Bad HUE blend method

Can someone confirm that how the attached file looks like once rendered?
-G
hue2.sifz (827 Bytes)

Like this
Quality 3, AA 1
hue2.png

Like this
Quality 3, AA 1

This is my result on Synfig Studio 0.63.05 64 bits Mac OSX 10.7.5
AA=1
Q=3

:frowning:
-G
hue2.png

This is my result on Synfig Studio 0.63.05 64 bits Ubuntu 12.04 LTS
AA=1
Q=3

:frowning:
-G
hue2.png

This is my result on Synfig Studio 0.63.05 32 bits Ubuntu 12.04 LTS
AA=1
Q=3
:open_mouth: :open_mouth:
-G
hue2.png

And this is my result using the CAIRO_OPERATOR_HSL_HUE on my development branch in the above Mac machine:
If we look to the Hue definition it says that the resulting color has the hue of the source and the luminosity and the saturation of the backdrop.
But what’s the hue of a color?
According to wikipedia formula for the hue of a color when the color has all its channels with the same value it is needed to calculate the atan2 of x=0 and y=0. That’s a problem! If both coordinates are zero what’s the arc it holds!!??
Researching here it says:
Sometimes, neutral colors (i.e. with C = 0) are assigned a hue of 0° for convenience of representation.
So I think that the Cairo result is the correct one (commonly accepted for a undefined value).
Any comment?
-G
hue2-cairo.png

Here’s what I got on KDE, Fedora 17 (uses a different compositor to GNOME):

hue2.png