How to Convert PNG to PDF in Java (Tutorial)

Prerequisites

To create a PNG to PDF conversion application, you will need the following prerequisites downloaded and installed:

1. Java Development Kit (JDK): The latest version of JDK must be installed on your computer to compile and run the convert PNG to PDF application. The JDK can be downloaded from the Oracle website.
2. Maven: Maven needs to be installed as it is a build automation tool used primarily for Java projects. Maven can be downloaded from the Apache Maven website.

3. IronPDF Java Library: Now you will need the latest version of IronPDF added as a dependency to your PNG to PDF conversion project. Add the following IronPDF dependency to your project's pom.xml file:

   <dependency>
     <groupId>com.ironsoftware</groupId>
     <artifactId>ironpdf-java</artifactId>
     <version>VERSION_NUMBER</version>
   </dependency>

   <dependency>
     <groupId>com.ironsoftware</groupId>
     <artifactId>ironpdf-java</artifactId>
     <version>VERSION_NUMBER</version>
   </dependency>

   XML

4. You will also need to add the Slf4j dependency in the pom.xml file.

   <dependency>
       <groupId>org.slf4j</groupId>
       <artifactId>slf4j-simple</artifactId>
       <version>2.0.5</version>
   </dependency>

   <dependency>
       <groupId>org.slf4j</groupId>
       <artifactId>slf4j-simple</artifactId>
       <version>2.0.5</version>
   </dependency>

   XML

Once all the prerequisites are downloaded and installed, the project can now be used to convert PNG images to PDF documents in Java applications.

Add Imports to Java Main File

First of all, you will need the following imports for converting PNG images to PDF files using IronPDF in your Java application.

import com.ironsoftware.ironpdf.PdfDocument;
import java.io.IOException;
import java.nio.file.*;
import java.util.ArrayList;
import java.util.List;

import com.ironsoftware.ironpdf.PdfDocument;
import java.io.IOException;
import java.nio.file.*;
import java.util.ArrayList;
import java.util.List;

Once the imports are added, you are good to go with the image-to-PDF conversion.

Convert Single PNG to PDF File

IronPDF helps developers convert a single PNG or JPG image to a PDF file with a few simple steps. The Java code snippet is shown in the following example:

// Create a list to hold the path of the image to be converted
List<Path> paths = new ArrayList<>();
paths.add(Paths.get("example.png")); // Add image path to the list

// Create a PDF document from the image and save the PDF
PdfDocument.fromImage(paths).saveAs(Paths.get("example.pdf"));

// Create a list to hold the path of the image to be converted
List<Path> paths = new ArrayList<>();
paths.add(Paths.get("example.png")); // Add image path to the list

// Create a PDF document from the image and save the PDF
PdfDocument.fromImage(paths).saveAs(Paths.get("example.pdf"));

Here, you first need to get the path of the image file that you are trying to convert to PDF. Then, you add that image path to a List and call the fromImage method. Finally, call the saveAs method to save the converted PNG file to the filesystem.

Convert Multiple PNGs into a PDF File

IronPDF also allows developers to combine multiple PNG or JPG images into a single PDF document, as shown in the following code example.

// Define the directory containing images to convert
Path imageDirectory = Paths.get("assets/images");

// Create an empty List to hold image Paths
List<Path> imageFiles = new ArrayList<>();

// Populate the List with images' paths from the directory using DirectoryStream
try (DirectoryStream<Path> stream = Files.newDirectoryStream(imageDirectory, "*.{png, jpg, gif}")) {
    for (Path entry : stream) {
        imageFiles.add(entry); // Add image file path to the list
    }

    // Create a PDF document from all images and save it
    PdfDocument.fromImage(imageFiles).saveAs(Paths.get("multiple_images.pdf"));
} catch (IOException exception) {
    throw new RuntimeException(String.format("Error converting images to PDF from directory: %s: %s",
            imageDirectory,
            exception.getMessage()),
            exception);
}

// Define the directory containing images to convert
Path imageDirectory = Paths.get("assets/images");

// Create an empty List to hold image Paths
List<Path> imageFiles = new ArrayList<>();

// Populate the List with images' paths from the directory using DirectoryStream
try (DirectoryStream<Path> stream = Files.newDirectoryStream(imageDirectory, "*.{png, jpg, gif}")) {
    for (Path entry : stream) {
        imageFiles.add(entry); // Add image file path to the list
    }

    // Create a PDF document from all images and save it
    PdfDocument.fromImage(imageFiles).saveAs(Paths.get("multiple_images.pdf"));
} catch (IOException exception) {
    throw new RuntimeException(String.format("Error converting images to PDF from directory: %s: %s",
            imageDirectory,
            exception.getMessage()),
            exception);
}

The fromImage method in the above code can also accept a list of PNG image path objects. Each path object references a valid path to an image stored locally. In this case, the images are from the same directory, so a DirectoryStream found in java.nio.file classes is used to build up a list of all the images contained in the directory.

Now, the fromImage method will render each PNG or JPG image present in the list on a separate page of the PDF document. Finally, use the saveAs method to save the converted images to the multiple_images.pdf output.

After running the project with any of the above code examples, the output is generated in PDF file format. Here, the output shown is from the "Convert PNG to PDF" Multiple Images.

PNG to PDF Output

You can check further code examples on image conversion with IronPDF and also download IronPDF for Java from the IronPDF Official Website.

IronPDF for Java

IronPDF has a great quality of rendering all images and text without losing any format. Form components in PDFs are also editable in the converted PDF file.