wraps java.io.InputStream by scala.collection.immutable.Stream

gistfile1.scala

val stream = fromInputStream(new java.io.FileInputStream("test.jpg"), 8 * 1024)

/**
 * Makes Stream which reads every bytes with specified size from java.io.InputStream.
 */
@tailrec
def fromInputStream(in: java.io.InputStream, bufferSize: Int): Stream[Array[Byte]] = {
  val buffer = new Array[Byte](bufferSize)
  in.read(buffer) match {
    case -1  => Stream.empty
    case len => buffer.slice(0, len) #:: fromInputStream(in, bufferSize)
  }
}

直接FileInputStreamとか読むならある程度のサイズをまとめて読んだほうが圧倒的に速いです。
BufferedInputStreamかましたときは…どうなんでしょう。