QPainter: antialiasing forces lighter horizontal/vertical straight line color

When painting simple straight vertical (or horizontal lines) 1px in width using the render hint QPainter::Antialiasing the pen color doesn't necessarily get used as it is at all. Only a much lighter variant of it. So for example if painter pen color is set to Qt::red which is documented as "Red (#ff0000)" the line may end up drawn 2px in width and completely in #ff7f7f which is clearly lighter color.

The expectation for the output would be that half of the drawn line would be in the selected color (#ff0000) in this case.

Steps to reproduce the problem:

1. run the attached project and check the colors of the lines (antialiasing enabled)

NOTE: To compare the result without antialiasing pass "-no-antialiasing" to the executable.