/*
- * 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.
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 com.google.zxing.common.GenericResultPoint;
import java.util.Hashtable;
*/
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 {
- boolean tryHarder = hints != null && hints.containsKey(DecodeHintType.TRY_HARDER);
try {
- return doDecode(image, hints, tryHarder);
+ 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, tryHarder);
+ Result result = doDecode(rotatedImage, hints);
// Record that we found it rotated 90 degrees CCW / 270 degrees CW
Hashtable metadata = result.getResultMetadata();
int orientation = 270;
}
}
- private Result doDecode(MonochromeBitmapSource image, Hashtable hints, boolean tryHarder) throws ReaderException {
-
+ /**
+ * 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; we try more of the image if
- // "trying harder"
int middle = height >> 1;
+ boolean tryHarder = hints != null && hints.containsKey(DecodeHintType.TRY_HARDER);
int rowStep = Math.max(1, height >> (tryHarder ? 7 : 4));
int maxLines;
- //if (tryHarder || barcodesToSkip > 0) {
if (tryHarder) {
- maxLines = height; // Look at the whole image; looking for more than one barcode
+ maxLines = height; // Look at the whole image, not just the center
} else {
- maxLines = 7;
+ maxLines = 9; // Nine rows spaced 1/16 apart is roughly the middle half of the image
}
- Hashtable lastResults = null;
- boolean skippingSomeBarcodes = hints != null && hints.containsKey(DecodeHintType.SKIP_N_BARCODES);
-
for (int x = 0; x < maxLines; x++) {
// Scanning from the middle out. Determine which row we're looking at next:
}
image.getBlackRow(rowNumber, row, 0, width);
- // We may try twice for each row, if "trying harder":
+ // 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?
- if (tryHarder) { // only if "trying harder"
- row.reverse(); // reverse the row and continue
- } else {
- break;
- }
+ row.reverse(); // reverse the row and continue
}
-
try {
-
// Look for a barcode
Result result = decodeRow(rowNumber, row, hints);
-
- if (lastResults != null && lastResults.containsKey(result.getText())) {
- // Just saw the last barcode again, proceed
- continue;
+ // 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 GenericResultPoint(width - points[0].getX() - 1, points[0].getY());
+ points[1] = new GenericResultPoint(width - points[1].getX() - 1, points[1].getY());
}
-
- if (skippingSomeBarcodes) { // See if we should skip and keep looking
- int oldValue = ((Integer) hints.get(DecodeHintType.SKIP_N_BARCODES)).intValue();
- if (oldValue > 1) {
- hints.put(DecodeHintType.SKIP_N_BARCODES, new Integer(oldValue - 1));
- } else {
- hints.remove(DecodeHintType.SKIP_N_BARCODES);
- skippingSomeBarcodes = false;
- }
- if (lastResults == null) {
- lastResults = new Hashtable(3);
- }
- lastResults.put(result.getText(), Boolean.TRUE); // Remember what we just saw
- } else {
- // We found our barcode
- if (attempt == 1) {
- // But it was upside down, so note that
- result.putMetadata(ResultMetadataType.ORIENTATION, new Integer(180));
- }
- return result;
- }
-
+ return result;
} catch (ReaderException re) {
// continue -- just couldn't decode this row
}
-
}
}
throw new ReaderException("No barcode found");
}
+ /**
+ * 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++) {
/**
* Determines how closely a set of observed counts of runs of black/white values matches a given
- * 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.
+ * 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
*/
- 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;
+ 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) patternLength;
+ return totalVariance / total;
}
+ // 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