I had the need to scale some large JPG images from my camera so I whipped up a quick little Groovy script to do the trick. Thought I would share.

// groovy ScaleImages.groovy DIRNAME SCALE%

import javax.imageio.ImageIO
import java.io.File
import java.awt.Image
import java.awt.Color
import java.awt.image.BufferedImage

class ScaleImages {

    static void main(String[] args){
        def directory = new File(args[0])
        if(!directory.isDirectory()){
            System.out.println("You must specify a valid directory!")
            System.exit(0)
        }

        def scale = Integer.valueOf(args[1])

        directory.eachFile {
            def image = ImageIO.read(it)
            int w = image.getWidth() * scale / 100
            int h = image.getHeight() * scale / 100

            def scaled = image.getScaledInstance(w,h,Image.SCALE_SMOOTH)

            def newImage = new BufferedImage(w,h,image.getType())
            def graphics = newImage.createGraphics()
            graphics.drawImage(scaled,0,0,w,h,Color.white,null)

            if(ImageIO.write(newImage,"jpg",new File(it.getParent(),"scaled_" + it.getName()))){
                System.out.println("scaled: " + it);
            } else {
                System.out.println("failed: " + it);
            }
        }
    }
}

It’s pretty simple. You load the image file to create a BufferedImage. You then create a scaled Image and draw it onto the new empty BufferedImage and save it off. I would recommend some performance enhancements if you are doing huge batches of images but for a directory containing a handful of images it works great and pretty fast. Also, note that this does not handle sub-directories of images, only the directory that you give it.