/*
- * Copyright 2008 Google Inc.
+ * Copyright 2008 ZXing authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
package com.google.zxing.oned;
import com.google.zxing.BlackPointEstimationMethod;
+import com.google.zxing.DecodeHintType;
import com.google.zxing.MonochromeBitmapSource;
import com.google.zxing.ReaderException;
import com.google.zxing.Result;
+import com.google.zxing.ResultMetadataType;
+import com.google.zxing.ResultPoint;
import com.google.zxing.common.BitArray;
import java.util.Hashtable;
* of one-dimensional barcodes.</p>
*
* @author dswitkin@google.com (Daniel Switkin)
- * @author srowen@google.com (Sean Owen)
+ * @author Sean Owen
*/
public abstract class AbstractOneDReader implements OneDReader {
+ private static final int INTEGER_MATH_SHIFT = 8;
+ static final int PATTERN_MATCH_RESULT_SCALE_FACTOR = 1 << INTEGER_MATH_SHIFT;
+
public final Result decode(MonochromeBitmapSource image) throws ReaderException {
return decode(image, null);
}
public final Result decode(MonochromeBitmapSource image, Hashtable hints) throws ReaderException {
+ try {
+ return doDecode(image, hints);
+ } catch (ReaderException re) {
+ boolean tryHarder = hints != null && hints.containsKey(DecodeHintType.TRY_HARDER);
+ if (tryHarder && image.isRotateSupported()) {
+ MonochromeBitmapSource rotatedImage = image.rotateCounterClockwise();
+ Result result = doDecode(rotatedImage, hints);
+ // Record that we found it rotated 90 degrees CCW / 270 degrees CW
+ Hashtable metadata = result.getResultMetadata();
+ int orientation = 270;
+ if (metadata != null && metadata.containsKey(ResultMetadataType.ORIENTATION)) {
+ // But if we found it reversed in doDecode(), add in that result here:
+ orientation = (orientation + ((Integer) metadata.get(ResultMetadataType.ORIENTATION)).intValue()) % 360;
+ }
+ result.putMetadata(ResultMetadataType.ORIENTATION, new Integer(orientation));
+ return result;
+ } else {
+ throw re;
+ }
+ }
+ }
+ /**
+ * We're going to examine rows from the middle outward, searching alternately above and below the
+ * middle, and farther out each time. rowStep is the number of rows between each successive
+ * attempt above and below the middle. So we'd scan row middle, then middle - rowStep, then
+ * middle + rowStep, then middle - (2 * rowStep), etc.
+ * rowStep is bigger as the image is taller, but is always at least 1. We've somewhat arbitrarily
+ * decided that moving up and down by about 1/16 of the image is pretty good; we try more of the
+ * image if "trying harder".
+ *
+ * @param image The image to decode
+ * @param hints Any hints that were requested
+ * @return The contents of the decoded barcode
+ * @throws ReaderException Any spontaneous errors which occur
+ */
+ private Result doDecode(MonochromeBitmapSource image, Hashtable hints) throws ReaderException {
int width = image.getWidth();
int height = image.getHeight();
-
BitArray row = new BitArray(width);
- // We're going to examine rows from the middle outward, searching alternately above and below the middle,
- // and farther out each time. rowStep is the number of rows between each successive attempt above and below
- // the middle. So we'd scan row middle, then middle - rowStep, then middle + rowStep,
- // then middle - 2*rowStep, etc.
