Naïve 2D cross-correlation

program new;
{$DEFINE E_HIDE_ALL}
{$I SimbaExt_beta/SimbaExt.simba}

function MatchTemplate(im,sub:TIntMatrix): TFloatMatrix;
type
  TRGBMatrix = Array of Array of TRGB32;
var
  ImW,ImH,SubW,SubH,area:Int32;
  x,y,xx,yy,iw,ih:Int32;
  cc:Int64;
  pix1,pix2:TRGB32;
  i1,i2:TRGBMatrix;
const
  MAX_SQRGB:Double = (255*255*3.0);
begin
  ImW := Length(Im[0]);
  ImH := Length(Im);
  SubW := Length(Sub[0]);
  SubH := Length(Sub);

  SetLength(Result, ImH-SubH, ImW-SubW);
  ih := subh-1;
  iw := subw-1;
  area := subW * subH;
  i1 := TRGBMatrix(im);
  i2 := TRGBMatrix(sub);

  for y:=0 to ImH-SubH-1 do
    for x:=0 to ImW-SubW-1 do
    begin
      cc := 0;
      for yy:=0 to ih do
        for xx:=0 to iw do
          Inc(cc, Sqr(i1[y+yy,x+xx].B - i2[yy,xx].B) +
                  Sqr(i1[y+yy,x+xx].G - i2[yy,xx].G) +
                  Sqr(i1[y+yy,x+xx].R - i2[yy,xx].R) );
      Result[y,x] := 1 - (cc / area / MAX_SQRGB); //Result range in 0..1
    end;
end;

procedure Debug(Mat:TFloatMatrix);
var
  Debug:TRafBitmap;
  Data:TIntMatrix;
  x,y:Int32;
  H,S,L:Extended;
begin
  Mat := Mat.Normalize(0,100);
  SetLength(Data,Length(Mat), Length(Mat[0]));
  for y:=0 to High(Mat) do
    for x:=0 to High(Mat[0]) do
    begin
      //ColorToHSL(Mat[y,x],H,S,L);
      H := 58;
      S := Mat[y,x];
      L := Mat[y,x];
      Data[y,x] := HSLToColor(H,S,L);
    end;
  Debug.FromMatrix( Data );
  Debug.Debug();
  Debug.Free();
end;

var
  BMP,SUB:TRafBitmap;
  Mat:TFloatMatrix;
  m1,m2:TIntMatrix;
  t:Double;
begin
  SUB.Open('rs_cave_sub.png');
  BMP.Open('rs_cave.png');

  m1 := BMP.ToMatrix();
  m2 := Sub.ToMatrix();
  t := se.MarkTime();
  mat := MatchTemplate(m1, m2);
  WriteLn(se.MarkTime() - t);
  Debug( mat );
end.