Question

In a grails controller I can render an image to the response using

class MyController {

  def getImage = {
    BufferedImage image = ImageIO.read('http://example.org/foo.png')
    ImageIO.write(captcha, "PNG", response.outputStream)
  }
}

In a GSP I can render this image using:

<img src="${createLink(controller: 'my', action: 'getImage')}"/>

I would like to write a TagLib that does something similar.

class MyTagLib {
  static namespace = "my"

  def getImage(attrs ->
    BufferedImage image = ImageIO.read('http://example.org/foo.png')            
  }    
}

But I can’t figure out how to render this image to the response. Inside the tag class, I can only write to out which is an instance of GrailsPrintWriter, but ImageIO.write can only write to an OutputStream.

For the sake of completion, the tag above would be invoked from a GSP using

<my:getImage/>

Answer 1

You can make a writer instance of the GrailsPrintWriter, by doing new WriterOutputStream(out). Try this:

BufferedImage image = ImageIO.read(new URL('http://www.google.de/images/srpr/logo3w.png'))
ImageIO.write(image, "png", new WriterOutputStream(out))

(tested in grails 2.0)