- // rowStep is bigger as the image is taller, but is always at least 1. We've somewhat arbitrarily decided
- // that moving up and down by about 1/16 of the image is pretty good.
int middle = height >> 1;
- int rowStep = Math.max(1, height >> 5);
- for (int x = 0; x < 11; x++) {
+ boolean tryHarder = hints != null && hints.containsKey(DecodeHintType.TRY_HARDER);
+ int rowStep = Math.max(1, height >> (tryHarder ? 7 : 4));
+ int maxLines;
+ if (tryHarder) {
+ maxLines = height; // Look at the whole image, not just the center
+ } else {
+ maxLines = 9; // Nine rows spaced 1/16 apart is roughly the middle half of the image
+ }
+
+ for (int x = 0; x < maxLines; x++) {
+ // Scanning from the middle out. Determine which row we're looking at next:
int rowStepsAboveOrBelow = (x + 1) >> 1;
boolean isAbove = (x & 0x01) == 0; // i.e. is x even?
int rowNumber = middle + rowStep * (isAbove ? rowStepsAboveOrBelow : -rowStepsAboveOrBelow);
+ if (rowNumber < 0 || rowNumber >= height) {
+ // Oops, if we run off the top or bottom, stop
+ break;
+ }
- image.estimateBlackPoint(BlackPointEstimationMethod.ROW_SAMPLING, rowNumber);
- image.getBlackRow(rowNumber, row, 0, width);
-
+ // Estimate black point for this row and load it:
try {
- return decodeRow(rowNumber, row);
+ image.estimateBlackPoint(BlackPointEstimationMethod.ROW_SAMPLING, rowNumber);
} catch (ReaderException re) {
- // TODO re-enable this in a "try harder" mode?
- //row.reverse(); // try scanning the row backwards
- //try {
- // return decodeRow(rowNumber, row);
- //} catch (ReaderException re2) {
- // continue
- //}
+ continue;
}
+ row = image.getBlackRow(rowNumber, row, 0, width);
+ // While we have the image data in a BitArray, it's fairly cheap to reverse it in place to
+ // handle decoding upside down barcodes.
+ for (int attempt = 0; attempt < 2; attempt++) {
+ if (attempt == 1) { // trying again?
+ row.reverse(); // reverse the row and continue
+ }
+ try {
+ // Look for a barcode
+ Result result = decodeRow(rowNumber, row, hints);
+ // We found our barcode
+ if (attempt == 1) {
+ // But it was upside down, so note that
+ result.putMetadata(ResultMetadataType.ORIENTATION, new Integer(180));
+ // And remember to flip the result points horizontally.
+ ResultPoint[] points = result.getResultPoints();
+ points[0] = new ResultPoint(width - points[0].getX() - 1, points[0].getY());
+ points[1] = new ResultPoint(width - points[1].getX() - 1, points[1].getY());
+ }
+ return result;
+ } catch (ReaderException re) {
+ // continue -- just couldn't decode this row
+ }
+ }
}
- throw new ReaderException("No barcode found");
+ throw ReaderException.getInstance();
}
- protected static void recordPattern(BitArray row, int start, int[] counters) throws ReaderException {
- for (int i = 0; i < counters.length; i++) {
+ /**
+ * Records the size of successive runs of white and black pixels in a row, starting at a given point.
+ * The values are recorded in the given array, and the number of runs recorded is equal to the size
+ * of the array. If the row starts on a white pixel at the given start point, then the first count
+ * recorded is the run of white pixels starting from that point; likewise it is the count of a run
+ * of black pixels if the row begin on a black pixels at that point.
+ *
+ * @param row row to count from
+ * @param start offset into row to start at
+ * @param counters array into which to record counts
+ * @throws ReaderException if counters cannot be filled entirely from row before running out of pixels
+ */
+ static void recordPattern(BitArray row, int start, int[] counters) throws ReaderException {
+ int numCounters = counters.length;
+ for (int i = 0; i < numCounters; i++) {
counters[i] = 0;
}
int end = row.getSize();
if (start >= end) {
- throw new ReaderException("Couldn't fully read a pattern");
+ throw ReaderException.getInstance();
}
boolean isWhite = !row.get(start);
int counterPosition = 0;
int i = start;
while (i < end) {
boolean pixel = row.get(i);
- if ((!pixel && isWhite) || (pixel && !isWhite)) {
+ if (pixel ^ isWhite) { // that is, exactly one is true
counters[counterPosition]++;
} else {
counterPosition++;
- if (counterPosition == counters.length) {
+ if (counterPosition == numCounters) {
break;
} else {
counters[counterPosition] = 1;
- isWhite = !isWhite;
+ isWhite ^= true; // isWhite = !isWhite; Is this too clever? shorter byte code, no conditional
}
}
i++;
}
// If we read fully the last section of pixels and filled up our counters -- or filled
// the last counter but ran off the side of the image, OK. Otherwise, a problem.
