/// <returns> number of rows we could safely skip during scanning, based on the first
/// two finder patterns that have been located. In some cases their position will
/// allow us to infer that the third pattern must lie below a certain point farther
/// down in the image.
/// </returns>
private int findRowSkip()
{
int max = possibleCenters.Count;
if (max <= 1)
{
return(0);
}
FinderPattern firstConfirmedCenter = null;
foreach (var center in possibleCenters)
{
if (center.Count >= CENTER_QUORUM)
{
if (firstConfirmedCenter == null)
{
firstConfirmedCenter = center;
}
else
{
// We have two confirmed centers
// How far down can we skip before resuming looking for the next
// pattern? In the worst case, only the difference between the
// difference in the x / y coordinates of the two centers.
// This is the case where you find top left last.
hasSkipped = true;
//UPGRADE_WARNING: Data types in Visual C# might be different. Verify the accuracy of narrowing conversions. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1042'"
return((int)(Math.Abs(firstConfirmedCenter.X - center.X) - Math.Abs(firstConfirmedCenter.Y - center.Y)) / 2);
}
}
}
return(0);
}
/// <summary>
/// Returns the z component of the cross product between vectors BC and BA.
/// </summary>
private static float crossProductZ(FinderPattern pointA, FinderPattern pointB, FinderPattern pointC)
{
float bX = pointB.x;
float bY = pointB.y;
return(((pointC.x - bX) * (pointA.y - bY)) - ((pointC.y - bY) * (pointA.x - bX)));
}
/// <summary>
/// Get square of distance between a and b.
/// </summary>
/// <param name="a"></param>
/// <param name="b"></param>
/// <returns></returns>
private static double squaredDistance(FinderPattern a, FinderPattern b)
{
double x = a.X - b.X;
double y = a.Y - b.Y;
return(x * x + y * y);
}
/// <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);
}
/// <summary>
/// Orders an array of three ResultPoints in an order [A,B,C] such that AB < AC and
/// BC < AC and the angle between BC and BA is less than 180 degrees.
/// </summary>
internal static void orderBestPatterns(FinderPattern[] patterns)
{
// Find distances between pattern centers
float zeroOneDistance = distance(patterns[0], patterns[1]);
float oneTwoDistance = distance(patterns[1], patterns[2]);
float zeroTwoDistance = distance(patterns[0], patterns[2]);
FinderPattern pointA, pointB, pointC;
// Assume one closest to other two is B; A and C will just be guesses at first
if (oneTwoDistance >= zeroOneDistance && oneTwoDistance >= zeroTwoDistance)
{
pointB = patterns[0];
pointA = patterns[1];
pointC = patterns[2];
}
else if (zeroTwoDistance >= oneTwoDistance && zeroTwoDistance >= zeroOneDistance)
{
pointB = patterns[1];
pointA = patterns[0];
pointC = patterns[2];
}
else
{
pointB = patterns[2];
pointA = patterns[0];
pointC = patterns[1];
}
// Use cross product to figure out whether A and C are correct or flipped.
// This asks whether BC x BA has a positive z component, which is the arrangement
// we want for A, B, C. If it's negative, then we've got it flipped around and
// should swap A and C.
if (crossProductZ(pointA, pointB, pointC) < 0.0f)
{
FinderPattern temp = pointA;
pointA = pointC;
pointC = temp;
}
patterns[0] = pointA;
patterns[1] = pointB;
patterns[2] = pointC;
}
/// <summary> <p>Estimates module size based on two finder patterns -- it uses
/// {@link #sizeOfBlackWhiteBlackRunBothWays(int, int, int, int)} to figure the
/// width of each, measuring along the axis between their centers.</p>
/// </summary>
private float calculateModuleSizeOneWay(FinderPattern pattern, FinderPattern otherPattern)
{
//UPGRADE_WARNING: Data types in Visual C# might be different. Verify the accuracy of narrowing conversions. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1042'"
float moduleSizeEst1 = sizeOfBlackWhiteBlackRunBothWays((int)pattern.X, (int)pattern.Y, (int)otherPattern.X, (int)otherPattern.Y);
//UPGRADE_WARNING: Data types in Visual C# might be different. Verify the accuracy of narrowing conversions. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1042'"
float moduleSizeEst2 = sizeOfBlackWhiteBlackRunBothWays((int)otherPattern.X, (int)otherPattern.Y, (int)pattern.X, (int)pattern.Y);
if (Single.IsNaN(moduleSizeEst1))
{
return(moduleSizeEst2 / 7.0f);
}
if (Single.IsNaN(moduleSizeEst2))
{
return(moduleSizeEst1 / 7.0f);
}
// Average them, and divide by 7 since we've counted the width of 3 black modules,
// and 1 white and 1 black module on either side. Ergo, divide sum by 14.
