/**
* A common helper method to initialize a table of precomputed score values using a cubic curve
* @param curve the curve
* @param numSamples the number of samples to compute
* @return the score array table
*/
static private double[] initCubicCurveScoreTable(CubicCurve2D curve, int numSamples)
{
double x1 = curve.X1;
double x2 = curve.X2;
double range = x2 - x1;
double x = x1;
double xInc = range / numSamples; // even incrementer to increment x value by when sampling across the curve
double[] scoreTable = new double[numSamples];
// For use to pass into with solveCubicCurve
double[] solutions = new double[1];
// Sample evenly across the curve and set the samples into the table.
for (int i = 0; i < numSamples; i++)
{
//CurveUtils.solveCubicCurveForX(curve, Math.Min(x, x2), solutions);
//double t = solutions[0];
double t = curve.GetFirstSolutionForX(Math.Min(x, x2));
//scoreTable[i] = CurveUtils.getPointOnCubicCurve(curve, t).getY();
scoreTable[i] = curve.GetYOnCurve(t);
x += xInc;
}
return(scoreTable);
}
/**
* Computes the range of substrokes to use when computing matches based on looseness.
* When matching, sub strokes are matched up with one another to find the best
* matching. But if two substrokes are +/- beyond this range, then the comparison
* is short-circuited for some computation savings.
*
* @param subStrokeCount the substroke count of the input character
* @param looseness the looseness, 0-1
* @return the range
*/
private int getSubStrokesRange(int subStrokeCount)
{
// Return the maximum if looseness = 1.0.
// Otherwise we'd have to ensure that the floating point value led to exactly the right int count.
if (looseness == 1.0)
{
return(CharacterDescriptor.MAX_CHARACTER_SUB_STROKE_COUNT);
}
// We use a CubicCurve that grows slowly at first and then rapidly near the end to the maximum.
double y0 = subStrokeCount * 0.25;
double ctrl1X = 0.4;
double ctrl1Y = 1.5 * y0;
double ctrl2X = 0.75;
double ctrl2Y = 1.5 * ctrl1Y;
double[] solutions = new double[1];
CubicCurve2D curve = new CubicCurve2D(0, y0, ctrl1X, ctrl1Y, ctrl2X, ctrl2Y, 1, CharacterDescriptor.MAX_CHARACTER_SUB_STROKE_COUNT);
//CurveUtils.solveCubicCurveForX(curve, looseness, solutions);
//double t = solutions[0];
double t = curve.GetFirstSolutionForX(looseness);
// We get the t value on the parametrized curve where the x value matches the looseness.
// Then we compute the y value for that t. This gives the range.
//return (int)Math.Round(CurveUtils.getPointOnCubicCurve(curve, t).getY());
return((int)Math.Round(curve.GetYOnCurve(t)));
}
/**
* Computes a range of strokes to use based on the given looseness.
* Only characters whose number of strokes are within the input number of strokes
* +/- this range will be considered during comparison. This helps cut down
* on matching cost.
*
* @param strokeCount the number of input strokes
* @param looseness the looseness, 0-1
* @return the range
*/
private int getStrokesRange(int strokeCount)
{
// Just return some extreme values if at minimum or maximum.
// Helps to avoid possible floating point issues when near the extremes.
if (looseness == 0.0)
{
return(0);
}
else if (looseness == 1.0)
{
return(CharacterDescriptor.MAX_CHARACTER_STROKE_COUNT);
}
// We use a CubicCurve that grows slowly at first and then rapidly near the end to the maximum.
// This is so a looseness at or near 1.0 will return a range that will consider all characters.
double ctrl1X = 0.35;
double ctrl1Y = strokeCount * 0.4;
double ctrl2X = 0.6;
double ctrl2Y = strokeCount;
double[] solutions = new double[1];
CubicCurve2D curve = new CubicCurve2D(0, 0, ctrl1X, ctrl1Y, ctrl2X, ctrl2Y, 1, CharacterDescriptor.MAX_CHARACTER_STROKE_COUNT);
//CurveUtils.solveCubicCurveForX(curve, looseness, solutions);
//double t = solutions[0];
double t = curve.GetFirstSolutionForX(looseness);
// We get the t value on the parametrized curve where the x value matches the looseness.
// Then we compute the y value for that t. This gives the range.
//return (int)Math.Round(CurveUtils.getPointOnCubicCurve(curve, t).getY());
return((int)Math.Round(curve.GetYOnCurve(t)));
}
/**
* Builds a precomputed array of values to use when getting the score between two substroke directions.
* Two directions should differ by 0 - Pi, and the score should be the (difference / Pi) * score table's length
*
* @return the direction score table
*/
static private double[] initDirectionScoreTable()
{
// The curve drops as the difference grows, but rises again some at the end because
// a stroke that is 180 degrees from the expected direction maybe OK passable.
CubicCurve2D curve = new CubicCurve2D(0, 1.0, 0.5, 1.0, 0.25, -2.0, 1.0, 1.0);
return(initCubicCurveScoreTable(curve, 100));
}
/**
* Builds a precomputed array of values to use when getting the score between two substroke lengths.
* A ratio less than one is computed for the two lengths, and the score should be the ratio * score table's length.
*
* @return the length score table
*/
static private double[] initLengthScoreTable()
{
// Curve grows rapidly as the ratio grows and levels off quickly.
// This is because we don't really expect lengths to vary a lot.
// We are really just trying to distinguish between tiny strokes and long strokes.
CubicCurve2D curve = new CubicCurve2D(0, 0, 0.25, 1.0, 0.75, 1.0, 1.0, 1.0);
return(initCubicCurveScoreTable(curve, 100));
}
