iText7 pdf to blob c#

Question

使用c#和iText7，我需要修改现有的PDF并将其保存到blob存储。我有一个控制台应用程序，它正是我需要使用文件系统:

PdfReader reader = new PdfReader(source);
PdfWriter writer = new PdfWriter(destination2);
PdfDocument pdfDoc = new PdfDocument(reader, writer);
PdfAcroForm form = PdfAcroForm.GetAcroForm(pdfDoc, true);
fields = form.GetFormFields();
fields.TryGetValue("header", out PdfFormField cl);
var type = cl.GetType();
cl.SetValue("This is a header");
pdfDoc.Close();

这很好。然而，我不知道如何做同样的事情从blob存储中提取PDF并将新的PDF发送到blob存储

IDictionary<string, PdfFormField> fields;
MemoryStream outStream = new MemoryStream();
var pdfTemplate = _blobStorageService.GetBlob("mycontainer", "TestPDF.pdf");
PdfReader reader = new PdfReader(pdfTemplate);
PdfWriter writer = new PdfWriter(outStream);
PdfDocument pdfDoc = new PdfDocument(reader, writer);
PdfAcroForm form = PdfAcroForm.GetAcroForm(pdfDoc, true);
fields = form.GetFormFields();
fields.TryGetValue("header", out PdfFormField cl);
cl.SetValue("This is a header");
pdfDoc.Close();
outStream.Position = 0;
_blobStorageService.UploadBlobAsync("mycontainer", **THIS IS THE ISSUE**, "newpdf.pdf");

我想我需要得到pdfDoc作为一个字节数组。Outstream是不正确的，它的长度只有15

Answer 1

下面的代码展示了如何将PDF从文件读取为字节[]，以及如何修改存储为字节[]的PDF。

下载并安装NuGet包:iText7

• 在解决方案资源管理器中，右键单击<项目名称>选择Manage NuGet Packages…
• 点击浏览
• 在搜索框中输入:iText7
• 选择iText7
• 选择所需版本
• 点击

添加以下using语句:

using System.IO;
using iText.Kernel.Pdf;
using iText.Forms;
using iText.Forms.Fields;

Get PDF as byte[](GetPdfBytes):

public static Task<byte[]> GetPdfBytes(string pdfFilename)
{
byte[] pdfBytes = null;
using (PdfReader reader = new PdfReader(pdfFilename))
{
using (MemoryStream msPdfWriter = new MemoryStream())
{
using (PdfWriter writer = new PdfWriter(msPdfWriter))
{
using (PdfDocument pdfDoc = new PdfDocument(reader, writer))
{
//don't close underlying streams when PdfDocument is closed
pdfDoc.SetCloseReader(false);
pdfDoc.SetCloseWriter(false);
//close
pdfDoc.Close();
//set value
msPdfWriter.Position = 0;
//convert to byte[]
pdfBytes = msPdfWriter.ToArray();
}
}
}
}
return Task.FromResult(pdfBytes);
}

使用:

byte[] pdfBytes = null;
string filename = string.Empty;
OpenFileDialog ofd = new OpenFileDialog();
ofd.Filter = "PDF File (*.pdf)|*.pdf";
if (ofd.ShowDialog() == DialogResult.OK)
{
//get PDF as byte[]
var tResult = GetPdfBytes(ofd.FileName);
pdfBytes = tResult.Result;
//For testing, write back to file so we can ensure that the PDF file opens properly
//create a new filename
filename = System.IO.Path.GetFileNameWithoutExtension(ofd.FileName) + " - Test.pdf";
filename = System.IO.Path.Combine(System.IO.Path.GetDirectoryName(ofd.FileName), filename);
//save to file
File.WriteAllBytes(filename, pdfBytes);
System.Diagnostics.Debug.WriteLine("Saved as '" + filename + "'");
}

