compress images

Can someone help me?
I need to compress picture files in 320x200 for my game, and I don't know how!
No palette info is needed to save. My code now is:

Procedure PictureSave(Nome:string);
Type IMAGE = array[0..319,0..199] of byte;
Var I,G        : integer;
    pixel        : byte;
    PICT       : ^IMAGE;
    f                : file of IMAGE;
Begin
  New(PICT);
  For I:=0 to 199 do
  Begin
    For G:=0 to 319 do
      PICT^[G,I]:=Getpixel(G,I);
  end;

  Assign(f,NOME+'.PIC');
  Rewrite(f);
  Write(f,PICT^);
  Close(f);
  Dispose(PICT);
end;