int TrailBlazeGapped(DmtxRegion reg, DmtxBresLine line, int streamDir)
{
bool onEdge;
int distSq, distSqMax;
int travel = 0;
int outward = 0;
int xDiff, yDiff;
int steps;
int stepDir = 0;
int[] dirMap = { 0, 1, 2, 7, 8, 3, 6, 5, 4 };
bool err;
DmtxPixelLoc beforeStep, afterStep;
DmtxPointFlow flow, flowNext;
DmtxPixelLoc loc0;
int xStep, yStep;
loc0 = line.Loc;
flow = GetPointFlow(reg.FlowBegin.Plane, loc0, DmtxConstants.DmtxNeighborNone);
distSqMax = (line.XDelta * line.XDelta) + (line.YDelta * line.YDelta);
steps = 0;
onEdge = true;
beforeStep = loc0;
int beforeCacheIndex = DecodeGetCache(loc0.X, loc0.Y);
if (beforeCacheIndex == -1)
return 0;
else
_cache[beforeCacheIndex] = 0;
do
{
if (onEdge == true)
{
flowNext = FindStrongestNeighbor(flow, streamDir);
if (flowNext.Mag == DmtxConstants.DmtxUndefined)
break;
err = (new DmtxBresLine(line)).GetStep(flowNext.Loc, ref travel, ref outward);
if (flowNext.Mag < 50 || outward < 0 || (outward == 0 && travel < 0))
{
onEdge = false;
}
else
{
line.Step(travel, outward);
flow = flowNext;
}
}
if (!onEdge)
{
line.Step(1, 0);
flow = GetPointFlow(reg.FlowBegin.Plane, line.Loc, DmtxConstants.DmtxNeighborNone);
if (flow.Mag > 50)
onEdge = true;
}
afterStep = line.Loc;
int afterCacheIndex = DecodeGetCache(afterStep.X, afterStep.Y);
if (afterCacheIndex == -1)
break;
/* Determine step direction using pure magic */
xStep = afterStep.X - beforeStep.X;
yStep = afterStep.Y - beforeStep.Y;
if (Math.Abs(xStep) > 1 || Math.Abs(yStep) > 1)
{
throw new Exception("Invalid step directions!");
}
stepDir = dirMap[3 * yStep + xStep + 4];
if (stepDir == 8)
{
throw new Exception("Invalid step direction!");
}
if (streamDir < 0)
{
this._cache[beforeCacheIndex] |= (byte)(0x40 | stepDir);
this._cache[afterCacheIndex] = (byte)(((stepDir + 4) % 8) << 3);
}
else
{
this._cache[beforeCacheIndex] |= (byte)(0x40 | (stepDir << 3));
this._cache[afterCacheIndex] = (byte)((stepDir + 4) % 8);
}
/* Guaranteed to have taken one step since top of loop */
xDiff = line.Loc.X - loc0.X;
yDiff = line.Loc.Y - loc0.Y;
distSq = (xDiff * xDiff) + (yDiff * yDiff);
beforeStep = line.Loc;
beforeCacheIndex = afterCacheIndex;
steps++;
} while (distSq < distSqMax);
return steps;
}
