Java/Convert PDF to PNG Images

In certain cases, images are more flexible than PDF files and thus converting PDF to image is a common task that we may face in our daily work. This article will share how to programmatically convert PDF to images in Java application from the following two aspects.

• Convert a Whole PDF Document to Multiple Images
• Convert a Particular PDF Page to an Image

Installation

A free Java library is required to achieve this task, and there are 2 methods to install the product.
Method 1: Download the free library(Free Spire.PDF for Java) and unzip it. Then add the Spire.Pdf.jar file to your project as dependency.

Method 2: Directly add the jar dependency to maven project by adding the following configurations to the pom.xml.

<repositories>
    <repository>
        <id>com.e-iceblue</id>
        <name>e-iceblue</name>
        <url>https://repo.e-iceblue.com/nexus/content/groups/public/</url>
    </repository>
</repositories>
<dependencies>
    <dependency>
        <groupId>e-iceblue</groupId>
        <artifactId>spire.pdf.free</artifactId>
        <version>5.1.0</version>
    </dependency>
</dependencies>

A screenshot of the input PDF file containing 3 pages.

Free Spire.PDF for Java allows users to convert all pages or a specific page of a PDF file to images and set the image Dpi using PdfDocument.saveAsImage(int pageIndex, PdfImageType type, int dpiX, int dpiY) method.

Convert a Whole PDF Document to Multiple Images

import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import com.spire.pdf.PdfDocument;
import com.spire.pdf.graphics.PdfImageType;
import javax.imageio.ImageIO;

public class WholePDFToImages {
    public static void main(String[] args) throws IOException {
        //Create a PdfDocument instance
        PdfDocument pdf = new PdfDocument();

        //Load a PDF sample document
        pdf.loadFromFile("input.pdf");

        //Loop through every page
        for (int i = 0; i < pdf.getPages().getCount(); i++) {
            //Convert all pages to images and set the image Dpi
            BufferedImage image = pdf.saveAsImage(i, PdfImageType.Bitmap,500,500);
            //Save images to a specific folder as a .png files
            File file = new File("C:\\Users\\Administrator\\Desktop\\PDFToImages" + "/" + String.format(("ToImage-img-%d.png"), i));
            ImageIO.write(image, "PNG", file);
        }
        pdf.close();
    }
}

Convert a Particular PDF Page to an Image

import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import com.spire.pdf.PdfDocument;
import com.spire.pdf.graphics.PdfImageType;
import javax.imageio.ImageIO;

public class ParticularPDFToImage {
    public static void main(String[] args) throws IOException {
        //Create a PdfDocument instance
        PdfDocument pdf = new PdfDocument();

        //Load a PDF sample document
        pdf.loadFromFile("input.pdf");

        //Convert the third page to an image and set the image Dpi
        BufferedImage image= pdf.saveAsImage(2, PdfImageType.Bitmap,500,500);

        //Save the image to another file as a .png format 
        ImageIO.write(image, "PNG", new File("ToPNG.png"));
    }
}