[fpc-pascal] Implementing AggPas with PtcGraph

[James Richters]

I was trying to find putimage to see how it worked...  and I came across some notes about it in graph.inc as follows:
{ For significant speed improvements , is is recommended }  
{ that these routines be hooked (otherwise the default,  }
{ slower routines will be used) :                        }
..
{   PutImage()                                           }
..

what does 'these routines be hooked'  mean?  Is that something I should be doing in my program or something that is already done internally with ptcgraph?