/**
* Identify where the end of the middle / payload section ends.
*
* @param row row of black/white values to search
* @return Array, containing index of start of 'end block' and end of 'end
* block'
* @throws ReaderException
*/
int[] decodeEnd(BitArray row)
{
// For convenience, reverse the row and then
// search from 'the start' for the end block
row.reverse();
int endStart = skipWhiteSpace(row);
int[] endPattern;
try {
endPattern = findGuardPattern(row, endStart, END_PATTERN_REVERSED);
} catch (ReaderException e) {
// Put our row of data back the right way before throwing
row.reverse();
throw e;
}
// 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.
// ref: http://www.barcode-1.net/i25code.html
validateQuietZone(row, endPattern[0]);
// Now recalc the indicies of where the 'endblock' starts & stops to
// accomodate
// the reversed nature of the search
int temp = endPattern[0];
endPattern[0] = row.getSize() - endPattern[1];
endPattern[1] = row.getSize() - temp;
// Put the row back the righ way.
row.reverse();
return endPattern;
}
/**
* We're going to examine rows from the middle outward, searching alternately above and below the
* middle, and farther out each time. rowStep is the number of rows between each successive
* attempt above and below the middle. So we'd scan row middle, then middle - rowStep, then
* middle + rowStep, then middle - (2 * rowStep), etc.
* rowStep is bigger as the image is taller, but is always at least 1. We've somewhat arbitrarily
* decided that moving up and down by about 1/16 of the image is pretty good; we try more of the
* image if "trying harder".
*
* @param image The image to decode
* @param hints Any hints that were requested
* @return The contents of the decoded barcode
* @throws ReaderException Any spontaneous errors which occur
*/
private Result doDecode(MonochromeBitmapSource image, System.Collections.Hashtable hints)
{
int width = image.getWidth();
int height = image.getHeight();
BitArray row = new BitArray(width);
int middle = height >> 1;
bool tryHarder = hints != null && hints.ContainsKey(DecodeHintType.TRY_HARDER);
int rowStep = Math.Max(1, height >> (tryHarder ? 7 : 4));
int MaxLines;
if (tryHarder) {
MaxLines = height; // Look at the whole image, not just the center
} else {
MaxLines = 9; // Nine rows spaced 1/16 apart is roughly the middle half of the image
}
for (int x = 0; x < MaxLines; x++) {
// Scanning from the middle out. Determine which row we're looking at next:
int rowStepsAboveOrBelow = (x + 1) >> 1;
bool isAbove = (x & 0x01) == 0; // i.e. is x even?
int rowNumber = middle + rowStep * (isAbove ? rowStepsAboveOrBelow : -rowStepsAboveOrBelow);
if (rowNumber < 0 || rowNumber >= height) {
// Oops, if we run off the top or bottom, stop
break;
}
// Estimate black point for this row and load it:
try {
image.estimateBlackPoint(BlackPointEstimationMethod.ROW_SAMPLING, rowNumber);
} catch (ReaderException re) {
continue;
}
image.getBlackRow(rowNumber, row,0, width);
// While we have the image data in a BitArray, it's fairly cheap to reverse it in place to
// handle decoding upside down barcodes.
for (int attempt = 0; attempt < 2; attempt++) {
if (attempt == 1) { // trying again?
row.reverse(); // reverse the row and continue
}
try {
// Look for a barcode
Result result = decodeRow(rowNumber, row, hints);
// We found our barcode
if (attempt == 1) {
// But it was upside down, so note that
result.putMetadata(ResultMetadataType.ORIENTATION, 180);
// And remember to flip the result points horizontally.
ResultPoint[] points = result.getResultPoints();
points[0] = (ResultPoint) new GenericResultPoint(width - points[0].getX() - 1, points[0].getY());
points[1] = (ResultPoint)new GenericResultPoint(width - points[1].getX() - 1, points[1].getY());
}
return result;
} catch (ReaderException re) {
// continue -- just couldn't decode this row
}
}
}
throw new ReaderException();
}
