess.Write, FileShare.None)) {
using (PdfStamper stamper = new PdfStamper(reader1, fs)) {
int pageCount1 = reader1.NumberOfPages;
//Create a new layer
PdfLayer layer = new PdfLayer("WatermarkLayer", stamper.Writer);
for (int i = 1; i <= pageCount1; i++) {
iTextSharp.text.Rectangle rect = reader1.GetPageSize(i);
//Get the ContentByte object
PdfContentByte cb = stamper.GetUnderContent(i);
//Tell the CB that the next commands should be "bound" to this new layer
cb.BeginLayer(layer);
cb.SetFontAndSize(BaseFont.CreateFont(BaseFont.HELVETICA, BaseFont.CP1252, BaseFont.NOT_EMBEDDED), 50);
PdfGState gState = new PdfGState();
gState.FillOpacity = 0.25f;
cb.SetGState(gState);
cb.SetColorFill(BaseColor.BLACK);
cb.BeginText();
cb.ShowTextAligned(PdfContentByte.ALIGN_CENTER, watermarkText, rect.Width / 2, rect.Height / 2, 45f);
cb.EndText();
//"Close" the layer
cb.EndLayer();
}
}
}
//SECTION 3
//Remove the layer created above
//First we bind a reader to the watermarked file, then strip out a bunch of things, and finally use a simple stamper to write out the edited reader
PdfReader reader2 = new PdfReader(watermarkedFile);
//NOTE, This will destroy all layers in the document, only use if you don't have additional layers
//Remove the OCG group completely from the document.
//reader2.Catalog.Remove(PdfName.OCPROPERTIES);
//Clean up the reader, optional
reader2.RemoveUnusedObjects();
//Placeholder variables
PRStream stream;
String content;
PdfDictionary page;
PdfArray contentarray;
//Get the page count
int pageCount2 = reader2.NumberOfPages;
//Loop through each page
for (int i = 1; i <= pageCount2; i++) {
//Get the page
page = reader2.GetPageN(i);
//Get the raw content
contentarray = page.GetAsArray(PdfName.CONTENTS);
if (contentarray != null) {
//Loop through content
for (int j = 0; j < contentarray.Size; j++) {
//Get the raw byte stream
stream = (PRStream)contentarray.GetAsStream(j);
//Convert to a string. NOTE, you might need a different encoding here
content = System.Text.Encoding.ASCII.GetString(PdfReader.GetStreamBytes(stream));
//Look for the OCG token in the stream as well as our watermarked text
if (content.IndexOf("/OC") >= 0 && content.IndexOf(watermarkText) >= 0) {
//Remove it by giving it zero length and zero data
stream.Put(PdfName.LENGTH, new PdfNumber(0));
stream.SetData(new byte[0]);
}
}
}
}
//Write the content out
using (FileStream fs = new FileStream(unwatermarkedFile, FileMode.Create, FileAccess.Write, FileShare.None)) {
using (PdfStamper stamper = new PdfStamper(reader2, fs)) {
}
}
this.Close();
}
}
}
这篇关于使用iTextSharp的PDF文件中删除水印的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
