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ISSUE: http://code.google.com/p/zxing/issues/detail?id=110

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Changes to fix high nbr of false positives.
- Fixed up the quiet zone checks.
- Validate that the barcode fills the viewfinder
- Check that decoded barcode is min 6 digits


git-svn-id: https://zxing.googlecode.com/svn/trunk@755 59b500cc-1b3d-0410-9834-0bbf25fbcc57
This commit is contained in:
kev.sully 2008-11-21 11:25:45 +00:00
parent 1e9123b0af
commit 85506667a7
1 changed files with 55 additions and 15 deletions
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70
core/src/com/google/zxing/oned/ITFReader.java
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@ -93,7 +93,11 @@ public class ITFReader extends AbstractOneDReader {
decodeMiddle(row, startRange[1], endRange[0], result);
String resultString = result.toString();
if (resultString.length() == 0 || resultString.length() % 2 == 1)
/**
* To avoid false positives with 2D barcodes, make
* an assumption that the decoded string must be at least 6 digits.
*/
if (resultString.length() < 6 || resultString.length() % 2 == 1)
throw ReaderException.getInstance();
return new Result(resultString,
@ -164,20 +168,58 @@ public class ITFReader extends AbstractOneDReader {
*/
this.narrowLineWidth = (startPattern[1] - startPattern[0]) / 4;
/**
* The start & end patterns must be pre/post fixed by a quiet zone. This
* zone must be at least 10 times the width of a narrow line.
*
* ref: http://www.barcode-1.net/i25code.html
*/
if (this.narrowLineWidth * 10 > startPattern[0]) {
// Unable to find the quiet zone preceeding the start sequence.
throw ReaderException.getInstance();
}
validateQuietZone(row, startPattern[0]);
return startPattern;
}
/**
*
*
*/
/**
*
* The start & end patterns must be pre/post fixed by a quiet zone. This
* zone must be at least 10 times the width of a narrow line. Scan back until
* we either get to the start of the barcode or match the necessary number of
* quiet zone pixels.
*
* Note: Its assumed the row is reversed when using this method to find
* quiet zone after the end pattern.
*
* ref: http://www.barcode-1.net/i25code.html
*
* @param row - The bit array representing the scanned barcode.
* @param startPattern - The index into row of the start or end pattern.
* @throws ReaderException - If the quiet zone cannot be found, a ReaderException is thrown.
*/
private void validateQuietZone(BitArray row, int startPattern) throws ReaderException {
int quietCount=this.narrowLineWidth * 10; // expect to find this many pixels of quiet zone
int i=0;
for (i=startPattern-1; quietCount>0 && i>=0; i--)
{
if (row.get(i)==true)
break;
quietCount--;
}
if (quietCount!=0)
{
// Unable to find the necessary number of quiet zone pixels.
throw ReaderException.getInstance();
}
if (i>this.narrowLineWidth*20)
{
// The distance from the image edge to the start of the quiet zone
// is twice the size of the quiet zone.
// This is unrealistic as the barcode should mostly fill the camera viewfinder.
// This implies that this is a false positive.
throw ReaderException.getInstance();
}
}
/**
* Skip all whitespace until we get to the first black line.
*
@ -234,10 +276,8 @@ public class ITFReader extends AbstractOneDReader {
*
* ref: http://www.barcode-1.net/i25code.html
*/
if (this.narrowLineWidth * 10 > endPattern[0]) {
// Unable to find the quiet zone preceeding the start sequence.
throw ReaderException.getInstance();
}
validateQuietZone(row, endPattern[0]);
// Now recalc the indicies of where the 'endblock' starts & stops to
// accomodate