static public IsohypseMovement GetOppositeMovement(IsohypseMovement movement)
{
switch (movement)
{
case IsohypseMovement.East:
return(IsohypseMovement.West);
case IsohypseMovement.North:
return(IsohypseMovement.South);
case IsohypseMovement.South:
return(IsohypseMovement.North);
case IsohypseMovement.West:
return(IsohypseMovement.East);
default:
return(IsohypseMovement.None);
}
}
private IsohypseMovements ExtractIsohypseMovements(
IRasterDigitalElevationModel dem,
double isohypseElevation,
Array2 <IsohypseMovement> movements,
Array2 <byte> flags,
int startingX,
int startingY)
{
IsohypseMovements isohypseMovements = new IsohypseMovements(isohypseElevation);
isohypseMovements.StartingX = startingX;
isohypseMovements.StartingY = startingY;
int x = isohypseMovements.StartingX;
int y = isohypseMovements.StartingY;
int lastX = 0, lastY = 0;
IsohypseMovement lastMovement = IsohypseMovement.None;
bool foundOneEnd = false;
while (true)
{
// if we reached the end of the grid
if (x < 0 || y < 0 || x >= dem.LonLength - 1 || y >= dem.LatLength - 1)
{
// have we already found one end of the segment?
if (false == foundOneEnd)
{
// we haven't...
foundOneEnd = true;
// ... so reverse the segment and start moving from the other end
int oldStartingX = isohypseMovements.StartingX;
int oldStartingY = isohypseMovements.StartingY;
isohypseMovements.ReverseIsohypseMovements(x, y);
x = oldStartingX;
y = oldStartingY;
}
else
{
// we have, so we can exit
break;
}
}
if (x == isohypseMovements.StartingX &&
y == isohypseMovements.StartingY &&
isohypseMovements.Movements.Count > 0)
{
// we found the starting point, this is a closed polygon
isohypseMovements.IsClosed = true;
break;
}
IsohypseMovement currentCellMovement = movements.GetValue(x, y);
bool movementFound = false;
for (int i = 0; i < 4; i++)
{
IsohypseMovement movementConsidered = (IsohypseMovement)(1 << i);
if (0 != (currentCellMovement & movementConsidered))
{
int nextX = x, nextY = y;
switch (movementConsidered)
{
case IsohypseMovement.East:
nextX++;
break;
case IsohypseMovement.North:
nextY--;
break;
case IsohypseMovement.South:
nextY++;
break;
case IsohypseMovement.West:
nextX--;
break;
default:
throw new NotImplementedException();
}
// find the opposite movement of the last movement
IsohypseMovement oppositeMovement = IsohypseMovements.GetOppositeMovement(lastMovement);
if (lastMovement != IsohypseMovement.None)
{
// check that we haven't moved back
if (nextX == lastX && nextY == lastY)
{
continue;
}
// special case when all movements are possible
if ((((int)currentCellMovement) & 0xf) == 0xf)
{
IsohypseMovement movementCombination = movementConsidered | oppositeMovement;
// check that we haven't moved in such a way as to make the polygon cross itself
if ((movementCombination & (IsohypseMovement.North | IsohypseMovement.South))
== (IsohypseMovement.North | IsohypseMovement.South))
{
continue;
}
// check that we haven't moved in such a way as to make the polygon cross itself
if ((movementCombination & (IsohypseMovement.West | IsohypseMovement.East))
== (IsohypseMovement.West | IsohypseMovement.East))
{
continue;
}
// check that the movement is the right one in regards to cells elevations
if (flags.GetValue(x, y) == 5)
{
if (movementCombination == (IsohypseMovement.South | IsohypseMovement.East) ||
movementCombination == (IsohypseMovement.North | IsohypseMovement.West))
{
continue;
}
}
else if (flags.GetValue(x, y) == 10)
{
if (movementCombination == (IsohypseMovement.South | IsohypseMovement.West) ||
movementCombination == (IsohypseMovement.North | IsohypseMovement.East))
{
continue;
}
}
else
{
throw new NotImplementedException();
}
}
}
isohypseMovements.Movements.Add(movementConsidered);
// remove the used movement from the array
movements.SetValue(movements.GetValue(x, y) & ~movementConsidered, x, y);
// remove this opposite movement from the array
movements.SetValue(movements.GetValue(x, y) & ~oppositeMovement, x, y);
lastX = x;
lastY = y;
lastMovement = movementConsidered;
x = nextX;
y = nextY;
movementFound = true;
break;
}
}
if (movementFound == false)
{
throw new NotImplementedException();
}
}
return(isohypseMovements);
}
