Error when using itext to merge Pdfs via byte array in RJB

Question

Using rjb with ruby 1.9.3 and itext 4.2.0:

What I'm trying to do is to merge tiff files into pdfs. However, I would like to the merge to happen in memory rather than saving the conversion of the tiff to pdf to a file and then running a combine on the files. Rather than supply PdfReader with a filename, I have seen some examples saying it can also take a Byte Array as an input. I can get the file version working, but I get an error when I use a ByteArrayOutStream, and I'm not sure why.

The following seems to work fine when using a filestream:

def tiff_to_pdf_by_file(image_file_name)
  @document = Rjb::import('com.lowagie.text.Document')

  @tifreader = Rjb::import('com.lowagie.text.pdf.codec.TiffImage')
  @randomaccess = Rjb::import('com.lowagie.text.pdf.RandomAccessFileOrArray')

  @pdfwriter = Rjb::import('com.lowagie.text.pdf.PdfWriter')
  @filestream    = Rjb::import('java.io.FileOutputStream')

  pdf = @document.new

  @pdfwriter.getInstance(pdf, @filestream.new('test_temp.pdf'))

  pdf.open()

  ra = @randomaccess.new(image_file_name)
  pages = @tifreader.getNumberOfPages(ra)

  (1..pages).each do |i|
    image = @tifreader.getTiffImage(ra,i)
    scaler = ((pdf.getPageSize().getWidth() - pdf.leftMargin() - pdf.rightMargin()) / image.getWidth() * 100)
    image.scalePercent(scaler)
    pdf.add(image)
  end

  pdf.close()

  return 'test_temp.pdf'
end

@pdfreader     = Rjb::import('com.lowagie.text.pdf.PdfReader')
@pdfcopyfields = Rjb::import('com.lowagie.text.pdf.PdfCopyFields')
@filestream    = Rjb::import('java.io.FileOutputStream')
filestream = @filestream.new('new_combined_pdf.pdf')
copy = @pdfcopyfields.new(filestream)
copy.addDocument(@pdfreader.new(tiff_to_pdf_by_file('test_image.tif')))
copy.addDocument(@pdfreader.new('test_template.pdf))
copy.close()

But when I try to use a byte array like the code below, I get the error "Not found as a file or resource" on the line the pdfreader reads the byte array.

def tiff_to_pdf_by_file(image_file_name)
  @document = Rjb::import('com.lowagie.text.Document')

  @tifreader = Rjb::import('com.lowagie.text.pdf.codec.TiffImage')
  @randomaccess = Rjb::import('com.lowagie.text.pdf.RandomAccessFileOrArray')

  @pdfwriter = Rjb::import('com.lowagie.text.pdf.PdfWriter')
  @bytestream    = Rjb::import('java.io.ByteArrayOutputStream')

  pdf = @document.new

  outstream = @bytestream.new
  @pdfwriter.getInstance(pdf, outstream)

  pdf.open()

  ra = @randomaccess.new(image_file_name)
  pages = @tifreader.getNumberOfPages(ra)

  (1..pages).each do |i|
    image = @tifreader.getTiffImage(ra,i)
    scaler = ((pdf.getPageSize().getWidth() - pdf.leftMargin() - pdf.rightMargin()) / image.getWidth() * 100)
    image.scalePercent(scaler)
    pdf.add(image)
  end

  pdf.close()
  outstream.flush()

  return outstream.toByteArray()
end

@pdfreader     = Rjb::import('com.lowagie.text.pdf.PdfReader')
@pdfcopyfields = Rjb::import('com.lowagie.text.pdf.PdfCopyFields')
@filestream    = Rjb::import('java.io.FileOutputStream')
filestream = @filestream.new('new_combined_pdf.pdf')
copy = @pdfcopyfields.new(filestream)
copy.addDocument(@pdfreader.new(tiff_to_pdf_by_file('test_image.tif')))
copy.addDocument(@pdfreader.new('test_template.pdf))
copy.close()