capture process output in Groovy

I have a Groovy script that recurses through a directory looking for .png files, and invokes pngquant (a command-line utility) on each of. The output of pngquant should be printed on the terminal. The relevant code is:

def command = "pngquant -f -ext .png"

root.eachFileRecurse(groovy.io.FileType.FILES) {File file ->

    if (file.name.endsWith('.png')) { 
        println "Compressing file: $file"

        def imgCommand = "$command $file.absolutePath"

        Process pngquantCmd = imgCommand.execute()
        pngquantCmd.consumeProcessOutput(System.out, System.err)        
    }
}

The script works fine, but once all the files have been processed, it seems that stout is still being redirected, because the command-prompt never appears unless I kill the process with Ctrl + C. Do I need to somehow "undo"

pngquantCmd.consumeProcessOutput(System.out, System.err)        

or is there a better way to redirect the output of this process to the console? I guess I could solve this problem simply by adding System.exit(0), but this doesn't seem like the right solution. The problem only occurs on Linux.