public override Result decodeRow(int rowNumber, BitArray row, Dictionary<DecodeHintType, Object> hints)
{
int[] start = findAsteriskPattern(row);
int nextStart = start[1];
int end = row.Size;
// Read off white space
while (nextStart < end && !row.get_Renamed(nextStart))
{
nextStart++;
}
var result = new StringBuilder(20);
var counters = new int[9];
char decodedChar;
int lastStart;
do
{
recordPattern(row, nextStart, counters);
int pattern = toNarrowWidePattern(counters);
if (pattern < 0)
{
throw ReaderException.Instance;
}
decodedChar = patternToChar(pattern);
result.Append(decodedChar);
lastStart = nextStart;
for (int i = 0; i < counters.Length; i++)
{
nextStart += counters[i];
}
// Read off white space
while (nextStart < end && !row.get_Renamed(nextStart))
{
nextStart++;
}
} while (decodedChar != '*');
result.Remove(result.Length - 1, 1); // remove asterisk
// Look for whitespace after pattern:
int lastPatternSize = 0;
for (int i = 0; i < counters.Length; i++)
{
lastPatternSize += counters[i];
}
int whiteSpaceAfterEnd = nextStart - lastStart - lastPatternSize;
// If 50% of last pattern size, following last pattern, is not whitespace, fail
// (but if it's whitespace to the very end of the image, that's OK)
if (nextStart != end && whiteSpaceAfterEnd/2 < lastPatternSize)
{
throw ReaderException.Instance;
}
if (usingCheckDigit)
{
int max = result.Length - 1;
int total = 0;
for (int i = 0; i < max; i++)
{
total += ALPHABET_STRING.IndexOf((Char) result[i]);
}
if (total%43 != ALPHABET_STRING.IndexOf((Char) result[max]))
{
throw ReaderException.Instance;
}
result.Remove(max, 1);
}
String resultString = result.ToString();
if (extendedMode)
{
resultString = decodeExtended(resultString);
}
if (resultString.Length == 0)
{
// Almost surely a false positive
throw ReaderException.Instance;
}
float left = (start[1] + start[0])/2.0f;
float right = (nextStart + lastStart)/2.0f;
return new Result(resultString, null,
new[] {new ResultPoint(left, rowNumber), new ResultPoint(right, rowNumber)},
BarcodeFormat.CODE_39);
}
private static int[] findAsteriskPattern(BitArray row)
{
int width = row.Size;
int rowOffset = 0;
while (rowOffset < width)
{
if (row.get_Renamed(rowOffset))
{
break;
}
rowOffset++;
}
int counterPosition = 0;
var counters = new int[9];
int patternStart = rowOffset;
bool isWhite = false;
int patternLength = counters.Length;
for (int i = rowOffset; i < width; i++)
{
bool pixel = row.get_Renamed(i);
if (pixel ^ isWhite)
{
counters[counterPosition]++;
}
else
{
if (counterPosition == patternLength - 1)
{
if (toNarrowWidePattern(counters) == ASTERISK_ENCODING)
{
// Look for whitespace before start pattern, >= 50% of width of start pattern
if (row.isRange(Math.Max(0, patternStart - (i - patternStart)/2), patternStart, false))
{
return new[] {patternStart, i};
}
}
patternStart += counters[0] + counters[1];
for (int y = 2; y < patternLength; y++)
{
counters[y - 2] = counters[y];
}
counters[patternLength - 2] = 0;
counters[patternLength - 1] = 0;
counterPosition--;
}
else
{
counterPosition++;
}
counters[counterPosition] = 1;
isWhite = !isWhite;
}
}
throw ReaderException.Instance;
}
/// <summary> Skip all whitespace until we get to the first black line.
///
/// </summary>
/// <param name="row">row of black/white values to search
/// </param>
/// <returns> index of the first black line.
/// </returns>
/// <throws> ReaderException Throws exception if no black lines are found in the row </throws>
private static int skipWhiteSpace(BitArray row)
{
int width = row.Size;
int endStart = 0;
while (endStart < width)
{
if (row.get_Renamed(endStart))
{
break;
}
endStart++;
}
if (endStart == width)
{
throw ReaderException.Instance;
}
return endStart;
}
/// <param name="row"> row of black/white values to search
/// </param>
/// <param name="rowOffset">position to start search
/// </param>
/// <param name="pattern"> pattern of counts of number of black and white pixels that are
/// being searched for as a pattern
/// </param>
/// <returns> start/end horizontal offset of guard pattern, as an array of two
/// ints
/// </returns>
/// <throws> ReaderException if pattern is not found </throws>
private static int[] findGuardPattern(BitArray row, int rowOffset, int[] pattern)
{
// TODO: This is very similar to implementation in UPCEANReader. Consider if they can be
// merged to a single method.
int patternLength = pattern.Length;
var counters = new int[patternLength];
int width = row.Size;
bool isWhite = false;
int counterPosition = 0;
int patternStart = rowOffset;
for (int x = rowOffset; x < width; x++)
{
bool pixel = row.get_Renamed(x);
if (pixel ^ isWhite)
{
counters[counterPosition]++;
}
else
{
if (counterPosition == patternLength - 1)
{
if (patternMatchVariance(counters, pattern, MAX_INDIVIDUAL_VARIANCE) < MAX_AVG_VARIANCE)
{
return new[] {patternStart, x};
}
patternStart += counters[0] + counters[1];
for (int y = 2; y < patternLength; y++)
{
counters[y - 2] = counters[y];
}
counters[patternLength - 2] = 0;
counters[patternLength - 1] = 0;
counterPosition--;
}
else
{
counterPosition++;
}
counters[counterPosition] = 1;
isWhite = !isWhite;
}
}
throw ReaderException.Instance;
}
/// <summary> 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
///
/// </summary>
/// <param name="row">bit array representing the scanned barcode.
/// </param>
/// <param name="startPattern">index into row of the start or end pattern.
/// </param>
/// <throws> ReaderException if the quiet zone cannot be found, a ReaderException is thrown. </throws>
private void validateQuietZone(BitArray row, int startPattern)
{
int quietCount = narrowLineWidth*10; // expect to find this many pixels of quiet zone
for (int i = startPattern - 1; quietCount > 0 && i >= 0; i--)
{
if (row.get_Renamed(i))
{
break;
}
quietCount--;
}
if (quietCount != 0)
{
// Unable to find the necessary number of quiet zone pixels.
throw ReaderException.Instance;
}
}
