Making Pen

procedure TXBitmap.setPenwidth(w : byte);
//make pen image
var i,j : byte;
h,v,r,r2 : single;
mask : DWORD;
begin
if w = FXpenwidth then exit;
if w > 32 then w := 32;
FXpenwidth := w;
FXpenBias := (w-1) shr 1;

//------- make pen image --------------------

for i := 0 to 31 do FXpen[i] := 0;//erase pen
r := w/2;
r2 := r * r;
for j := 0 to (w-1) shr 1 do // j is vertical movement over half height
begin
v := r - (0.5 + j);
for i := 0 to (w-1) shr 1 do // i is horizontal movement over half width
begin
h := r - (0.5 + i);
if h*h + v*v <= r2 then // pythagoras lemma
begin
mask := 1 shl i;
mask := mask or (1 shl (w-i-1)); // horizontal copy bit
FXpen[j] := FXpen[j] or mask; // set bits
FXpen[w-j-1] := FXpen[w-j-1] or mask; // vertical copy bits
end;//if
end;//for i
end;//for j
end;