- if (!(counterPosition == counters.length || (counterPosition == counters.length - 1 && i == end))) {
- throw new ReaderException("Couldn't fully read a pattern");
+ if (!(counterPosition == numCounters || (counterPosition == numCounters - 1 && i == end))) {
+ throw ReaderException.getInstance();
}
}
/**
* Determines how closely a set of observed counts of runs of black/white values matches a given
- * target pattern. For each counter, the ratio of the difference between it and the pattern value
- * is compared to the expected pattern value. This ratio is averaged across counters to produce
- * the return value. 0.0 means an exact match; higher values mean poorer matches.
+ * target pattern. This is reported as the ratio of the total variance from the expected pattern
+ * proportions across all pattern elements, to the length of the pattern.
*
* @param counters observed counters
* @param pattern expected pattern
- * @return average variance between counters and pattern
+ * @param maxIndividualVariance The most any counter can differ before we give up
+ * @return ratio of total variance between counters and pattern compared to total pattern size,
+ * where the ratio has been multiplied by 256. So, 0 means no variance (perfect match); 256 means
+ * the total variance between counters and patterns equals the pattern length, higher values mean
+ * even more variance
*/
- protected static float patternMatchVariance(int[] counters, int[] pattern) {
- int total = 0;
+ static int patternMatchVariance(int[] counters, int[] pattern, int maxIndividualVariance) {
int numCounters = counters.length;
+ int total = 0;
int patternLength = 0;
for (int i = 0; i < numCounters; i++) {
total += counters[i];
patternLength += pattern[i];
}
- float unitBarWidth = (float) total / (float) patternLength;
+ if (total < patternLength) {
+ // If we don't even have one pixel per unit of bar width, assume this is too small
+ // to reliably match, so fail:
+ return Integer.MAX_VALUE;
+ }
+ // We're going to fake floating-point math in integers. We just need to use more bits.
+ // Scale up patternLength so that intermediate values below like scaledCounter will have
+ // more "significant digits"
+ int unitBarWidth = (total << INTEGER_MATH_SHIFT) / patternLength;
+ maxIndividualVariance = (maxIndividualVariance * unitBarWidth) >> INTEGER_MATH_SHIFT;
- float totalVariance = 0.0f;
+ int totalVariance = 0;
for (int x = 0; x < numCounters; x++) {
- float scaledCounter = (float) counters[x] / unitBarWidth;
- float width = pattern[x];
- float abs = scaledCounter > width ? scaledCounter - width : width - scaledCounter;
- totalVariance += abs / width;
+ int counter = counters[x] << INTEGER_MATH_SHIFT;
+ int scaledPattern = pattern[x] * unitBarWidth;
+ int variance = counter > scaledPattern ? counter - scaledPattern : scaledPattern - counter;
+ if (variance > maxIndividualVariance) {
+ return Integer.MAX_VALUE;
+ }
+ totalVariance += variance;
}
- return totalVariance / (float) numCounters;
+ return totalVariance / total;
}
- /**
- * Fast round method.
- *
- * @return argument rounded to nearest int
- */
- protected static int round(float f) {
- return (int) (f + 0.5f);
- }
+ // This declaration should not be necessary, since this class is
+ // abstract and so does not have to provide an implementation for every
+ // method of an interface it implements, but it is causing NoSuchMethodError
+ // issues on some Nokia JVMs. So we add this superfluous declaration:
+
+ public abstract Result decodeRow(int rowNumber, BitArray row, Hashtable hints) throws ReaderException;
}
projects / zxing.git / blobdiff