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Diffstat (limited to 'libraries/zxing/src/com/google/zxing/common/detector/MonochromeRectangleDetector.java')
| -rw-r--r-- | libraries/zxing/src/com/google/zxing/common/detector/MonochromeRectangleDetector.java | 209 |
1 files changed, 209 insertions, 0 deletions
diff --git a/libraries/zxing/src/com/google/zxing/common/detector/MonochromeRectangleDetector.java b/libraries/zxing/src/com/google/zxing/common/detector/MonochromeRectangleDetector.java new file mode 100644 index 000000000..950a22364 --- /dev/null +++ b/libraries/zxing/src/com/google/zxing/common/detector/MonochromeRectangleDetector.java @@ -0,0 +1,209 @@ +/* + * 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.NotFoundException; +import com.google.zxing.ResultPoint; +import com.google.zxing.common.BitMatrix; + +/** + * <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 BitMatrix image; + + public MonochromeRectangleDetector(BitMatrix 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 NotFoundException if no Data Matrix Code can be found + */ + public ResultPoint[] detect() throws NotFoundException { + int height = image.getHeight(); + int width = image.getWidth(); + int halfHeight = height >> 1; + int halfWidth = width >> 1; + int deltaY = Math.max(1, height / (MAX_MODULES << 3)); + int deltaX = Math.max(1, width / (MAX_MODULES << 3)); + + int top = 0; + int bottom = height; + int left = 0; + int right = width; + ResultPoint pointA = findCornerFromCenter(halfWidth, 0, left, right, + halfHeight, -deltaY, top, bottom, halfWidth >> 1); + top = (int) pointA.getY() - 1; + ResultPoint pointB = findCornerFromCenter(halfWidth, -deltaX, left, right, + halfHeight, 0, top, bottom, halfHeight >> 1); + left = (int) pointB.getX() - 1; + ResultPoint pointC = findCornerFromCenter(halfWidth, deltaX, left, right, + halfHeight, 0, top, bottom, halfHeight >> 1); + right = (int) pointC.getX() + 1; + ResultPoint pointD = findCornerFromCenter(halfWidth, 0, left, right, + halfHeight, deltaY, top, bottom, halfWidth >> 1); + bottom = (int) pointD.getY() + 1; + + // Go try to find point A again with better information -- might have been off at first. + pointA = findCornerFromCenter(halfWidth, 0, left, right, + halfHeight, -deltaY, top, bottom, 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 centerX center's x component (horizontal) + * @param deltaX same as deltaY but change in x per step instead + * @param left minimum value of x + * @param right maximum value of x + * @param centerY center's y component (vertical) + * @param deltaY change in y per step. If scanning up this is negative; down, positive; + * left or right, 0 + * @param top minimum value of y to search through (meaningless when di == 0) + * @param bottom maximum value of y + * @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 NotFoundException if such a point cannot be found + */ + private ResultPoint findCornerFromCenter(int centerX, int deltaX, int left, int right, + int centerY, int deltaY, int top, int bottom, int maxWhiteRun) throws NotFoundException { + int[] lastRange = null; + for (int y = centerY, x = centerX; + y < bottom && y >= top && x < right && x >= left; + y += deltaY, x += deltaX) { + int[] range; + if (deltaX == 0) { + // horizontal slices, up and down + range = blackWhiteRange(y, maxWhiteRun, left, right, true); + } else { + // vertical slices, left and right + range = blackWhiteRange(x, maxWhiteRun, top, bottom, false); + } + if (range == null) { + if (lastRange == null) { + throw NotFoundException.getNotFoundInstance(); + } + // lastRange was found + if (deltaX == 0) { + int lastY = y - deltaY; + if (lastRange[0] < centerX) { + if (lastRange[1] > centerX) { + // straddle, choose one or the other based on direction + return new ResultPoint(deltaY > 0 ? lastRange[0] : lastRange[1], lastY); + } + return new ResultPoint(lastRange[0], lastY); + } else { + return new ResultPoint(lastRange[1], lastY); + } + } else { + int lastX = x - deltaX; + if (lastRange[0] < centerY) { + if (lastRange[1] > centerY) { + return new ResultPoint(lastX, deltaX < 0 ? lastRange[0] : lastRange[1]); + } + return new ResultPoint(lastX, lastRange[0]); + } else { + return new ResultPoint(lastX, lastRange[1]); + } + } + } + lastRange = range; + } + throw NotFoundException.getNotFoundInstance(); + } + + /** + * 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 column, 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) >> 1; + + // Scan left/up first + int start = center; + while (start >= minDim) { + if (horizontal ? image.get(start, fixedDimension) : image.get(fixedDimension, start)) { + start--; + } else { + int whiteRunStart = start; + do { + start--; + } while (start >= minDim && !(horizontal ? image.get(start, fixedDimension) : + image.get(fixedDimension, start))); + int whiteRunSize = whiteRunStart - start; + if (start < minDim || whiteRunSize > maxWhiteRun) { + start = whiteRunStart; + break; + } + } + } + start++; + + // Then try right/down + int end = center; + while (end < maxDim) { + if (horizontal ? image.get(end, fixedDimension) : image.get(fixedDimension, end)) { + end++; + } else { + int whiteRunStart = end; + do { + end++; + } while (end < maxDim && !(horizontal ? image.get(end, fixedDimension) : + image.get(fixedDimension, end))); + int whiteRunSize = end - whiteRunStart; + if (end >= maxDim || whiteRunSize > maxWhiteRun) { + end = whiteRunStart; + break; + } + } + } + end--; + + return end > start ? new int[]{start, end} : null; + } + +}
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