return((moduleSizeEst1 + moduleSizeEst2) / 14.0f);
}
/// <summary> <p>Computes the dimension (number of modules on a size) of the QR Code based on the position
/// of the finder patterns and estimated module size.</p>
/// </summary>
private static bool computeDimension(FinderPattern topLeft, FinderPattern topRight, FinderPattern bottomLeft, float moduleSize, out int dimension)
{
int tltrCentersDimension = MathUtils.round(FinderPattern.distance(topLeft, topRight) / moduleSize);
int tlblCentersDimension = MathUtils.round(FinderPattern.distance(topLeft, bottomLeft) / moduleSize);
dimension = ((tltrCentersDimension + tlblCentersDimension) >> 1) + 7;
switch (dimension & 0x03)
{
// mod 4
case 0:
dimension++;
break;
// 1? do nothing
case 2:
dimension--;
break;
case 3:
return(true);
}
return(true);
}
/// <summary> <p>Computes an average estimated module size based on estimated derived from the positions
/// of the three finder patterns.</p>
/// </summary>
protected internal virtual float calculateModuleSize(FinderPattern topLeft, FinderPattern topRight, FinderPattern bottomLeft)
{
// Take the average
return((calculateModuleSizeOneWay(topLeft, topRight) + calculateModuleSizeOneWay(topLeft, bottomLeft)) / 2.0f);
}
/// <summary>
/// Processes the finder pattern info.
/// </summary>
/// <param name="info">The info.</param>
/// <returns></returns>
protected internal virtual DetectorResult processFinderPatternInfo(FinderPatternInfo info)
{
FinderPattern topLeft = info.TopLeft;
FinderPattern topRight = info.TopRight;
FinderPattern bottomLeft = info.BottomLeft;
float moduleSize = calculateModuleSize(topLeft, topRight, bottomLeft);
if (moduleSize < 1.0f)
{
return(null);
}
int dimension;
if (!computeDimension(topLeft, topRight, bottomLeft, moduleSize, out dimension))
{
return(null);
}
Internal.Version provisionalVersion = Internal.Version.getProvisionalVersionForDimension(dimension);
if (provisionalVersion == null)
{
return(null);
}
int modulesBetweenFPCenters = provisionalVersion.DimensionForVersion - 7;
AlignmentPattern alignmentPattern = null;
// Anything above version 1 has an alignment pattern
if (provisionalVersion.AlignmentPatternCenters.Length > 0)
{
// Guess where a "bottom right" finder pattern would have been
float bottomRightX = topRight.X - topLeft.X + bottomLeft.X;
float bottomRightY = topRight.Y - topLeft.Y + bottomLeft.Y;
// Estimate that alignment pattern is closer by 3 modules
// from "bottom right" to known top left location
//UPGRADE_WARNING: Data types in Visual C# might be different. Verify the accuracy of narrowing conversions. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1042'"
float correctionToTopLeft = 1.0f - 3.0f / (float)modulesBetweenFPCenters;
//UPGRADE_WARNING: Data types in Visual C# might be different. Verify the accuracy of narrowing conversions. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1042'"
int estAlignmentX = (int)(topLeft.X + correctionToTopLeft * (bottomRightX - topLeft.X));
//UPGRADE_WARNING: Data types in Visual C# might be different. Verify the accuracy of narrowing conversions. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1042'"
int estAlignmentY = (int)(topLeft.Y + correctionToTopLeft * (bottomRightY - topLeft.Y));
// Kind of arbitrary -- expand search radius before giving up
for (int i = 4; i <= 16; i <<= 1)
{
alignmentPattern = findAlignmentInRegion(moduleSize, estAlignmentX, estAlignmentY, (float)i);
if (alignmentPattern == null)
{
continue;
}
break;
}
// If we didn't find alignment pattern... well try anyway without it
}
PerspectiveTransform transform = createTransform(topLeft, topRight, bottomLeft, alignmentPattern, dimension);
