labelComponent alpha value

[pauls0323]

at imageProjection.cpp Line 416,
if ((*iter).first == 0) this means thisIndX and fromInx are equal，and thisIndY and fromIndY are different，and also means thisPoint and fromPoint are in the same vertiacal line, so the the alpha should be euqal to segmentAlphaY.But in Line 417 alpha = segmentAlphaX. Is there any question about my understanding? Any one who can help me? Thanks!