public GeneralMatrix QuantizeScreen(int grid_x, int grid_y)
{
// create a general matrix full of 0s
GeneralMatrix mesh = new GeneralMatrix(grid_x, grid_y, 0.0);
// Find the bounding box of the points.
System.Drawing.Rectangle bBox = BoundingBox();
if (_points.Count == 0)
{
return(mesh);
}
// find the step we want
// Note: this is an intentional deviation from the original paper.
// We do not maintain the original aspect ratio of the shape.
double stepX = bBox.Width / (double)(grid_x - 1);
double stepY = bBox.Height / (double)(grid_y - 1);
// find the center of the image
double cx = (double)(bBox.Left + bBox.Right) / 2.0;
double cy = (double)(bBox.Top + bBox.Bottom) / 2.0;
foreach (GenericPoint pt in _points)
{
// normalize the point's coordinates
int x_index = (int)Math.Floor(((pt.X - cx) / stepX) + grid_x / 2);
int y_index = (int)Math.Floor(((pt.Y - cy) / stepY) + grid_y / 2);
if (x_index < grid_x && y_index < grid_y)
{
mesh.SetElement(y_index, x_index, 1.0);
}
}
#if JESSI
Console.WriteLine("Quantized screen");
Console.Write(mesh.ToString());
#endif
return(mesh);
}
/// <summary>
/// Calculates and saves the distance transform map for the polar coordinates.
/// Uses _pMesh and saves to _pDTM.
/// A distance transform map is a matrix in which every entry represents the
/// distance from that point to the nearest point with ink.
/// </summary>
private void PolarDistanceTransform()
{
List <Coord> indices = IndexList(_pMesh);
for (int i = 0; i < GRID_Y_SIZE; i++)
{
for (int j = 0; j < GRID_X_SIZE; j++)
{
Coord cp = new Coord(j, i);
double mindist = double.PositiveInfinity;
foreach (Coord pt in indices)
{
// the straight distance between current point and current index
double dx = Math.Abs(cp.X - pt.X);
double dy = Math.Abs(cp.Y - pt.Y);
double straightDist = Math.Sqrt(dx * dx + dy * dy);
dx = (double)GRID_X_SIZE - dx;
double wrapDist = Math.Sqrt(dx * dx + dy * dy);
double distan = Math.Min(straightDist, wrapDist);
if (distan < mindist)
{
mindist = distan;
}
}
_pDTM.SetElement(i, j, mindist);
}
}
#if FALSE
Console.WriteLine("Your polar distance transform map:");
Console.Write(_pDTM.ToString())
#endif
}
/// <summary>
/// Calculates the dissimilarity between the calling BitmapSymbol and
/// BitmapSymbol S in terms of their polar coordinates using the
/// modified Hausdorff distance (aka the mean distance).
/// </summary>
private SymbolRank Polar_Mod_Hausdorff(BitmapSymbol S)
{
int lower_rot_index = (int)Math.Floor(ALLOWED_ROTATION_AMOUNT * GRID_X_SIZE / 720.0);
int upper_rot_index = GRID_X_SIZE - lower_rot_index; //trick
List <Coord> A = new List <Coord>(_polarCoords);
List <Coord> B = new List <Coord>(S._polarCoords);
if (A.Count == 0 || B.Count == 0)
{
return(new SymbolRank());
}
double minA2B = double.PositiveInfinity;
double distan = 0.0;
int besti = 0; // the best translation in theta
#if FALSE
Console.WriteLine("Your gate: ");
Console.Write(_pMesh.ToString());
Console.WriteLine("Your template: ");
Console.Write(S._pMesh.ToString());
#endif
// rotations in screen coordinates are the same as translations in polar coords
// we have polar coords, so translate in X (theta) until you get the best orientation
for (int i = 0; i < GRID_X_SIZE; i++)
{
if (i > lower_rot_index && i < upper_rot_index)
{
continue;
}
distan = 0.0;
// find the distance from each point in A to the nearest point in B using B_DTM
foreach (Coord a in A)
{
int y_ind = (int)a.Y;
int x_ind = (int)a.X - i; // translate by i on the theta (X) axis
if (x_ind < 0)
{
x_ind += GRID_X_SIZE; // make sure we're still on the graph
}
//putting less weight on points that have small rel dist - y
double weight = Math.Pow((double)y_ind, POLAR_WEIGHT_DECAY_RATE);
distan += S._pDTM.GetElement(y_ind, x_ind) * weight;
}
// this is the best orientation if the total distance is the smallest
if (distan < minA2B)
{
minA2B = distan;
besti = i;
}
}
// set the best rotation angle (in radians)
double bestRotAngle = besti * 2.0 * Math.PI / (double)GRID_X_SIZE;
// we've already found the best orientation
// find the distance from each point in B to the nearest point in A using A_DTM
double minB2A = 0.0;
foreach (Coord b in B)
{
int y_ind = (int)b.Y;
int x_ind = (int)b.X - besti; // slide B back by besti
if (x_ind < 0)
{
x_ind += GRID_X_SIZE;
}
double weight = Math.Pow((double)y_ind, POLAR_WEIGHT_DECAY_RATE);
minB2A += _pDTM.GetElement(y_ind, x_ind) * weight;
}
minA2B /= (double)A.Count;
minB2A /= (double)B.Count;
#if FALSE
Console.WriteLine("Finding best orientation match of your gate and " + S._name);
Console.WriteLine("The best translation is " + besti + " which is " + bestRotAngle + " radians.");
Console.WriteLine("A2B distance: " + minA2B + ", B2A distance: " + minB2A);
string templateName = S._name;
#endif
return(new SymbolRank(Math.Max(minA2B, minB2A), S, bestRotAngle));
}
