How to resize images in 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)

Download JDeli here