anchor.diff:  
           let writeImage (size : V2i) (blocks : list<V3i[]>) =
               let ms = new System.IO.MemoryStream()
  -            
  +            let coder = Huffman.photoshop
   
               let header = [| 0xFFuy; 0xD8uy;  |]
               ms.Write(header, 0, header.Length)
  
positive.code:                 let v = uint16 (off + v)
  
                  let index = (byte leadingZeros <<< 4) ||| byte dc
                  let huff = Huffman.acChromInv.[int index]
                  x.Write huff
                  x.Write(Codeword(byte dc, v))
  
          let writeBlock (bs : BitStream) (block : V3i[]) =
  
  
              bs.WriteDCLum(block.[0].X)
              let mutable leading = 0
  
negative.code:                 let v = uint16 (off + v)
  
                  let index = (byte leadingZeros <<< 4) ||| byte dc
                  let huff = coder.acLumInv.[int index]
                  x.Write huff
                  x.Write(Codeword(byte dc, v))
  
  