--- /dev/null
+/*
+ * Copyright 2009 ZXing authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.zxing.common.detector;
+
+import com.google.zxing.MonochromeBitmapSource;
+import com.google.zxing.ReaderException;
+import com.google.zxing.ResultPoint;
+import com.google.zxing.BlackPointEstimationMethod;
+import com.google.zxing.common.BitArray;
+import com.google.zxing.common.GenericResultPoint;
+
+/**
+ * <p>A somewhat generic detector that looks for a barcode-like rectangular region within an image.
+ * It looks within a mostly white region of an image for a region of black and white, but mostly black.
+ * It returns the four corners of the region, as best it can determine.</p>
+ *
+ * @author Sean Owen
+ */
+public final class MonochromeRectangleDetector {
+
+ private static final int MAX_MODULES = 32;
+
+ private final MonochromeBitmapSource image;
+
+ public MonochromeRectangleDetector(MonochromeBitmapSource image) {
+ this.image = image;
+ }
+
+ /**
+ * <p>Detects a rectangular region of black and white -- mostly black -- with a region of mostly
+ * white, in an image.</p>
+ *
+ * @return {@link ResultPoint[]} describing the corners of the rectangular region. The first and last points
+ * are opposed on the diagonal, as are the second and third. The first point will be the topmost point and
+ * the last, the bottommost. The second point will be leftmost and the third, the rightmost
+ * @throws ReaderException if no Data Matrix Code can be found
+ */
+ public ResultPoint[] 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 << 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);
+
+ return 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 com.google.zxing.ResultPoint} encapsulating the corner that was found
+ * @throws com.google.zxing.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 ReaderException.getInstance();
+ }
+ // 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 ReaderException.getInstance();
+ }
+
+ /**
+ * Computes the start and end of a region of pixels, either horizontally or vertically, that could be
+ * part of a Data Matrix barcode.
+ *
+ * @param fixedDimension if scanning horizontally, this is the row (the fixed vertical location) where
+ * we are scanning. If scanning vertically it's the colummn, the fixed horizontal location
+ * @param maxWhiteRun largest run of white pixels that can still be considered part of the barcode region
+ * @param minDim minimum pixel location, horizontally or vertically, to consider
+ * @param maxDim maximum pixel location, horizontally or vertically, to consider
+ * @param horizontal if true, we're scanning left-right, instead of up-down
+ * @return int[] with start and end of found range, or null if no such range is found (e.g. only white was found)
+ */
+ private int[] blackWhiteRange(int fixedDimension, int maxWhiteRun, int minDim, int maxDim, boolean horizontal) {
+
+ int center = (minDim + maxDim) / 2;
+
+ BitArray rowOrColumn = horizontal ? image.getBlackRow(fixedDimension, null, 0, image.getWidth())
+ : image.getBlackColumn(fixedDimension, null, 0, image.getHeight());
+
+ // Scan left/up first
+ int start = center;
+ while (start >= minDim) {
+ if (rowOrColumn.get(start)) {
+ start--;
+ } else {
+ int whiteRunStart = start;
+ do {
+ start--;
+ } while (start >= minDim && !rowOrColumn.get(start));
+ int whiteRunSize = whiteRunStart - start;
+ if (start < minDim || whiteRunSize > maxWhiteRun) {
+ start = whiteRunStart + 1; // back up
+ break;
+ }
+ }
+ }
+ start++;
+
+ // Then try right/down
+ int end = center;
+ while (end < maxDim) {
+ if (rowOrColumn.get(end)) {
+ end++;
+ } else {
+ int whiteRunStart = end;
+ do {
+ end++;
+ } while (end < maxDim && !rowOrColumn.get(end));
+ int whiteRunSize = end - whiteRunStart;
+ if (end >= maxDim || whiteRunSize > maxWhiteRun) {
+ end = whiteRunStart - 1;
+ break;
+ }
+ }
+ }
+ end--;
+
+ if (end > start) {
+ return new int[] { start, end };
+ } else {
+ return null;
+ }
+ }
+
+}
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projects / zxing.git / blobdiff