/// <summary>
/// <p>This is called when a horizontal scan finds a possible alignment pattern. It will
/// cross check with a vertical scan, and if successful, will, ah, cross-cross-check
/// with another horizontal scan. This is needed primarily to locate the real horizontal
/// center of the pattern in cases of extreme skew.
/// And then we cross-cross-cross check with another diagonal scan.</p>
/// If that succeeds the finder pattern location is added to a list that tracks
/// the number of times each location has been nearly-matched as a finder pattern.
/// Each additional find is more evidence that the location is in fact a finder
/// pattern center
/// </summary>
/// <param name="stateCount">reading state module counts from horizontal scan</param>
/// <param name="i">row where finder pattern may be found</param>
/// <param name="j">end of possible finder pattern in row</param>
/// <param name="pureBarcode">true if in "pure barcode" mode</param>
/// <returns>
/// true if a finder pattern candidate was found this time
/// </returns>
protected bool handlePossibleCenter(int[] stateCount, int i, int j, bool pureBarcode)
{
int stateCountTotal = stateCount[0] + stateCount[1] + stateCount[2] + stateCount[3] +
stateCount[4];
float?centerJ = centerFromEnd(stateCount, j);
if (centerJ == null)
{
return(false);
}
float?centerI = crossCheckVertical(i, (int)centerJ.Value, stateCount[2], stateCountTotal);
if (centerI != null)
{
// Re-cross check
centerJ = crossCheckHorizontal((int)centerJ.Value, (int)centerI.Value, stateCount[2], stateCountTotal);
if (centerJ != null &&
(!pureBarcode || crossCheckDiagonal((int)centerI, (int)centerJ, stateCount[2], stateCountTotal)))
{
float estimatedModuleSize = stateCountTotal / 7.0f;
bool found = false;
for (int index = 0; index < possibleCenters.Count; index++)
{
var center = possibleCenters[index];
// Look for about the same center and module size:
if (center.aboutEquals(estimatedModuleSize, centerI.Value, centerJ.Value))
{
possibleCenters.RemoveAt(index);
possibleCenters.Insert(index, center.combineEstimate(centerI.Value, centerJ.Value, estimatedModuleSize));
found = true;
break;
}
}
if (!found)
{
var point = new FinderPattern(centerJ.Value, centerI.Value, estimatedModuleSize);
possibleCenters.Add(point);
if (resultPointCallback != null)
{
resultPointCallback(point);
}
}
return(true);
}
}
return(false);
}
/// <returns> the 3 best {@link FinderPattern}s from our list of candidates. The "best" are
/// those that have been detected at least {@link #CENTER_QUORUM} times, and whose module
/// size differs from the average among those patterns the least
/// </returns>
private FinderPattern[] selectBestPatterns()
{
int startSize = possibleCenters.Count;
if (startSize < 1)
{
// Couldn't find enough finder patterns
return(null);
}
// Filter outlier possibilities whose module size is too different
if (startSize > 3)
{
// But we can only afford to do so if we have at least 4 possibilities to choose from
float totalModuleSize = 0.0f;
float square = 0.0f;
foreach (var center in possibleCenters)
{
float size = center.EstimatedModuleSize;
totalModuleSize += size;
square += size * size;
}
float average = totalModuleSize / startSize;
float stdDev = (float)Math.Sqrt(square / startSize - average * average);
possibleCenters.Sort(new FurthestFromAverageComparator(average));
float limit = Math.Max(0.2f * average, stdDev);
for (int i = 0; i < possibleCenters.Count && possibleCenters.Count > 3; i++)
{
FinderPattern pattern = possibleCenters[i];
if (Math.Abs(pattern.EstimatedModuleSize - average) > limit)
{
possibleCenters.RemoveAt(i);
i--;
}
}
}
if (possibleCenters.Count > 3)
{
// Throw away all but those first size candidate points we found.
float totalModuleSize = 0.0f;
foreach (var possibleCenter in possibleCenters)
{
totalModuleSize += possibleCenter.EstimatedModuleSize;
}
float average = totalModuleSize / possibleCenters.Count;
possibleCenters.Sort(new CenterComparator(average));
//possibleCenters.subList(3, possibleCenters.Count).clear();
possibleCenters = possibleCenters.GetRange(0, 3);
}
/*
* return new[]
* {
* possibleCenters[0],
* possibleCenters[1],
* possibleCenters[2]
* };
*/
return(new[]
{
possibleCenters[0]
});
}