BitMatrix bits = sampleGrid(image, transform, dimension);
if (bits == null)
{
return(null);
}
ResultPoint[] points;
if (alignmentPattern == null)
{
points = new ResultPoint[] { bottomLeft, topLeft, topRight };
}
else
{
points = new ResultPoint[] { bottomLeft, topLeft, topRight, alignmentPattern };
}
return(new DetectorResult(bits, points));
}
/// <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 < 3)
{
// 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]
});
}
/// <summary> <p>Computes an average estimated module size based on estimated derived from the positions
/// of the three finder patterns.</p>
/// </summary>
protected internal virtual float calculateModuleSize(FinderPattern topLeft, FinderPattern topRight, FinderPattern bottomLeft)
{
// Take the average
return (calculateModuleSizeOneWay(topLeft, topRight) + calculateModuleSizeOneWay(topLeft, bottomLeft)) / 2.0f;
}
/// <summary>
/// Returns the z component of the cross product between vectors BC and BA.
/// </summary>
private static float crossProductZ(FinderPattern pointA, FinderPattern pointB, FinderPattern pointC)
{
float bX = pointB.x;
float bY = pointB.y;
return ((pointC.x - bX) * (pointA.y - bY)) - ((pointC.y - bY) * (pointA.x - bX));
}
/// <summary>
/// Orders an array of three ResultPoints in an order [A,B,C] such that AB < AC and
/// BC < AC and the angle between BC and BA is less than 180 degrees.
/// </summary>
internal static void orderBestPatterns(FinderPattern[] patterns)
{
// Find distances between pattern centers
float zeroOneDistance = distance(patterns[0], patterns[1]);
float oneTwoDistance = distance(patterns[1], patterns[2]);
float zeroTwoDistance = distance(patterns[0], patterns[2]);
FinderPattern pointA, pointB, pointC;
// Assume one closest to other two is B; A and C will just be guesses at first
if (oneTwoDistance >= zeroOneDistance && oneTwoDistance >= zeroTwoDistance)
{
pointB = patterns[0];
pointA = patterns[1];
pointC = patterns[2];
}
else if (zeroTwoDistance >= oneTwoDistance && zeroTwoDistance >= zeroOneDistance)
{
pointB = patterns[1];
pointA = patterns[0];
pointC = patterns[2];
}
else
{
pointB = patterns[2];
pointA = patterns[0];
pointC = patterns[1];
}
// Use cross product to figure out whether A and C are correct or flipped.
// This asks whether BC x BA has a positive z component, which is the arrangement
// we want for A, B, C. If it's negative, then we've got it flipped around and
// should swap A and C.
if (crossProductZ(pointA, pointB, pointC) < 0.0f)
{
FinderPattern temp = pointA;
pointA = pointC;
pointC = temp;
}
patterns[0] = pointA;
patterns[1] = pointB;
patterns[2] = pointC;
}
/// <returns>
/// distance between two points
/// </returns>
public static float distance(FinderPattern pattern1, FinderPattern pattern2)
{
return ZXing.Common.Detector.MathUtils.distance(pattern1.x, pattern1.y, pattern2.x, pattern2.y);
}
internal virtual FinderPatternInfo find(IDictionary <DecodeHintType, object> hints)
{
bool tryHarder = hints != null && hints.ContainsKey(DecodeHintType.TRY_HARDER);
bool pureBarcode = hints != null && hints.ContainsKey(DecodeHintType.PURE_BARCODE);
int maxI = image.Height;
int maxJ = image.Width;
// We are looking for black/white/black/white/black modules in
// 1:1:3:1:1 ratio; this tracks the number of such modules seen so far
// Let's assume that the maximum version QR Code we support takes up 1/4 the height of the
// image, and then account for the center being 3 modules in size. This gives the smallest
// number of pixels the center could be, so skip this often. When trying harder, look for all
// QR versions regardless of how dense they are.
