EkgBmp:=TBitmap.Create;
EkgBmp.LoadFromFile(....)

jpg:=TJpegImage.Create;
jpg.LoadFromFile(....);
jpg.DIBNeeded;
EkgBmp.Assign(jpg);
jpg.Free;

x,y: Integer;
br,brmin,brmax: Real
scn: PByteArray;
......
brmin:= 1000000000 ; brmax:= 0 ;
 for  y:= 0   to  EkgBmp.Height- 1   do   begin 
  scn:=EkgBmp.ScanLine[y];
   for  x:= 0   to  EkgBmp.Width- 1   do   begin 
    br:=scn[ 3 *x]*scn[ 3 *x]+scn[ 3 *x+ 1 ]*scn[ 3 *x+ 1 ]+scn[ 3 *x+ 2 ]*scn[ 3 *x+ 2 ];
    brmin:=Min(brmin,br);
    brmax:=Max(brmax,br);
   end ;
 end ;

ekg1,ekg2:  array  [...]  of  Integer;
firstx,lastx: Integer;

 for  x:= 0   to  High(ekg1)  do   begin 
  ekg1[x]:= 0 ;
  ekg2[x]:= 0 ;
 end ;
firstx:= 1000000 ;
lastx:= 0 ;
 for  y:= 0   to  EkgBmp.Height- 1   do   begin 
  scn:=EkgBmp.ScanLine[y];
   for  x:= 0   to  EkgBmp.Width- 1   do   begin 
    br:=scn[ 3 *x]*scn[ 3 *x]+scn[ 3 *x+ 1 ]*scn[ 3 *x+ 1 ]+scn[ 3 *x+ 2 ]*scn[ 3 *x+ 2 ];
     if  br<brlim  then   begin 
      ekg1[x]:=y;
       if  ekg2[x]= 0   then  ekg2[x]:=y;
      firstx:=Min(firstx,x);
      lastx:=Max(lastx,x);
     end ;
   end ;
 end ;

 for  x:= 0   to  High(ekg1)  do  ekg1[x]:=(ekg1[x]+ekg2[x])/ 2 ;