/// <summary>
/// Gets the decoded codeword value.
/// </summary>
/// <returns>The decoded codeword value.</returns>
/// <param name="moduleBitCount">Module bit count.</param>
private static int GetDecodedCodewordValue(int[] moduleBitCount)
{
int decodedValue = GetBitValue(moduleBitCount);
return(PDF417Common.GetCodeword(decodedValue) == PDF417Common.INVALID_CODEWORD ? PDF417Common.INVALID_CODEWORD : decodedValue);
}
/// <summary>
/// Detects the codeword.
/// </summary>
/// <returns>The codeword.</returns>
/// <param name="image">Image.</param>
/// <param name="minColumn">Minimum column.</param>
/// <param name="maxColumn">Max column.</param>
/// <param name="leftToRight">If set to <c>true</c> left to right.</param>
/// <param name="startColumn">Start column.</param>
/// <param name="imageRow">Image row.</param>
/// <param name="minCodewordWidth">Minimum codeword width.</param>
/// <param name="maxCodewordWidth">Max codeword width.</param>
private static Codeword DetectCodeword(BitMatrix image,
int minColumn,
int maxColumn,
bool leftToRight,
int startColumn,
int imageRow,
int minCodewordWidth,
int maxCodewordWidth)
{
startColumn = AdjustCodewordStartColumn(image, minColumn, maxColumn, leftToRight, startColumn, imageRow);
// we usually know fairly exact now how long a codeword is. We should provide minimum and maximum expected Length
// and try to adjust the read pixels, e.g. remove single pixel errors or try to cut off exceeding pixels.
// min and maxCodewordWidth should not be used as they are calculated for the whole barcode an can be inaccurate
// for the current position
int[] moduleBitCount = GetModuleBitCount(image, minColumn, maxColumn, leftToRight, startColumn, imageRow);
if (moduleBitCount == null)
{
return(null);
}
int endColumn;
int codewordBitCount = PDF417Common.GetBitCountSum(moduleBitCount);
if (leftToRight)
{
endColumn = startColumn + codewordBitCount;
}
else
{
for (int i = 0; i < moduleBitCount.Length >> 1; i++)
{
int tmpCount = moduleBitCount[i];
moduleBitCount[i] = moduleBitCount[moduleBitCount.Length - 1 - i];
moduleBitCount[moduleBitCount.Length - 1 - i] = tmpCount;
}
endColumn = startColumn;
startColumn = endColumn - codewordBitCount;
}
// TODO implement check for width and correction of black and white bars
// use start (and maybe stop pattern) to determine if blackbars are wider than white bars. If so, adjust.
// should probably done only for codewords with a lot more than 17 bits.
// The following fixes 10-1.png, which has wide black bars and small white bars
// for (int i = 0; i < moduleBitCount.Length; i++) {
// if (i % 2 == 0) {
// moduleBitCount[i]--;
// } else {
// moduleBitCount[i]++;
// }
// }
// We could also use the width of surrounding codewords for more accurate results, but this seems
// sufficient for now
if (!CheckCodewordSkew(codewordBitCount, minCodewordWidth, maxCodewordWidth))
{
// We could try to use the startX and endX position of the codeword in the same column in the previous row,
// create the bit count from it and normalize it to 8. This would help with single pixel errors.
return(null);
}
int decodedValue = PDF417CodewordDecoder.GetDecodedValue(moduleBitCount);
int codeword = PDF417Common.GetCodeword(decodedValue);
if (codeword == -1)
{
return(null);
}
return(new Codeword(startColumn, endColumn, GetCodewordBucketNumber(decodedValue), codeword));
}