Contour correction

When I check "Spectrogram, Contour Plot" example, I found that some contour lines close to the center of circle are not continues. There must be some wrong.

After go through "qwt_raster_data.cpp", I found 2 bugs:

1. intersect function:
case 6:
// e(-1,1,0), e(1,0,-1)
line[0] = vertex[1].toPoint();
line[1] = intersection( vertex[0], vertex[1] );
break;
should be:
case 6:
// e(-1,1,0), e(1,0,-1)
line[0] = vertex[2].toPoint();
line[1] = intersection( vertex[0], vertex[1] );
break;

2. contourLines function:
if ( ignoreOutOfRange )
{
if ( !range.contains( zMin ) || !range.contains( zMax ) )
continue;
}
this is not correct. How about rang.max>zMax and rang.min<zMin?
should be:
if ( ignoreOutOfRange )
{
if ( range.maxValue()<Min ) || range.minValue()> zMax ) )
continue;
}