internal FinderPatternInfo Find(Hashtable hints)
{
bool tryHarder = hints?.ContainsKey(DecodeHintType.TRY_HARDER) == true;
int maxI = Image.Height;
int maxJ = Image.Width;
// We are looking for black/white/black/white/black modules in
// 1:1:3:1:1 ratio; this tracks the number of such modules seen so far
// Let's assume that the maximum version QR Code we support takes up 1/4 the height of the
// image, and then account for the center being 3 modules in size. This gives the smallest
// number of pixels the center could be, so skip this often. When trying harder, look for all
// QR versions regardless of how dense they are.
int iSkip = (3 * maxI) / (4 * MAX_MODULES);
if (iSkip < MIN_SKIP || tryHarder)
{
iSkip = MIN_SKIP;
}
bool done = false;
int[] stateCount = new int[5];
for (int i = iSkip - 1; i < maxI && !done; i += iSkip)
{
// Get a row of black/white values
stateCount[0] = 0;
stateCount[1] = 0;
stateCount[2] = 0;
stateCount[3] = 0;
stateCount[4] = 0;
int currentState = 0;
for (int j = 0; j < maxJ; j++)
{
if (Image.Get_Renamed(j, i))
{
// Black pixel
if ((currentState & 1) == 1)
{
// Counting white pixels
currentState++;
}
stateCount[currentState]++;
}
else
{
// White pixel
if ((currentState & 1) == 0)
{
// Counting black pixels
if (currentState == 4)
{
// A winner?
if (FoundPatternCross(stateCount))
{
// Yes
bool confirmed = HandlePossibleCenter(stateCount, i, j);
if (confirmed)
{
// Start examining every other line. Checking each line turned out to be too
// expensive and didn't improve performance.
iSkip = 2;
if (hasSkipped)
{
done = HaveMultiplyConfirmedCenters();
}
else
{
int rowSkip = FindRowSkip();
if (rowSkip > stateCount[2])
{
// Skip rows between row of lower confirmed center
// and top of presumed third confirmed center
// but back up a bit to get a full chance of detecting
// it, entire width of center of finder pattern
// Skip by rowSkip, but back off by stateCount[2] (size of last center
// of pattern we saw) to be conservative, and also back off by iSkip which
// is about to be re-added
i += rowSkip - stateCount[2] - iSkip;
j = maxJ - 1;
}
}
}
else
{
// Advance to next black pixel
do
{
j++;
}while (j < maxJ && !Image.Get_Renamed(j, i));
j--; // back up to that last white pixel
}
// Clear state to start looking again
currentState = 0;
stateCount[0] = 0;
stateCount[1] = 0;
stateCount[2] = 0;
stateCount[3] = 0;
stateCount[4] = 0;
}
else
{
// No, shift counts back by two
stateCount[0] = stateCount[2];
stateCount[1] = stateCount[3];
stateCount[2] = stateCount[4];
stateCount[3] = 1;
stateCount[4] = 0;
currentState = 3;
}
}
else
{
stateCount[++currentState]++;
}
}
else
{
// Counting white pixels
stateCount[currentState]++;
}
}
}
if (FoundPatternCross(stateCount))
{
bool confirmed = HandlePossibleCenter(stateCount, i, maxJ);
if (confirmed)
{
iSkip = stateCount[0];
if (hasSkipped)
{
// Found a third one
done = HaveMultiplyConfirmedCenters();
}
}
}
}
FinderPattern[] patternInfo = SelectBestPatterns();
ResultPoint.OrderBestPatterns(patternInfo);
return(new FinderPatternInfo(patternInfo));
}