修改存储在字节中的PDF [](ModifyPdf)

public static Task<byte[]> ModifyPdf(byte[] pdfBytes)
{
byte[] modifiedPdfBytes = null;
using (MemoryStream ms = new MemoryStream(pdfBytes))
{
using (PdfReader reader = new PdfReader(ms))
{
using (MemoryStream msPdfWriter = new MemoryStream())
{
using (PdfWriter writer = new PdfWriter(msPdfWriter))
{
using (PdfDocument pdfDoc = new PdfDocument(reader, writer))
{
//don't close underlying streams when PdfDocument is closed
pdfDoc.SetCloseReader(false);
pdfDoc.SetCloseWriter(false);
//get AcroForm from document
PdfAcroForm form = PdfAcroForm.GetAcroForm(pdfDoc, true);
//get form fields
IDictionary<string, PdfFormField> fields = form.GetFormFields();
//for testing, show all fields
foreach (KeyValuePair<string, PdfFormField> kvp in fields)
{
System.Diagnostics.Debug.WriteLine("Key: '" + kvp.Key + "' Value: '" + kvp.Value + "'");
}
PdfFormField cl = null;
//get specified field
fields.TryGetValue("1 Employee name", out cl);
//set value for specified field
cl.SetValue("John Doe");
//close PdfDocument
pdfDoc.Close();
//set value
msPdfWriter.Position = 0;
//convert to byte[]
modifiedPdfBytes = msPdfWriter.ToArray();
}
}
}
}
}
return Task.FromResult(modifiedPdfBytes);
}

使用:

byte[] pdfBytes = null;
string filename = string.Empty;
OpenFileDialog ofd = new OpenFileDialog();
ofd.Filter = "PDF File (*.pdf)|*.pdf";
if (ofd.ShowDialog() == DialogResult.OK)
{
//get PDF as byte[]
var tResult = GetPdfBytes(ofd.FileName);
pdfBytes = tResult.Result;
//modify PDF
pdfBytes = await ModifyPdf(pdfBytes);
//create a new filename
filename = System.IO.Path.GetFileNameWithoutExtension(ofd.FileName) + " - TestModified.pdf";
filename = System.IO.Path.Combine(System.IO.Path.GetDirectoryName(ofd.FileName), filename);
//save to file
File.WriteAllBytes(filename, pdfBytes);
System.Diagnostics.Debug.WriteLine("Saved as '" + filename + "'");
}

---

下面的代码改编自Sample01b_HelloWorldAsync.cs，未经测试。

下载并安装NuGet包:Azure.Storage.Blobs

添加以下using语句:

using Azure.Storage.Blobs;

DownloadPdf:

public static async Task<byte[]> DownloadPdf(string connectionString, string blobContainerName, string blobName)
{
byte[] pdfBytes = null;

using (MemoryStream ms = new MemoryStream())
{
// Get a reference to the container and then create it
BlobContainerClient container = new BlobContainerClient(connectionString, blobContainerName);
Azure.Response<Azure.Storage.Blobs.Models.BlobContainerInfo> responseCA = await container.CreateAsync();
// Get a reference to the blob
BlobClient blob = container.GetBlobClient(blobName);
// Download the blob's contents and save it to a file
Azure.Response responseDTA = await blob.DownloadToAsync(ms);
//set value
ms.Position = 0;
//convert to byte[]
pdfBytes = ms.ToArray();
}
return pdfBytes;
}

UploadPdf:

public static async Task<Azure.Response<Azure.Storage.Blobs.Models.BlobContentInfo>> UpdloadPdf(byte[] pdfBytes, string connectionString, string blobContainerName, string blobName)
{
Azure.Response<Azure.Storage.Blobs.Models.BlobContentInfo> result = null;
using (MemoryStream ms = new MemoryStream(pdfBytes))
{
//this statement may not be necessary
ms.Position = 0; 
// Get a reference to the container and then create it
BlobContainerClient container = new BlobContainerClient(connectionString, blobContainerName);
await container.CreateAsync();
// Get a reference to the blob
BlobClient blob = container.GetBlobClient(blobName);
//upload
result = await blob.UploadAsync(ms);
}
return result;
}

这是一个PDF文件用于测试。