/// <summary> 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".
///
/// </summary>
/// <param name="image">The image to decode
/// </param>
/// <param name="hints">Any hints that were requested
/// </param>
/// <returns> The contents of the decoded barcode
/// </returns>
/// <throws> ReaderException Any spontaneous errors which occur </throws>
private Result doDecode(BinaryBitmap image, System.Collections.Generic.Dictionary <Object,Object> hints)
{
int width = image.Width;
int height = image.Height;
BitArray row = new BitArray(width);
int middle = height >> 1;
bool tryHarder = hints != null && hints.ContainsKey(DecodeHintType.TRY_HARDER);
int rowStep = System.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
{
row = image.getBlackRow(rowNumber, row);
}
catch (ReaderException re)
{
continue;
}
// 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
// This means we will only ever draw result points *once* in the life of this method
// since we want to avoid drawing the wrong points after flipping the row, and,
// don't want to clutter with noise from every single row scan -- just the scans
// that start on the center line.
if (hints != null && hints.ContainsKey(DecodeHintType.NEED_RESULT_POINT_CALLBACK))
{
System.Collections.Generic.Dictionary <Object,Object> newHints = new System.Collections.Generic.Dictionary <Object,Object>(); // Can't use clone() in J2ME
System.Collections.IEnumerator hintEnum = hints.Keys.GetEnumerator();
//UPGRADE_TODO: Method 'java.util.Enumeration.hasMoreElements' was converted to 'System.Collections.IEnumerator.MoveNext' which has a different behavior. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1073_javautilEnumerationhasMoreElements'"
while (hintEnum.MoveNext())
{
//UPGRADE_TODO: Method 'java.util.Enumeration.nextElement' was converted to 'System.Collections.IEnumerator.Current' which has a different behavior. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1073_javautilEnumerationnextElement'"
System.Object key = hintEnum.Current;
if (!key.Equals(DecodeHintType.NEED_RESULT_POINT_CALLBACK))
{
newHints[key] = hints[key];
}
}
hints = newHints;
}
}
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, (System.Object) 180);
// And remember to flip the result points horizontally.
ResultPoint[] points = result.ResultPoints;
points[0] = new ResultPoint(width - points[0].X - 1, points[0].Y);
points[1] = new ResultPoint(width - points[1].X - 1, points[1].Y);
}
return result;
}
catch (ReaderException re)
{
// continue -- just couldn't decode this row
}
}
}
throw ReaderException.Instance;
}
