How to read and write PDF files in Kotlin

How to read and write PDF files in Kotlin.

Here's a step-by-step tutorial on how to read and write PDF files in Kotlin.

Table of Contents

1. Introduction
2. Reading PDF Files
   • Importing the Required Libraries
   • Loading a PDF Document
   • Extracting Text from PDF
3. Writing PDF Files
   • Creating a New Document
   • Adding Content to the Document
   • Saving the Document
4. Conclusion

1. Introduction

PDF (Portable Document Format) is a popular file format used for document exchange. In Kotlin, we can read and write PDF files using external libraries like iText and PDFBox. In this tutorial, we will explore how to perform these operations using iText library.

2. Reading PDF Files

Importing the Required Libraries

To get started, we need to include the iText library in our project. Add the following dependency to your build.gradle file:

dependencies {
    implementation 'com.itextpdf:itextpdf:5.5.13'
}

Loading a PDF Document

To read a PDF file, we first need to load the document using the PdfReader class. Here's an example:

import com.itextpdf.text.pdf.PdfReader

fun main() {
    val reader = PdfReader("path/to/your/pdf/file.pdf")
    // Rest of your code
    reader.close()
}

Replace "path/to/your/pdf/file.pdf" with the actual path to your PDF file.

Extracting Text from PDF

Once the PDF document is loaded, we can extract text from it using the PdfReader class. Here's an example:

import com.itextpdf.text.pdf.PdfReader
import com.itextpdf.text.pdf.parser.PdfTextExtractor

fun main() {
    val reader = PdfReader("path/to/your/pdf/file.pdf")
    val numPages = reader.numberOfPages

    for (i in 1..numPages) {
        val text = PdfTextExtractor.getTextFromPage(reader, i)
        println("Page $i: $text")
    }

    reader.close()
}

This code will extract text from each page of the PDF document and print it to the console.

3. Writing PDF Files

Creating a New Document

To create a new PDF document, we need to use the Document class from the iText library. Here's an example:

import com.itextpdf.text.Document
import com.itextpdf.text.Paragraph
import com.itextpdf.text.pdf.PdfWriter

fun main() {
    val document = Document()
    PdfWriter.getInstance(document, FileOutputStream("path/to/your/pdf/file.pdf"))
    document.open()
    // Rest of your code
    document.close()
}

Replace "path/to/your/pdf/file.pdf" with the desired path and filename for your PDF file.

Adding Content to the Document

Once the document is created, we can add content to it using the Paragraph class. Here's an example:

import com.itextpdf.text.Document
import com.itextpdf.text.Paragraph
import com.itextpdf.text.pdf.PdfWriter

fun main() {
    val document = Document()
    PdfWriter.getInstance(document, FileOutputStream("path/to/your/pdf/file.pdf"))
    document.open()

    val paragraph = Paragraph("Hello, World!")
    document.add(paragraph)

    document.close()
}

This code will create a new PDF document and add a "Hello, World!" paragraph to it.

Saving the Document

Finally, we need to save the document using the PdfWriter class. Here's an example:

import com.itextpdf.text.Document
import com.itextpdf.text.Paragraph
import com.itextpdf.text.pdf.PdfWriter

fun main() {
    val document = Document()
    val writer = PdfWriter.getInstance(document, FileOutputStream("path/to/your/pdf/file.pdf"))
    document.open()

    val paragraph = Paragraph("Hello, World!")
    document.add(paragraph)

    document.close()
    writer.close()
}

Make sure to call the close() method on both the Document and PdfWriter instances to save and close the PDF file properly.

4. Conclusion

In this tutorial, we learned how to read and write PDF files in Kotlin using the iText library. We explored how to load a PDF document, extract text from it, create a new document, add content to it, and save the document. With these techniques, you can now manipulate PDF files in your Kotlin applications.