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Fixed a bug in patternMatchVariance() which caused the max individual variance to never eliminate any patterns. As a result, the false positives unit test dropped from 15 to 4. Also did some other minor cleanup.

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git-svn-id: https://zxing.googlecode.com/svn/trunk@456 59b500cc-1b3d-0410-9834-0bbf25fbcc57
This commit is contained in:
dswitkin 2008-06-19 21:38:48 +00:00
parent e0db8f9271
commit 12e5d9462c
5 changed files with 33 additions and 25 deletions
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46
core/src/com/google/zxing/oned/AbstractOneDReader.java
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@ -36,20 +36,20 @@ import java.util.Hashtable;
public abstract class AbstractOneDReader implements OneDReader {
private static final int INTEGER_MATH_SHIFT = 8;
public static final int PATTERN_MATCH_RESULT_SCALE_FACTOR = 256;
public 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;
@ -65,27 +65,33 @@ public abstract class AbstractOneDReader implements OneDReader {
}
}
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) {
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
}
for (int x = 0; x < maxLines; x++) {
@ -179,12 +185,12 @@ public abstract class AbstractOneDReader implements OneDReader {
/**
* 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
* @param maxIndividualVariance
* @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
@ -207,7 +213,7 @@ public abstract class AbstractOneDReader implements OneDReader {
// Scale up patternLength so that intermediate values below like scaledCounter will have
// more "significant digits"
int unitBarWidth = (total << INTEGER_MATH_SHIFT) / patternLength;
maxIndividualVariance *= unitBarWidth;
maxIndividualVariance = (maxIndividualVariance * unitBarWidth) >> INTEGER_MATH_SHIFT;
int totalVariance = 0;
for (int x = 0; x < numCounters; x++) {

6
core/src/com/google/zxing/oned/AbstractUPCEANReader.java
View file

@ -36,7 +36,7 @@ import java.util.Hashtable;
public abstract class AbstractUPCEANReader extends AbstractOneDReader implements UPCEANReader {
private static final int MAX_AVG_VARIANCE = (int) (PATTERN_MATCH_RESULT_SCALE_FACTOR * 0.40625f);
private static final int MAX_INDIVIDUAL_VARIANCE = (int) (PATTERN_MATCH_RESULT_SCALE_FACTOR * 0.5f);
private static final int MAX_INDIVIDUAL_VARIANCE = (int) (PATTERN_MATCH_RESULT_SCALE_FACTOR * 0.7f);
/**
* Start/end guard pattern.
@ -140,8 +140,10 @@ public abstract class AbstractUPCEANReader extends AbstractOneDReader implements
* @throws ReaderException if the string does not contain only digits
*/
boolean checkChecksum(String s) throws ReaderException {
int sum = 0;
int length = s.length();
if (length == 0) return false;
int sum = 0;
for (int i = length - 2; i >= 0; i -= 2) {
int digit = (int) s.charAt(i) - (int) '0';
if (digit < 0 || digit > 9) {

2
core/src/com/google/zxing/oned/Code128Reader.java
View file

@ -143,7 +143,7 @@ public final class Code128Reader extends AbstractOneDReader {
};
private static final int MAX_AVG_VARIANCE = (int) (PATTERN_MATCH_RESULT_SCALE_FACTOR * 0.1875f);
private static final int MAX_INDIVIDUAL_VARIANCE = (int) (PATTERN_MATCH_RESULT_SCALE_FACTOR * 0.25f);
private static final int MAX_INDIVIDUAL_VARIANCE = (int) (PATTERN_MATCH_RESULT_SCALE_FACTOR * 0.35f);
private static final int CODE_SHIFT = 98;

2
core/test/src/com/google/zxing/common/FalsePositivesBlackBoxTestCase.java
View file

@ -35,7 +35,7 @@ import java.io.IOException;
public final class FalsePositivesBlackBoxTestCase extends AbstractBlackBoxTestCase {
// This number should be reduced as we get better at rejecting false positives.
private static final int FALSE_POSITIVES_ALLOWED = 15;
private static final int FALSE_POSITIVES_ALLOWED = 4;
// Use the multiformat reader to evaluate all decoders in the system.
public FalsePositivesBlackBoxTestCase() {

2
core/test/src/com/google/zxing/oned/EAN8BlackBox1TestCase.java
View file

@ -30,7 +30,7 @@ public final class EAN8BlackBox1TestCase extends AbstractBlackBoxTestCase {
public EAN8BlackBox1TestCase() {
super(new File("test/data/blackbox/ean8-1"), new MultiFormatReader(), BarcodeFormat.EAN_8);
addTest(8, 0.0f);
addTest(7, 180.0f);
addTest(8, 180.0f);
}
}