int iSkip = (3 * maxI) / (4 * MAX_MODULES);
if (iSkip < MIN_SKIP || tryHarder)
{
iSkip = MIN_SKIP;
}
bool done = false;
int[] stateCount = new int[5];
for (int i = iSkip - 1; i < maxI && !done; i += iSkip)
{
// Get a row of black/white values
stateCount[0] = 0;
stateCount[1] = 0;
stateCount[2] = 0;
stateCount[3] = 0;
stateCount[4] = 0;
int currentState = 0;
for (int j = 0; j < maxJ; j++)
{
if (image[j, i])
{
// Black pixel
if ((currentState & 1) == 1)
{
// Counting white pixels
currentState++;
}
stateCount[currentState]++;
}
else
{
// White pixel
if ((currentState & 1) == 0)
{
// Counting black pixels
if (currentState == 4)
{
// A winner?
if (foundPatternCross(stateCount))
{
// Yes
bool confirmed = handlePossibleCenter(stateCount, i, j, pureBarcode);
if (confirmed)
{
// Start examining every other line. Checking each line turned out to be too
// expensive and didn't improve performance.
iSkip = 2;
if (hasSkipped)
{
done = haveMultiplyConfirmedCenters();
}
else
{
int rowSkip = findRowSkip();
if (rowSkip > stateCount[2])
{
// Skip rows between row of lower confirmed center
// and top of presumed third confirmed center
// but back up a bit to get a full chance of detecting
// it, entire width of center of finder pattern
// Skip by rowSkip, but back off by stateCount[2] (size of last center
// of pattern we saw) to be conservative, and also back off by iSkip which
// is about to be re-added
i += rowSkip - stateCount[2] - iSkip;
j = maxJ - 1;
}
}
}
else
{
stateCount[0] = stateCount[2];
stateCount[1] = stateCount[3];
stateCount[2] = stateCount[4];
stateCount[3] = 1;
stateCount[4] = 0;
currentState = 3;
continue;
}
// Clear state to start looking again
currentState = 0;
stateCount[0] = 0;
stateCount[1] = 0;
stateCount[2] = 0;
stateCount[3] = 0;
stateCount[4] = 0;
}
else
{
// No, shift counts back by two
stateCount[0] = stateCount[2];
stateCount[1] = stateCount[3];
stateCount[2] = stateCount[4];
stateCount[3] = 1;
stateCount[4] = 0;
currentState = 3;
}
}
else
{
stateCount[++currentState]++;
}
}
else
{
// Counting white pixels
stateCount[currentState]++;
}
}
}
if (foundPatternCross(stateCount))
{
bool confirmed = handlePossibleCenter(stateCount, i, maxJ, pureBarcode);
if (confirmed)
{
iSkip = stateCount[0];
if (hasSkipped)
{
// Found a third one
done = haveMultiplyConfirmedCenters();
}
}
}
}
FinderPattern[] patternInfo = selectBestPatterns();
if (patternInfo == null)
{
return(null);
}
FinderPattern.orderBestPatterns(patternInfo);
return(new FinderPatternInfo(patternInfo));
}
/// <summary> <p>Computes the dimension (number of modules on a size) of the QR Code based on the position
/// of the finder patterns and estimated module size.</p>
/// </summary>
private static bool computeDimension(FinderPattern topLeft, FinderPattern topRight, FinderPattern bottomLeft, float moduleSize, out int dimension)
{
int tltrCentersDimension = MathUtils.round(FinderPattern.distance(topLeft, topRight) / moduleSize);
int tlblCentersDimension = MathUtils.round(FinderPattern.distance(topLeft, bottomLeft) / moduleSize);
dimension = ((tltrCentersDimension + tlblCentersDimension) >> 1) + 7;
switch (dimension & 0x03)
{
// mod 4
case 0:
dimension++;
break;
// 1? do nothing
case 2:
dimension--;
break;
case 3:
return true;
}
return true;
}
/// <returns> the 3 best {@link FinderPattern}s from our list of candidates. The "best" are
/// those have similar module size and form a shape closer to a isosceles right triangle.
