How to modify the content of pdf files in golang

In the computer field, PDF (Portable Document Format) is a very popular file format. Because it can be printed, shared and even edited, people use PDF documents in various situations. However, in some cases, we need to modify the PDF through code, such as adding headers and footers, modifying images, adding watermarks, etc. In this case, we need to use an efficient and easy-to-use programming language, and then Golang can become a more suitable solution.

Golang, also called Go, is a programming language developed by Google. Once it was launched, it was highly popular due to its concurrency support and simple and easy-to-learn syntax style. A large number of developers have begun to use it for programming tasks in various computer technology fields, including modifying PDFs using the Go language.

Before that, what needs to be made clear is that PDF files are a file type with a very complex format. Because it can contain basically any file type a user needs, they are arranged and displayed in different ways in the document. Unfortunately, Golang is not a standard library that can directly handle PDF, so a third-party library is needed to read, write and modify PDF files.

Several common third-party Golang libraries include:

1. gofpdf: Golang third-party library, used to generate PDF files.
2. gofpdi: Golang third-party library for reading and updating a single page of an existing PDF file.

Both libraries are completely free and can be installed through the npm command on the official website. Before starting to use it, you need to clarify what you need to do to modify the PDF. For example, if you need to add or To modify the text content of pdf, it is more appropriate to use gofpdf; if you need to make some modifications to an existing pdf file, such as adding watermarks, deleting forms, rotating pages, etc., using gofpdi is more suitable.

Below, we take gofpdi as an example and give a simple example of adding a "Watermark" watermark to an existing PDF:

First, we need to install the gofpdi library as follows :

go get github.com/phpdave11/gofpdi/v4

Then, we write the following code:

package main

import (
    "fmt"
    "github.com/phpdave11/gofpdi/v4"
)

func main() {
    // 打开一个PDF文件
    pdf := gofpdi.NewImporter()

    _, err := pdf.Import("test.pdf", "")
    if err != nil {
        fmt.Println("Error:", err)
        return
    }

    // 在PDF中添加一个“水印”
    pdf.AddWatermarkText("Watermark")

    // 保存新PDF文件
    err = pdf.OutputFileAndClose("test_new.pdf")
    if err != nil {
        fmt.Println("Error:", err)
        return
    }
}

At this point, we have successfully used Golang to add watermarks to PDF files. Such a simple code implementation is easy to understand and does not require tedious steps. Therefore, many developers are using Golang to modify PDF files efficiently. Of course, the premise is that you need to understand the structure and content of the required PDF file and use a suitable third-party library to modify it.

In short, Golang is a particularly excellent programming language. Its concurrency features and standardized syntax make it more and more popular. For processing PDF files, especially for those who need to read and modify PDF files, it can save more time and workload. By becoming familiar with the Go programming language and using third-party libraries such as gofpdi, you can easily read, write and modify PDF files efficiently.

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