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Detector is now a little more skeptical once it has found 3 confirmed finder patterns -- one may be a false positive, so it also checks to see if the estimated module sizes are "pretty similar". If not, keeps looking.

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git-svn-id: https://zxing.googlecode.com/svn/trunk@394 59b500cc-1b3d-0410-9834-0bbf25fbcc57
This commit is contained in:
srowen 2008-05-08 15:12:44 +00:00
parent dbf5629def
commit 8d31073968
1 changed files with 22 additions and 7 deletions
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29
core/src/com/google/zxing/qrcode/detector/FinderPatternFinder.java
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@ -419,19 +419,34 @@ final class FinderPatternFinder {
/** /**
* @return true iff we have found at least 3 finder patterns that have been detected * @return true iff we have found at least 3 finder patterns that have been detected
* at least {@link #CENTER_QUORUM} times each * at least {@link #CENTER_QUORUM} times each, and, the estimated module size of the
* candidates is "pretty similar"
*/ */
private boolean haveMulitplyConfirmedCenters() { private boolean haveMulitplyConfirmedCenters() {
int count = 0; int confirmedCount = 0;
float totalModuleSize = 0.0f;
int max = possibleCenters.size(); int max = possibleCenters.size();
for (int i = 0; i < max; i++) { for (int i = 0; i < max; i++) {
if (((FinderPattern) possibleCenters.elementAt(i)).getCount() >= CENTER_QUORUM) { FinderPattern pattern = (FinderPattern) possibleCenters.elementAt(i);
if (++count == 3) { if (pattern.getCount() >= CENTER_QUORUM) {
return true; confirmedCount++;
} totalModuleSize += pattern.getEstimatedModuleSize();
} }
} }
return false; if (confirmedCount < 3) {
return false;
}
// OK, we have at least 3 confirmed centers, but, it's possible that one is a "false positive"
// and that we need to keep looking. We detect this by asking if the estimated module sizes
// vary too much. We arbitrarily say that when the total deviation from average exceeds
// 15% of the total module size estimates, it's too much.
float average = totalModuleSize / max;
float totalDeviation = 0.0f;
for (int i = 0; i < max; i++) {
FinderPattern pattern = (FinderPattern) possibleCenters.elementAt(i);
totalDeviation += Math.abs(pattern.getEstimatedModuleSize() - average);
}
return totalDeviation <= 0.15f * totalModuleSize;
} }
/** /**