/**
* <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>
*/
private static int computeDimension(ResultPoint topLeft,
ResultPoint topRight,
ResultPoint bottomLeft,
float moduleSize)
{
int tltrCentersDimension = round(GenericResultPoint.distance(topLeft, topRight) / moduleSize);
int tlblCentersDimension = round(GenericResultPoint.distance(topLeft, bottomLeft) / moduleSize);
int dimension = ((tltrCentersDimension + tlblCentersDimension) >> 1) + 7;
switch (dimension & 0x03) // mod 4
{
case 0:
dimension++;
break;
// 1? do nothing
case 2:
dimension--;
break;
case 3:
throw new ReaderException();
}
return(dimension);
}
/**
* <p>Detects a Data Matrix Code in an image.</p>
*
* @return {@link DetectorResult} encapsulating results of detecting a QR Code
* @throws ReaderException if no Data Matrix Code can be found
*/
public DetectorResult detect()
{
if (!BlackPointEstimationMethod.TWO_D_SAMPLING.Equals(image.getLastEstimationMethod()))
{
image.estimateBlackPoint(BlackPointEstimationMethod.TWO_D_SAMPLING, 0);
}
int height = image.getHeight();
int width = image.getWidth();
int halfHeight = height >> 1;
int halfWidth = width >> 1;
int iSkip = Math.Max(1, height / (MAX_MODULES << 3));
int jSkip = Math.Max(1, width / (MAX_MODULES << 3));
int minI = 0;
int maxI = height;
int minJ = 0;
int maxJ = width;
ResultPoint pointA = findCornerFromCenter(halfHeight, -iSkip, minI, maxI, halfWidth, 0, minJ, maxJ, halfWidth >> 1);
minI = (int)pointA.getY() - 1;
ResultPoint pointB = findCornerFromCenter(halfHeight, 0, minI, maxI, halfWidth, -jSkip, minJ, maxJ, halfHeight >> 1);
minJ = (int)pointB.getX() - 1;
ResultPoint pointC = findCornerFromCenter(halfHeight, 0, minI, maxI, halfWidth, jSkip, minJ, maxJ, halfHeight >> 1);
maxJ = (int)pointC.getX() + 1;
ResultPoint pointD = findCornerFromCenter(halfHeight, iSkip, minI, maxI, halfWidth, 0, minJ, maxJ, halfWidth >> 1);
maxI = (int)pointD.getY() + 1;
// Go try to find point A again with better information -- might have been off at first.
pointA = findCornerFromCenter(halfHeight, -iSkip, minI, maxI, halfWidth, 0, minJ, maxJ, halfWidth >> 2);
// Point A and D are across the diagonal from one another,
// as are B and C. Figure out which are the solid black lines
// by counting transitions
System.Collections.ArrayList transitions = new System.Collections.ArrayList(4);
transitions.Add(transitionsBetween(pointA, pointB));
transitions.Add(transitionsBetween(pointA, pointC));
transitions.Add(transitionsBetween(pointB, pointD));
transitions.Add(transitionsBetween(pointC, pointD));
Collections.insertionSort(transitions, new ResultPointsAndTransitionsComparator());
// Sort by number of transitions. First two will be the two solid sides; last two
// will be the two alternating black/white sides
ResultPointsAndTransitions lSideOne = (ResultPointsAndTransitions)transitions[0];
ResultPointsAndTransitions lSideTwo = (ResultPointsAndTransitions)transitions[1];
// Figure out which point is their intersection by tallying up the number of times we see the
// endpoints in the four endpoints. One will show up twice.
