Algorithms

rotated_x =  x * cos(alpha) + y * sin(alpha)
rotated_y = -x * sin(alpha) + y * cos(alpha)

new_height = abs(-width * sin(alpha) + height * cos(alpha))

abs(-width * sin(alpha)) + abs(height * cos(alpha))
    ^
    |
    +- This is the minus that you are talking about, I suppose

abs(-x * sqrt(2) / 2 + x * sqrt(2) / 2)

abs(-x * a + x * a)

abs(0)

for x = 0 to xmax
  for y = 0 to ymax
    if (CI(x,y) > CI(x-1,y) || CI(x,y) > CI(x+1,y) || CI(x,y) > CI(x,y-1) || CI(x,y) > CI(x,y+1))
      set_line_colour(x,y);

int CI(int x, int y) 
{
  return (int)(altitude[x,y] / contour_interval);
}

Mark Nischalke wrote:

bool result = [What algorithm goes here];

private void TestAll()
{
    Test(false, false, false, false, false, false, false);
    Test(false, false, false, false, true, true, true); 
    Test(false, false, false, false, true, false, false);
    Test(false, false, true, false, true, true, false);
    Test(false, false, true, true, true, true, true);
}

private bool Test(bool f, bool fl, bool d, bool dl, bool r, bool rl, bool expected)
{
    bool result=Logic(bool f, bool fl, bool d, bool dl, bool r, bool rl);
    bool OK=result==expected;
    System.Diagnostics.Debug.Assert(OK, "Test failed: "+f+f1+d+d1+r+r1+result+expected);
    return OK;
}

private bool Logic(bool f, bool fl, bool d, bool dl, bool r, bool rl, bool expected)
{
    bool result = ???;
    return result;
}

bool mf = f==f1;
bool md = d==d1;
bool mr = r==r1;
bool result=mf && md && mr && (f||d||r);