Mark Stephens Mark has been working with Java and PDF since 1999 and is a big NetBeans fan. He enjoys speaking at conferences. He has an MA in Medieval History and a passion for reading.

How to resize images in Java

1 min read

image formats java

In this article I will show you how to resize images in Java.

ImageIO allows reading and writing or images in Java and processing the image. I will also cover image resizing using our JDeli image library.

How to resize an image in ImageIO

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

BufferedImage image = ImageIO.read(bmpFileOrInputStreamOrURL)

Step 3 Create a second BufferedImage at the new size

final int w = image.getWidth();
final int h = image.getHeight();
BufferedImage scaledImage = new BufferedImage((w * 2),(h * 2), BufferedImage.TYPE_INT_ARGB);

Step 4 Create a transformation

final AffineTransform at = AffineTransform.getScaleInstance(2.0, 2.0);
final AffineTransformOp ato = new AffineTransformOp(at, AffineTransformOp.TYPE_BICUBIC);

Step 5 Apply the transformation

scaledImage = ato.filter(image, scaledImage);

How to resize an image in JDeli

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

BufferedImage image = JDeli.read(bmpFile);

Step 4 Create a transformation

ImageProcessingOperations operations = new ImageProcessingOperations();
operations.scale(scalingFactor);

Step 5 Apply the transform

image = JDeli.process(ImageProcessingOperations operations, 
BufferedImage image);

Why use JDeli process Images in Java?

JDeli offers a range of advantages over ImageIO and alternatives, including:

  • prevent heap related JVM crashes
  • support for additional image formats such as Heic
  • reduce output file size
  • improve read/write performance
  • create smaller files
  • control over output
  • support threading
  • superior image scaling algorithms


Do you need to write or read JPEG in Java?

We have an easy guide on how to write JPEG in Java using ImageIO and JDeli. You can learn how to read/write most of the image files in ImageIO. However, it gives little control over the process.

JDeli is easy to use and offers complete support, so why don't you give a try?

Find out:

Mark Stephens Mark has been working with Java and PDF since 1999 and is a big NetBeans fan. He enjoys speaking at conferences. He has an MA in Medieval History and a passion for reading.

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