How to read PNG files in Java

In this article, I will show you how to read PNG files in Java. We also have a related article covering how to write PNG files in Java.

As part of a separate project to provide customers with a solution to provide an easy way to convert PDF to PNG files in our JPedal software, we wanted better PNG support than we could find in ImageIO and other image libraries. So we wrote our own implementation and made it available as part of JDeli.

What is a PNG?

PNG stands for Portable Network Graphics. It is a lossless, bitmap image format popular on the world wide web because it supports transparency in browsers. It was created to remove the need for GIF images in web browsers. Unlike GIF, PNG is an open standard with no patents.

The file name extension for PNG files is: .png

How to read a PNG image in Java with ImageIO

Step 1 Create a File handle, InputStream, or URL pointing to the raw PNG image.
Step 2 ImageIO will now be able to read a PNG file into a BufferedImage. This syntax is like so:

BufferedImage image = ImageIO.read(pngFileOrInputStreamOrURL)

How to read a PNG image in Java with JDeli

Step 1 Add JDeli to your class or module path. (download the trial jar).
Step 2 Create a File handle or InputStream pointing to the raw PNG image. You can also use a byte[] containing the image data.
Step 3 Read the PNG image into a BufferedImage

BufferedImage image = JDeli.read(pngFile);

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Start reading and writing images with one line of code

Read: BufferedImage image = JDeli.read(streamOrFile);

Write: JDeli.write(myBufferedImage, OutputFormat.HEIC, outputStreamOrFile)

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