ITF: support shorter ITF symbols (2, 3 or 4 depending on heuristic)

axxel · axxel · commit 8fb2f81841de · 2024-10-22T11:04:30.000+02:00
If we are looking only for ITF symbols, the minimum length is now 4 instead of 6. If the symbol covers the whole image, this gets halved, so 2 or 3 respectively. This fixes #853 without introducing any false positive for our sample data-set.
diff --git a/core/src/oned/ODITFReader.cpp b/core/src/oned/ODITFReader.cpp
@@ -15,7 +15,7 @@ namespace ZXing::OneD {
 
 Barcode ITFReader::decodePattern(int rowNumber, PatternView& next, std::unique_ptr<DecodingState>&) const
 {
-	const int minCharCount = 6;
+	const int minCharCount = _opts.formats().count() == 1 ? 4 : 6; // if we are only looking for ITF, we accept shorter symbols
 	const int minQuietZone = 6; // spec requires 10
 
 	next = FindLeftGuard(next, 4 + minCharCount/2 + 3, FixedPattern<4, 4>{1, 1, 1, 1}, minQuietZone);
@@ -33,6 +33,8 @@ Barcode ITFReader::decodePattern(int rowNumber, PatternView& next, std::unique_p
 
 	constexpr int weights[] = {1, 2, 4, 7, 0};
 	int xStart = next.pixelsInFront();
+	bool startsAtFirstBar = next.isAtFirstBar();
+
 	next = next.subView(4, 10);
 
 	std::string txt;
@@ -62,17 +64,18 @@ Barcode ITFReader::decodePattern(int rowNumber, PatternView& next, std::unique_p
 
 	next = next.subView(0, 3);
 
-	if (Size(txt) < minCharCount || !next.isValid())
-		return {};
-
 	// Check quiet zone size
-	if (!(next.isAtLastBar() || next[3] > minQuietZone * (threshold.bar + threshold.space) / 3))
+	if (!next.isValid() || !(next.isAtLastBar() || next[3] > minQuietZone * (threshold.bar + threshold.space) / 3))
 		return {};
 
 	// Check stop pattern
 	if (next[0] < threshold[0] || next[1] > threshold[1] || next[2] > threshold[2])
 		return {};
 
+	// Check min length depending on whether the code covers the complete image or not
+	if (Size(txt) < (startsAtFirstBar && next.isAtLastBar() ? (minCharCount / 2) : minCharCount))
+		return {};
+
 	Error error = _opts.validateITFCheckSum() && !GTIN::IsCheckDigitValid(txt) ? ChecksumError() : Error();
 
 	// Symbology identifier ISO/IEC 16390:2007 Annex C Table C.1
diff --git a/test/blackbox/BlackboxTestRunner.cpp b/test/blackbox/BlackboxTestRunner.cpp
@@ -464,9 +464,9 @@ int runBlackBoxTests(const fs::path& testPathPrefix, const std::set<std::string>
 			{ 3, 5, 180 },
 		}, ReaderOptions().setEanAddOnSymbol(EanAddOnSymbol::Require));
 
-		runTests("itf-1", "ITF", 11, {
-			{ 10, 11, 0   },
-			{ 10, 11, 180 },
+		runTests("itf-1", "ITF", 12, {
+			{ 11, 12, 0   },
+			{ 11, 12, 180 },
 		});
 
 		runTests("itf-2", "ITF", 6, {
diff --git a/test/samples/itf-1/#853.png b/test/samples/itf-1/#853.png
diff --git a/test/samples/itf-1/#853.txt b/test/samples/itf-1/#853.txt
@@ -0,0 +1 @@
+1515
