FUNCTION

MUI is able to uncompress byte&run compressed BODY chunks automatically. If your data is compressed, you must supply a value of cmpByteRun1 (==1) for this tag. Other compression techniques are not supported.

Omitting this tag or setting it to 0 indicates that the BODY data is uncompressed. Using the Bodychunk class doesn't make much sense in this case since its main purpose is to save memory for big images.