System.Collections.Hashtable pointCount = new System.Collections.Hashtable();
increment(pointCount, lSideOne.getFrom());
increment(pointCount, lSideOne.getTo());
increment(pointCount, lSideTwo.getFrom());
increment(pointCount, lSideTwo.getTo());
ResultPoint maybeTopLeft = null;
ResultPoint bottomLeft = null;
ResultPoint maybeBottomRight = null;
System.Collections.IEnumerator points = pointCount.GetEnumerator();
while (points.MoveNext())
{
ResultPoint point = (ResultPoint)points.Current;
int value = (int)pointCount[point];
if (value == 2)
{
bottomLeft = point; // this is definitely the bottom left, then -- end of two L sides
}
else
{
// Otherwise it's either top left or bottom right -- just assign the two arbitrarily now
if (maybeTopLeft == null)
{
maybeTopLeft = point;
}
else
{
maybeBottomRight = point;
}
}
}
if (maybeTopLeft == null || bottomLeft == null || maybeBottomRight == null)
{
throw new ReaderException();
}
// Bottom left is correct but top left and bottom right might be switched
ResultPoint[] corners = { maybeTopLeft, bottomLeft, maybeBottomRight };
// Use the dot product trick to sort them out
GenericResultPoint.orderBestPatterns(corners);
// Now we know which is which:
ResultPoint bottomRight = corners[0];
bottomLeft = corners[1];
ResultPoint topLeft = corners[2];
// Which point didn't we find in relation to the "L" sides? that's the top right corner
ResultPoint topRight;
if (!pointCount.ContainsKey(pointA))
{
topRight = pointA;
}
else if (!pointCount.ContainsKey(pointB))
{
topRight = pointB;
}
else if (!pointCount.ContainsKey(pointC))
{
topRight = pointC;
}
else
{
topRight = pointD;
}
// Next determine the dimension by tracing along the top or right side and counting black/white
// transitions. Since we start inside a black module, we should see a number of transitions
// equal to 1 less than the code dimension. Well, actually 2 less, because we are going to
// end on a black module:
// The top right point is actually the corner of a module, which is one of the two black modules
// adjacent to the white module at the top right. Tracing to that corner from either the top left
// or bottom right should work here, but, one will be more reliable since it's traced straight
// up or across, rather than at a slight angle. We use dot products to figure out which is
// better to use:
int dimension;
if (GenericResultPoint.crossProductZ(bottomLeft, bottomRight, topRight) <
GenericResultPoint.crossProductZ(topRight, topLeft, bottomLeft))
{
dimension = transitionsBetween(topLeft, topRight).getTransitions();
}
else
{
dimension = transitionsBetween(bottomRight, topRight).getTransitions();
}
dimension += 2;
BitMatrix bits = sampleGrid(image, topLeft, bottomLeft, bottomRight, dimension);
return(new DetectorResult(bits, new ResultPoint[] { pointA, pointB, pointC, pointD }));
}
public FinderPatternInfo find(System.Collections.Hashtable hints)
{
bool tryHarder = hints != null && hints.ContainsKey(DecodeHintType.TRY_HARDER);
int maxI = image.getHeight();
int maxJ = image.getWidth();
// 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 = (int)(maxI / (MAX_MODULES * 4.0f) * 3);
if (iSkip < MIN_SKIP || tryHarder)
{
iSkip = MIN_SKIP;
}
bool done = false;
int[] stateCount = new int[5];
BitArray blackRow = new BitArray(maxJ);
for (int i = iSkip - 1; i < maxI && !done; i += iSkip)
{
// Get a row of black/white values
blackRow = image.getBlackRow(i, blackRow, 0, maxJ);
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 (blackRow.get(j))
{
// 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);
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 = haveMulitplyConfirmedCenters();
}
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
{
// Advance to next black pixel
do
{
j++;
} while (j < maxJ && !blackRow.get(j));
j--; // back up to that last white pixel
}
// 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);
if (confirmed)
{
iSkip = stateCount[0];
if (hasSkipped)
{
// Found a third one
done = haveMulitplyConfirmedCenters();
}
}
}
}
FinderPattern[] patternInfo = selectBestPatterns();
GenericResultPoint.orderBestPatterns(patternInfo);
return(new FinderPatternInfo(patternInfo));
}
