// --------------------------------------------------------------
private Boolean isRegionIgnored(FLTDataRegionalizer.Region region)
{
Boolean ignored = false;
if (region.spanList.Count == 1)
{
// single span (and thus row) region
ignored = true;
}
else if (region.minCol == region.maxCol)
{
// single column region
ignored = true;
}
return(ignored);
}
// --------------------------------------------------------------
public void generate(FLTDataRegionalizer.Region region)
{
// Notes:
// - As regions are taken from data points arranged like pixels on a screen, direction labels are relative to a coordinate
// system with origin at top left corner, with x increasing to the 'right' and y increasing 'down'.
// - Algorithm starts at the top left (i.e. northwestern) most point in the region, and crawls around the region in a
// counter-clockwise manner.
if (null == _addPointHandler)
{
throw new System.InvalidOperationException("RegionHullGenerator: addPointHandler has not been set");
}
// test rejection cases
if (isRegionIgnored(region))
{
return;
}
// start at left edge of left most span on minimum row (which region helpfully already knows)
var startSpan = region.minRowMinColSpan;
var currentSpan = startSpan;
Tuple <int, int> currentPoint = null;
// travel direction correlates to movement on the rows (1 ==> downward), though no math is done
// using this, it is strictly a logical indicator
const int UP = -1;
const int DOWN = 1;
var currentRowTravelDirection = DOWN;
Boolean done = false;
while (false == done)
{
//Console.WriteLine("loop current span id : " + currentSpan.Id + " traveling " + (currentRowTravelDirection > 0 ? "down" : "up"));
if (DOWN == currentRowTravelDirection)
{
// traveling down
// get point from LEFT end of current span because travel is CCW around the region, so if traveling down
// must be going down left side
currentPoint = new Tuple <int, int>(currentSpan.start, currentSpan.row);
addPoint(currentPoint);
// If there are no more spans to follow downward, start going up.
if (false == currentSpan.hasSpansBelow)
{
// leave current span same, next loop iteration will begin
// going up at right edge of current span
currentRowTravelDirection = UP;
}
else
{
// Have a span below this one...
if (false == currentSpan.hasLeftSibling)
{
// If current span has no left sibling, step down to the left most
// span below current and continue downward.
currentSpan = currentSpan.spansBelow.First();
}
else
{
// Have a left sibling...
// Check to see if current span and its left sibling share the span below (and not above).
// Picture this as a little 'bowl' with the bottom formed by the span below, and the sides
// formed by this span and its left sibling.
if ((currentSpan.spanLeft.hasSpansBelow) &&
(currentSpan.spansBelow.First().Id == currentSpan.spanLeft.spansBelow.Last().Id))
{
// traverse the bottom of the 'bowl'
// step to point below left end of current span...
currentPoint = new Tuple <int, int>(currentSpan.start, currentSpan.row + 1);
addPoint(currentPoint);
// step over to point on span below that is beneath left sibling's end...
currentPoint = new Tuple <int, int>(currentSpan.spanLeft.end, currentSpan.row + 1);
addPoint(currentPoint);
// set currentSpan to left sibling, and begin upward traveling from there
currentSpan = currentSpan.spanLeft;
currentRowTravelDirection = UP;
}
else
{
// current span and left don't share a sibling (means shared span is above)
// continue downward normally
currentSpan = currentSpan.spansBelow.First();
}
} // end else has left sibling
} // end has spans below
} // end if traveling down
else
{
// traveling up
// get point from RIGHT end of current span because travel is CCW around the region, so if traveling up
// must be going up right side
currentPoint = new Tuple <int, int>(currentSpan.end, currentSpan.row);
addPoint(currentPoint);
// If there are no more spans to follow upward, start going down again (from same span).
if (false == currentSpan.hasSpansAbove)
{
currentRowTravelDirection = DOWN;
}
else
{
// Have a span above this one, but we need to see if it overlaps a sibling
// to current span's right.
if (false == currentSpan.hasRightSibling)
{
// If current span has no right sibling, move up to the right most
// span above current and continue upward.
currentSpan = currentSpan.spansAbove.Last();
}
else
{
// Have a right sibling.
// See if right sibling and current span share a span above (and not below).
// Picture this situation as an upside down bowl, or lowercase 'n', with the sides
// formed by currentSpan and its right sibling, and the 'top' formed by
// the span above.
if ((currentSpan.spanRight.hasSpansAbove) &&
(currentSpan.spansAbove.Last().Id == currentSpan.spanRight.spansAbove.First().Id))
{
// step to point above right end of current...
currentPoint = new Tuple <int, int>(currentSpan.end, currentSpan.row - 1);
addPoint(currentPoint);
// step over to point on span above that is over right sibling's start...
currentPoint = new Tuple <int, int>(currentSpan.spanRight.start, currentSpan.row - 1);
addPoint(currentPoint);
// set currentSpan to right sibling and begin downward travel from there
currentSpan = currentSpan.spanRight;
currentRowTravelDirection = DOWN;
}
else
{
// no shared span with sibling (can ignore sibling)
// set current to span above and continue normally
currentSpan = currentSpan.spansAbove.Last();
}
}
} // end else has above span
} // end else traveling up
// detect if returned to the start span and halt
// If my deductive abilities are correct, that last step will always be upward, because we SHOULD
// always have started at the minimum (i.e. highest on screen) row span.
// NOTE: after the halt case make sure we don't skip adding the final point from the startSpan. This should
// always be the right end of the startSpan, because we should always be starting at the left end of the span
if (currentSpan == startSpan)
{
currentPoint = new Tuple <int, int>(currentSpan.end, currentSpan.row);
addPoint(currentPoint);
done = true;
}
} // end while !done
}
