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

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image formats java

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

ImageIO allows the reading and writing of 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 the output file size
  • improve read/write performance
  • create smaller files
  • control over output
  • support threading
  • superior image scaling algorithms


Read and write images in Java with one line of code

Read an Image with

BufferedImage image = JDeli.read(streamOrFile);

and write an Image with

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

Write and Read Images in Java Download JDeli here

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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