[Shotwell] Red-Eyes

[Lucas Beeler]

Hi Charles,

First, thank you very much for your interest in Shotwell! I appreciate
your comments and suggestions about the functionality of the red-eye
tool. To address your points:

> the best solution would be possibilty of choice of the new nuance (from
> white to black) of the pupil

We could consider this for an upcoming release of Shotwell. Indeed,
I've ticketed it here: http://trac.yorba.org/ticket/2148 .

> the red pupil is replaced by light-grey pupil, which looks like dead eye ...
> in fact pupils are black, isn't it?

Yes, pupils are black, but the viewer rarely perceives them as black.
This is because the surface of the human eye is moist and highly
reflective. As a result, pupils are shiny and reflect light very well.
So most of the time, they appear to be a gunmetal or lead gray color.
What's more, because they are so shiny, pupils have a reflectance
distribution across their surface. So some areas of the pupil will be
silvery-white because of the light they reflect while others will
appear jet-black.

When we designed the red-eye feature in Shotwell, it was very
important to us to try to maintain this natural distribution of
reflected light. So we don't just fill the pixels with black or gray
like some other programs. Instead, we attempt to extract luminance
information from the green and blue channels and transfer it evenly
into the red channel, thus preserving the natural highlights of the
pupil. This is why your pupil appears light gray. It's not an artifact
of Shotwell. It's the way the pupil was naturally lit. Does that make
sense?

Take care,
Lucas

--------------------------------
Lucas Beeler
Software Designer
Yorba Foundation