Linux-Tag: Image Viewer for people who are blind

Dave Mielke dave at mielke.cc
Sun Jun 26 16:30:30 UTC 2005


[quoted lines by Sébastien Hinderer on 2005/06/26 at 08:55 +0200]

>Nevertheless, I tried to explore a circle, and could hardly follow it.
>Perhaps it's a lack of training, but for me it wa very difficult to use
>the system.

We blind people will tend to have a very difficult time understanding pictures,
which are accurate representations of what sighted people see. There are at
least two reasons for this:

First: A sighted person doesn't really look straight at something. Were he to
do so, he'd see everything double since both his eyes aren't in the exact same
place. What he actually does is turn each eye slightly toward the centre so
that they can both focus on the same point of interest. In addition, the rays
of light which enter his eyes to show him what he's looking at are angled such
that they all cross through a single point (one for each eye), giving him the
ability to see wider areas at greater distances. One effect of these is that
objects which are truly parallel appear to him to converge in the distance. A
picture of a hallway, for example, would show its two sides getting closer and
closer together, whereas we blind people think of them, even in the distance,
as being the same distance apart.

Second: A sighted person learns by expedrience to infer a lot of useful details
from all of the lines which he sees, much in the same way that we blind people
learn to estimate distance by the time it takes for an echo to return,
direction by the difference in time that the same sound arrives at each ear,
etc. We think of a cube as a simple, six-sided object no matter how it's
positioned. Were it tipped slightly up on one of its corners, however, a
sighted person would see what to him is clear, but to us would be a hopeless
maze of lines (which reveal where the light can get through and where it
can't).

Let's say you were using this device to look at the graphic of a pushbutton in
a form on your screen. You of course want to know if the button is pressed or
not. A sighted person would know at a glance, but how he does so isn't really
that obvious. He essentially does so by making a deduction based on which side
of the button the light is reflecting from. If it's pressed then the light
reflects from the farther side of the inside of the frame,, whereas if it isn't
pressed then it reflects from the nearer side of the button itself. His
deduction is made even more complex by his assumption regarding which direction
the virtual light in the picture is coming from.

-- 
Dave Mielke           | 2213 Fox Crescent | I believe that the Bible is the
Phone: 1-613-726-0014 | Ottawa, Ontario   | Word of God. Please contact me
EMail: dave at mielke.cc | Canada  K2A 1H7   | if you're concerned about Hell.
http://FamilyRadio.com/                   | http://Mielke.cc/bible/




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