/// </returns>
private FinderPattern[] selectBestPatterns()
{
int startSize = possibleCenters.Count;
if (startSize < 3)
{
// Couldn't find enough finder patterns
return(null);
}
possibleCenters.Sort(moduleComparator);
double distortion = Double.MaxValue;
double[] squares = new double[3];
FinderPattern[] bestPatterns = new FinderPattern[3];
for (int i = 0; i < possibleCenters.Count - 2; i++)
{
FinderPattern fpi = possibleCenters[i];
float minModuleSize = fpi.EstimatedModuleSize;
for (int j = i + 1; j < possibleCenters.Count - 1; j++)
{
FinderPattern fpj = possibleCenters[j];
double squares0 = squaredDistance(fpi, fpj);
for (int k = j + 1; k < possibleCenters.Count; k++)
{
FinderPattern fpk = possibleCenters[k];
float maxModuleSize = fpk.EstimatedModuleSize;
if (maxModuleSize > minModuleSize * 1.4f)
{
// module size is not similar
continue;
}
squares[0] = squares0;
squares[1] = squaredDistance(fpj, fpk);
squares[2] = squaredDistance(fpi, fpk);
Array.Sort(squares);
// a^2 + b^2 = c^2 (Pythagorean theorem), and a = b (isosceles triangle).
// Since any right triangle satisfies the formula c^2 - b^2 - a^2 = 0,
// we need to check both two equal sides separately.
// The value of |c^2 - 2 * b^2| + |c^2 - 2 * a^2| increases as dissimilarity
// from isosceles right triangle.
double d = Math.Abs(squares[2] - 2 * squares[1]) + Math.Abs(squares[2] - 2 * squares[0]);
if (d < distortion)
{
distortion = d;
bestPatterns[0] = fpi;
bestPatterns[1] = fpj;
bestPatterns[2] = fpk;
}
}
}
}
if (distortion == Double.MaxValue)
{
return(null);
}
return(bestPatterns);
}
/// <summary> <p>Estimates module size based on two finder patterns -- it uses
/// {@link #sizeOfBlackWhiteBlackRunBothWays(int, int, int, int)} to figure the
/// width of each, measuring along the axis between their centers.</p>
/// </summary>
private float calculateModuleSizeOneWay(FinderPattern pattern, FinderPattern otherPattern)
{
//UPGRADE_WARNING: Data types in Visual C# might be different. Verify the accuracy of narrowing conversions. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1042'"
float moduleSizeEst1 = sizeOfBlackWhiteBlackRunBothWays((int)pattern.X, (int)pattern.Y, (int)otherPattern.X, (int)otherPattern.Y);
//UPGRADE_WARNING: Data types in Visual C# might be different. Verify the accuracy of narrowing conversions. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1042'"
float moduleSizeEst2 = sizeOfBlackWhiteBlackRunBothWays((int)otherPattern.X, (int)otherPattern.Y, (int)pattern.X, (int)pattern.Y);
if (Single.IsNaN(moduleSizeEst1))
{
return moduleSizeEst2 / 7.0f;
}
if (Single.IsNaN(moduleSizeEst2))
{
return moduleSizeEst1 / 7.0f;
}
// Average them, and divide by 7 since we've counted the width of 3 black modules,
// and 1 white and 1 black module on either side. Ergo, divide sum by 14.
return (moduleSizeEst1 + moduleSizeEst2) / 14.0f;
}
/// <returns>
/// distance between two points
/// </returns>
public static float distance(FinderPattern pattern1, FinderPattern pattern2)
{
return(ZXing.Common.Detector.MathUtils.distance(pattern1.x, pattern1.y, pattern2.x, pattern2.y));
}