--- /dev/null
+/*\r
+* Copyright 2007 ZXing authors\r
+*\r
+* Licensed under the Apache License, Version 2.0 (the "License");\r
+* you may not use this file except in compliance with the License.\r
+* You may obtain a copy of the License at\r
+*\r
+* http://www.apache.org/licenses/LICENSE-2.0\r
+*\r
+* Unless required by applicable law or agreed to in writing, software\r
+* distributed under the License is distributed on an "AS IS" BASIS,\r
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.\r
+* See the License for the specific language governing permissions and\r
+* limitations under the License.\r
+*/\r
+using System;\r
+using com.google.zxing;\r
+using com.google.zxing.common;\r
+\r
+namespace com.google.zxing.qrcode.detector\r
+{\r
+ public sealed class AlignmentPatternFinder\r
+ { \r
+ private MonochromeBitmapSource image;\r
+ private System.Collections.ArrayList possibleCenters;\r
+ private int startX;\r
+ private int startY;\r
+ private int width;\r
+ private int height;\r
+ private float moduleSize;\r
+ private int[] crossCheckStateCount;\r
+\r
+ /**\r
+ * <p>Creates a finder that will look in a portion of the whole image.</p>\r
+ *\r
+ * @param image image to search\r
+ * @param startX left column from which to start searching\r
+ * @param startY top row from which to start searching\r
+ * @param width width of region to search\r
+ * @param height height of region to search\r
+ * @param moduleSize estimated module size so far\r
+ */\r
+ public AlignmentPatternFinder(MonochromeBitmapSource image,\r
+ int startX,\r
+ int startY,\r
+ int width,\r
+ int height,\r
+ float moduleSize) {\r
+ this.image = image;\r
+ this.possibleCenters = new System.Collections.ArrayList(5);\r
+ this.startX = startX;\r
+ this.startY = startY;\r
+ this.width = width;\r
+ this.height = height;\r
+ this.moduleSize = moduleSize;\r
+ this.crossCheckStateCount = new int[3];\r
+ }\r
+\r
+ /**\r
+ * <p>This method attempts to find the bottom-right alignment pattern in the image. It is a bit messy since\r
+ * it's pretty performance-critical and so is written to be fast foremost.</p>\r
+ *\r
+ * @return {@link AlignmentPattern} if found\r
+ * @throws ReaderException if not found\r
+ */\r
+ public AlignmentPattern find() {\r
+ int startX = this.startX;\r
+ int height = this.height;\r
+ int maxJ = startX + width;\r
+ int middleI = startY + (height >> 1);\r
+ BitArray luminanceRow = new BitArray(width);\r
+ // We are looking for black/white/black modules in 1:1:1 ratio;\r
+ // this tracks the number of black/white/black modules seen so far\r
+ int[] stateCount = new int[3];\r
+ for (int iGen = 0; iGen < height; iGen++) {\r
+ // Search from middle outwards\r
+ int i = middleI + ((iGen & 0x01) == 0 ? ((iGen + 1) >> 1) : -((iGen + 1) >> 1));\r
+ image.getBlackRow(i, luminanceRow, startX, width);\r
+ stateCount[0] = 0;\r
+ stateCount[1] = 0;\r
+ stateCount[2] = 0;\r
+ int j = startX;\r
+ // Burn off leading white pixels before anything else; if we start in the middle of\r
+ // a white run, it doesn't make sense to count its length, since we don't know if the\r
+ // white run continued to the left of the start point\r
+ while (j < maxJ && !luminanceRow.get(j - startX)) {\r
+ j++;\r
+ }\r
+ int currentState = 0;\r
+ while (j < maxJ) {\r
+ if (luminanceRow.get(j - startX)) {\r
+ // Black pixel\r
+ if (currentState == 1) { // Counting black pixels\r
+ stateCount[currentState]++;\r
+ } else { // Counting white pixels\r
+ if (currentState == 2) { // A winner?\r
+ if (foundPatternCross(stateCount)) { // Yes\r
+ AlignmentPattern confirmed = handlePossibleCenter(stateCount, i, j);\r
+ if (confirmed != null) {\r
+ return confirmed;\r
+ }\r
+ }\r
+ stateCount[0] = stateCount[2];\r
+ stateCount[1] = 1;\r
+ stateCount[2] = 0;\r
+ currentState = 1;\r
+ } else {\r
+ stateCount[++currentState]++;\r
+ }\r
+ }\r
+ } else { // White pixel\r
+ if (currentState == 1) { // Counting black pixels\r
+ currentState++;\r
+ }\r
+ stateCount[currentState]++;\r
+ }\r
+ j++;\r
+ }\r
+ if (foundPatternCross(stateCount)) {\r
+ AlignmentPattern confirmed = handlePossibleCenter(stateCount, i, maxJ);\r
+ if (confirmed != null) {\r
+ return confirmed;\r
+ }\r
+ }\r
+\r
+ }\r
+\r
+ // Hmm, nothing we saw was observed and confirmed twice. If we had\r
+ // any guess at all, return it.\r
+ if (!(possibleCenters.Count==0)) {\r
+ return (AlignmentPattern) possibleCenters[0];\r
+ }\r
+\r
+ throw new ReaderException();\r
+ }\r
+\r
+ /**\r
+ * Given a count of black/white/black pixels just seen and an end position,\r
+ * figures the location of the center of this black/white/black run.\r
