temp

procedure TNalaBitmap.Thumbnail(NewWidth, NewHeight: UInt32; TargetBitmap: TNalaBitmap);
var
  w,h,x,y,rx,ry,dx,dy:Int32;
  xx,yy,r,g,b,n,rr,gg,bb:Int32;
  wr,hr:Double;
  TargetData,rowPtr:PRGB32;
  offset:PtrUInt;
begin
  TargetBitmap.SetSize(NewWidth, NewHeight);
  TargetData := TargetBitmap.FData;

  wr := FWidth / NewWidth;
  hr := FHeight / NewHeight;
  w := FWidth - 1;
  h := FHeight - 1;

  for y:=0 to NewHeight - 1 do
  begin
    ry := Trunc(y*hr);
    dy := Min(ry+Trunc(hr), h);
    for x:=0 to NewWidth - 1 do
    begin
      rx := Trunc(x*wr);
      dx := Min(rx+Trunc(wr), w);
      r := 0;
      g := 0;
      b := 0;
      n := 0;
      rowPtr := @FData[ry * FWidth];
      offset := PtrUInt(@FData[dy * FWidth]);
      while PtrUInt(rowPtr) <= offset do
      begin
        for xx:=rx to dx do
        begin
          R += rowPtr[xx].R;
          G += rowPtr[xx].G;
          B += rowPtr[xx].B;
          Inc(n);
        end;
        Inc(rowPtr,FWidth);
      end;
      r := r div n;
      g := g div n;
      b := b div n;

      Ptr := @TargetData[y * NewWidth + x];
      Ptr^.R := r;
      Ptr^.G := g;
      Ptr^.B := b;
    end;
  end;
end;