question: public static void extractIdat ( InputStream is , OutputStream os , boolean stripFilterByte , boolean checkCrc ) { try { ChunkSeqPngRawPixels cr = new ChunkSeqPngRawPixels ( is , os ) ; cr . setCheckCrc ( checkCrc ) ; cr . setOmitFilterByte ( stripFilterByte ) ; cr . readAll ( ) ; is . close ( ) ; os . close ( ) ; } catch ( IOException e ) { throw new PngjException ( e ) ; } }
target:  reads a PNG and and writes the uncompressed unfiltered raw stream to os 