What is the best way to scale images in Java?

I have a web application written in Java (Spring, Hibernate/JPA, Struts2) where users can upload images and store them in the file system. I would like to scale those images so that they are of a consistent size for display on the site. What libraries or built in functions will offer the best results? I will consider the following criteria in making my decision (in this order):

• Free/Open Source (essential)
• Easy to implement
• Quality of results
• Performance
• Size of executable

From stackoverflow

• Have a look at the Java Image I/O API to read/write the image. Then use AffineTransform to resize.

  Also, here's a complete example using java.awt.Image.

• Look into also to java-image-scaling library. It created better quality images that ImageIO.