+ */\r
+ private static float centerFromEnd(int[] stateCount, int end) {\r
+ return (float) (end - stateCount[2]) - stateCount[1] / 2.0f;\r
+ }\r
+\r
+ /**\r
+ * @param stateCount count of black/white/black pixels just read\r
+ * @return true iff the proportions of the counts is close enough to the 1/1/1 ratios\r
+ * used by alignment patterns to be considered a match\r
+ */\r
+ private bool foundPatternCross(int[] stateCount) {\r
+ float moduleSize = this.moduleSize;\r
+ float maxVariance = moduleSize / 2.0f;\r
+ for (int i = 0; i < 3; i++) {\r
+ if (Math.Abs(moduleSize - stateCount[i]) >= maxVariance) {\r
+ return false;\r
+ }\r
+ }\r
+ return true;\r
+ }\r
+\r
+ /**\r
+ * <p>After a horizontal scan finds a potential alignment pattern, this method\r
+ * "cross-checks" by scanning down vertically through the center of the possible\r
+ * alignment pattern to see if the same proportion is detected.</p>\r
+ *\r
+ * @param startI row where an alignment pattern was detected\r
+ * @param centerJ center of the section that appears to cross an alignment pattern\r
+ * @param maxCount maximum reasonable number of modules that should be\r
+ * observed in any reading state, based on the results of the horizontal scan\r
+ * @return vertical center of alignment pattern, or {@link Float#NaN} if not found\r
+ */\r
+ private float crossCheckVertical(int startI, int centerJ, int maxCount, int originalStateCountTotal) {\r
+ MonochromeBitmapSource image = this.image;\r
+\r
+ int maxI = image.getHeight();\r
+ int[] stateCount = crossCheckStateCount;\r
+ stateCount[0] = 0;\r
+ stateCount[1] = 0;\r
+ stateCount[2] = 0;\r
+\r
+ // Start counting up from center\r
+ int i = startI;\r
+ while (i >= 0 && image.isBlack(centerJ, i) && stateCount[1] <= maxCount) {\r
+ stateCount[1]++;\r
+ i--;\r
+ }\r
+ // If already too many modules in this state or ran off the edge:\r
+ if (i < 0 || stateCount[1] > maxCount) {\r
+ return float.NaN;\r
+ }\r
+ while (i >= 0 && !image.isBlack(centerJ, i) && stateCount[0] <= maxCount) {\r
+ stateCount[0]++;\r
+ i--;\r
+ }\r
+ if (stateCount[0] > maxCount) {\r
+ return float.NaN;\r
+ }\r
+\r
+ // Now also count down from center\r
+ i = startI + 1;\r
+ while (i < maxI && image.isBlack(centerJ, i) && stateCount[1] <= maxCount) {\r
+ stateCount[1]++;\r
+ i++;\r
+ }\r
+ if (i == maxI || stateCount[1] > maxCount) {\r
+ return float.NaN;\r
+ }\r
+ while (i < maxI && !image.isBlack(centerJ, i) && stateCount[2] <= maxCount) {\r
+ stateCount[2]++;\r
+ i++;\r
+ }\r
+ if (stateCount[2] > maxCount) {\r
+ return float.NaN;\r
+ }\r
+\r
+ int stateCountTotal = stateCount[0] + stateCount[1] + stateCount[2];\r
+ if (5 * Math.Abs(stateCountTotal - originalStateCountTotal) >= originalStateCountTotal) {\r
+ return float.NaN;\r
+ }\r
+\r
+ return foundPatternCross(stateCount) ? centerFromEnd(stateCount, i) : float.NaN;\r
+ }\r
+\r
+ /**\r
+ * <p>This is called when a horizontal scan finds a possible alignment pattern. It will\r
+ * cross check with a vertical scan, and if successful, will see if this pattern had been\r
+ * found on a previous horizontal scan. If so, we consider it confirmed and conclude we have\r
+ * found the alignment pattern.</p>\r
+ *\r
+ * @param stateCount reading state module counts from horizontal scan\r
+ * @param i row where alignment pattern may be found\r
+ * @param j end of possible alignment pattern in row\r
+ * @return {@link AlignmentPattern} if we have found the same pattern twice, or null if not\r
+ */\r
+ private AlignmentPattern handlePossibleCenter(int[] stateCount, int i, int j) {\r
+ int stateCountTotal = stateCount[0] + stateCount[1] + stateCount[2];\r
+ float centerJ = centerFromEnd(stateCount, j);\r
+ float centerI = crossCheckVertical(i, (int) centerJ, 2 * stateCount[1], stateCountTotal);\r
+ if (!Single.IsNaN(centerI))\r
+ {\r
+ float estimatedModuleSize = (float) (stateCount[0] + stateCount[1] + stateCount[2]) / 3.0f;\r
+ int max = possibleCenters.Count;\r
+ for (int index = 0; index < max; index++) {\r
+ AlignmentPattern center = (AlignmentPattern) possibleCenters[index];\r
+ // Look for about the same center and module size:\r
+ if (center.aboutEquals(estimatedModuleSize, centerI, centerJ)) {\r
+ return new AlignmentPattern(centerJ, centerI, estimatedModuleSize);\r
+ }\r
+ }\r
+ // Hadn't found this before; save it\r
+ possibleCenters.Add(new AlignmentPattern(centerJ, centerI, estimatedModuleSize));\r
+ }\r
+ return null;\r
+ }\r
+ \r
+ \r
+ }\r
+}
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projects / zxing.git / blobdiff