+ public DetectorResult detect() throws ReaderException {
+
+ 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 << 2));
+ int jSkip = Math.max(1, width / (MAX_MODULES << 2));
+
+ int minI = 0;
+ int maxI = height;
+ int minJ = 0;
+ int maxJ = width;
+ ResultPoint pointA = findCornerFromCenter(halfHeight, -iSkip, minI, maxI, halfWidth, 0, minJ, maxJ, halfWidth >> 2);
+ minI = (int) pointA.getY() - 1;
+ ResultPoint pointB = findCornerFromCenter(halfHeight, 0, minI, maxI, halfWidth, -jSkip, minJ, maxJ, halfHeight >> 2);
+ minJ = (int) pointB.getX() - 1;
+ ResultPoint pointC = findCornerFromCenter(halfHeight, 0, minI, maxI, halfWidth, jSkip, minJ, maxJ, halfHeight >> 2);
+ maxJ = (int) pointC.getX() + 1;
+ ResultPoint pointD = findCornerFromCenter(halfHeight, iSkip, minI, maxI, halfWidth, 0, minJ, maxJ, halfWidth >> 2);
+ 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
+ Vector transitions = new Vector(4);
+ transitions.addElement(transitionsBetween(pointA, pointB));
+ transitions.addElement(transitionsBetween(pointA, pointC));
+ transitions.addElement(transitionsBetween(pointB, pointD));
+ transitions.addElement(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.elementAt(0);
+ ResultPointsAndTransitions lSideTwo = (ResultPointsAndTransitions) transitions.elementAt(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.
+ Hashtable pointCount = new 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;
+ Enumeration points = pointCount.keys();
+ while (points.hasMoreElements()) {
+ ResultPoint point = (ResultPoint) points.nextElement();
+ Integer value = (Integer) pointCount.get(point);
+ if (value.intValue() == 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;
+ }
+ }
+ }
+
+ // Bottom left is correct but top left and bottom right might be switched
+ ResultPoint[] corners = new ResultPoint[] { 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});
+ }
+
+ /**
+ * Attempts to locate a corner of the barcode by scanning up, down, left or right from a center
+ * point which should be within the barcode.
+ *
+ * @param centerI center's i componennt (vertical)
+ * @param di change in i per step. If scanning up this is negative; down, positive; left or right, 0
+ * @param minI minimum value of i to search through (meaningless when di == 0)
+ * @param maxI maximum value of i
+ * @param centerJ center's j component (horizontal)
+ * @param dj same as di but change in j per step instead
+ * @param minJ see minI
+ * @param maxJ see minJ
+ * @param maxWhiteRun maximum run of white pixels that can still be considered to be within
+ * the barcode
+ * @return a {@link ResultPoint} encapsulating the corner that was found
+ * @throws ReaderException if such a point cannot be found
+ */
+ private ResultPoint findCornerFromCenter(int centerI, int di, int minI, int maxI,
+ int centerJ, int dj, int minJ, int maxJ,
+ int maxWhiteRun) throws ReaderException {
+ int[] lastRange = null;
+ for (int i = centerI, j = centerJ;
+ i < maxI && i >= minI && j < maxJ && j >= minJ;
+ i += di, j += dj) {
+ int[] range;
+ if (dj == 0) {
+ // horizontal slices, up and down
+ range = blackWhiteRange(i, maxWhiteRun, minJ, maxJ, true);
+ } else {
+ // vertical slices, left and right
+ range = blackWhiteRange(j, maxWhiteRun, minI, maxI, false);
+ }
+ if (range == null) {
+ if (lastRange == null) {
+ throw new ReaderException("Center of image not within barcode");
+ }
+ // lastRange was found
+ if (dj == 0) {
+ int lastI = i - di;
+ if (lastRange[0] < centerJ) {
+ if (lastRange[1] > centerJ) {
+ // straddle, choose one or the other based on direction
+ return new GenericResultPoint(di > 0 ? lastRange[0] : lastRange[1], lastI);
+ }
+ return new GenericResultPoint(lastRange[0], lastI);
+ } else {
+ return new GenericResultPoint(lastRange[1], lastI);
+ }
+ } else {
+ int lastJ = j - dj;
+ if (lastRange[0] < centerI) {
+ if (lastRange[1] > centerI) {
+ return new GenericResultPoint(lastJ, dj < 0 ? lastRange[0] : lastRange[1]);
+ }
+ return new GenericResultPoint(lastJ, lastRange[0]);
+ } else {
+ return new GenericResultPoint(lastJ, lastRange[1]);
+ }
+ }
+ }
+ lastRange = range;
+ }
+ throw new ReaderException("Couldn't find an end to barcode");
+ }
+
+ /**
+ * Increments the Integer associated with a key by one.
+ */
+ private static void increment(Hashtable table, ResultPoint key) {
+ Integer value = (Integer) table.get(key);
+ table.put(key, value == null ? INTEGERS[1] : INTEGERS[value.intValue() + 1]);