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Completely rewrote the algorithm for detecting finder-like patterns, making it more accurate and compliant with the QR Code specification, in all languages.

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Project Nayuki
2018-10-26 06:53:12 +00:00
parent 5ac0e2a938
commit af872343c0
8 changed files with 292 additions and 138 deletions
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cpp/QrCode.cpp
+33 -19
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@@ -428,8 +428,9 @@ int QrCode::handleConstructorMasking(int mask) {
long QrCode::getPenaltyScore() const {
long result = 0;
// Adjacent modules in row having same color
// Adjacent modules in row having same color, and finder-like patterns
for (int y = 0; y < size; y++) {
std::deque<int> runHistory(7, 0);
bool color = false;
int runX = 0;
for (int x = 0; x < size; x++) {
@@ -440,13 +441,22 @@ long QrCode::getPenaltyScore() const {
else if (runX > 5)
result++;
} else {
addRunToHistory(runX, runHistory);
if (!color && hasFinderLikePattern(runHistory))
result += PENALTY_N3;
color = module(x, y);
runX = 1;
}
}
addRunToHistory(runX, runHistory);
if (color)
addRunToHistory(0, runHistory); // Dummy run of white
if (hasFinderLikePattern(runHistory))
result += PENALTY_N3;
}
// Adjacent modules in column having same color
// Adjacent modules in column having same color, and finder-like patterns
for (int x = 0; x < size; x++) {
std::deque<int> runHistory(7, 0);
bool color = false;
int runY = 0;
for (int y = 0; y < size; y++) {
@@ -457,10 +467,18 @@ long QrCode::getPenaltyScore() const {
else if (runY > 5)
result++;
} else {
addRunToHistory(runY, runHistory);
if (!color && hasFinderLikePattern(runHistory))
result += PENALTY_N3;
color = module(x, y);
runY = 1;
}
}
addRunToHistory(runY, runHistory);
if (color)
addRunToHistory(0, runHistory); // Dummy run of white
if (hasFinderLikePattern(runHistory))
result += PENALTY_N3;
}
// 2*2 blocks of modules having same color
@@ -474,23 +492,6 @@ long QrCode::getPenaltyScore() const {
}
}
// Finder-like pattern in rows
for (int y = 0; y < size; y++) {
for (int x = 0, bits = 0; x < size; x++) {
bits = ((bits << 1) & 0x7FF) | (module(x, y) ? 1 : 0);
if (x >= 10 && (bits == 0x05D || bits == 0x5D0)) // Needs 11 bits accumulated
result += PENALTY_N3;
}
}
// Finder-like pattern in columns
for (int x = 0; x < size; x++) {
for (int y = 0, bits = 0; y < size; y++) {
bits = ((bits << 1) & 0x7FF) | (module(x, y) ? 1 : 0);
if (y >= 10 && (bits == 0x05D || bits == 0x5D0)) // Needs 11 bits accumulated
result += PENALTY_N3;
}
}
// Balance of black and white modules
int black = 0;
for (const vector<bool> &row : modules) {
@@ -544,6 +545,19 @@ int QrCode::getNumDataCodewords(int ver, Ecc ecl) {
}
void QrCode::addRunToHistory(int run, std::deque<int> &history) {
history.pop_back();
history.push_front(run);
}
bool QrCode::hasFinderLikePattern(const std::deque<int> &runHistory) {
int n = runHistory.at(1);
return n > 0 && runHistory.at(2) == n && runHistory.at(4) == n && runHistory.at(5) == n
&& runHistory.at(3) == n * 3 && std::max(runHistory.at(0), runHistory.at(6)) >= n * 4;
}
bool QrCode::getBit(long x, int i) {
return ((x >> i) & 1) != 0;
}