DmtxFollow FollowSeek(DmtxRegion reg, int seek)
{
int i;
int sign;
DmtxFollow follow = new DmtxFollow();
follow.Loc = reg.FlowBegin.Loc;
follow.Step = 0;
follow.Ptr = this._cache;
follow.PtrIndex = DecodeGetCache(follow.Loc.X, follow.Loc.Y);
sign = (seek > 0) ? +1 : -1;
for (i = 0; i != seek; i += sign)
{
follow = FollowStep(reg, follow, sign);
if (Math.Abs(follow.Step) > reg.StepsTotal)
{
throw new Exception("Follow step count larger total step count!");
}
}
return follow;
}
DmtxFollow FollowStep(DmtxRegion reg, DmtxFollow followBeg, int sign)
{
int patternIdx;
int stepMod;
int factor;
DmtxFollow follow = new DmtxFollow();
if (Math.Abs(sign) != 1)
{
throw new Exception("Invalid parameter 'sign', can only be -1 or +1");
}
factor = reg.StepsTotal + 1;
if (sign > 0)
stepMod = (factor + (followBeg.Step % factor)) % factor;
else
stepMod = (factor - (followBeg.Step % factor)) % factor;
/* End of positive trail -- magic jump */
if (sign > 0 && stepMod == reg.JumpToNeg)
{
follow.Loc = reg.FinalNeg;
}
/* End of negative trail -- magic jump */
else if (sign < 0 && stepMod == reg.JumpToPos)
{
follow.Loc = reg.FinalPos;
}
/* Trail in progress -- normal jump */
else
{
patternIdx = (sign < 0) ? followBeg.Neighbor & 0x07 : ((followBeg.Neighbor & 0x38) >> 3);
follow.Loc = new DmtxPixelLoc() { X = followBeg.Loc.X + DmtxConstants.DmtxPatternX[patternIdx], Y = followBeg.Loc.Y + DmtxConstants.DmtxPatternY[patternIdx] };
}
follow.Step = followBeg.Step + sign;
follow.Ptr = this._cache;
follow.PtrIndex = DecodeGetCache(follow.Loc.X, follow.Loc.Y);
return follow;
}
DmtxFollow FollowStep2(DmtxFollow followBeg, int sign)
{
int patternIdx;
DmtxFollow follow = new DmtxFollow();
if (Math.Abs(sign) != 1)
{
throw new Exception("Invalid parameter 'sign', can only be -1 or +1");
}
if ((followBeg.Neighbor & 0x40) == 0x00)
{
throw new Exception("Invalid value for neighbor!");
}
patternIdx = (sign < 0) ? followBeg.Neighbor & 0x07 : ((followBeg.Neighbor & 0x38) >> 3);
follow.Loc = new DmtxPixelLoc() { X = followBeg.Loc.X + DmtxConstants.DmtxPatternX[patternIdx], Y = followBeg.Loc.Y + DmtxConstants.DmtxPatternY[patternIdx] };
follow.Step = followBeg.Step + sign;
follow.Ptr = this._cache;
follow.PtrIndex = DecodeGetCache(follow.Loc.X, follow.Loc.Y);
return follow;
}
DmtxFollow FollowSeekLoc(DmtxPixelLoc loc)
{
DmtxFollow follow = new DmtxFollow();
follow.Loc = loc;
follow.Step = 0;
follow.Ptr = this._cache;
follow.PtrIndex = DecodeGetCache(follow.Loc.X, follow.Loc.Y);
return follow;
}
