[Blindmath] grayscale braille

Tue Mar 20 18:42:46 UTC 2012

Hi Michael,

You wrote:

"may not really give the same impression as the visual things you describe
as one never reads/views Braille at a distance so won't get that point of
not really resolving individual dots but rather a general effect."

In this respect, I was thinking in terms of embossed images as opposed to
single line Braille displays. It seems to me that brushing your hand across
an embossed image and being aware of the dot density at different locations
on the image might be somewhat analogous to viewing a printer-art image
from a distance.

Dick B.

On Tue, Mar 20, 2012 at 1:26 PM, Michael Whapples <mwhapples at aim.com> wrote:

> Wow, what a lot of information.
>
> I hadn't heard of the making a grayscale image with people before, I knew
> people have used lots of people to create images by having people wearing
> different colours though.
>
> Back to the actual subject, I thought you might have been interested as I
> know with some of your image processing you have commented on how low the
> grayscale resolution (shades of gray resolution) is with existing
> technology. However the increase in gray levels comes at a very high cost
> of spatial resolution, is 40 pixels wide, may be 80 for very rich/lucky
> people with such a Braille display, really good enough? I have my doubts
> even for those with 80 cell displays, the display is so long will one
> really get a proper awareness of what relates to what because of the spread?
>
> Another question is, why only use letters? Surely one could potentially
> use up to 64 for a 6-dot cell and on a Braille display one could get full
> 256 level representation!
>
> I like your thought of number of dots for level as it would make it
> intuitive, but does then bring down the number of levels and may not really
> give the same impression as the visual things you describe as one never
> reads/views Braille at a distance so won't get that point of not really
> resolving individual dots but rather a general effect.
>
> To try to keep to some sort of logical assignment, if trying for the 256
> levels, then I would just use binary around the Braille cell (eg. lightest
> being no dots, next coming dot-1, next being dot-2, next being dots-12,...
> very nearly black dots-2345678, darkest dots-12345678).
>
> Michael Whapples
>
> -----Original Message----- From: Richard Baldwin
> Sent: Tuesday, March 20, 2012 4:37 PM
>
> To: Blind Math list for those interested in mathematics
> Subject: Re: [Blindmath] grayscale braille
>
> I have been following this conversation with interest. For the record, I am
> not blind and know very little about Braille. However, I do know quite a
> lot about image processing.
>
> In the sighted world, a character printer can definitely be used to produce
> gray scale images, but not in the way that is described here.
>
> In the 1960s, a typical data processing printer weighed several hundred
> pounds, stood chest high from the floor, printed upper-case letters,
> numbers, and a set of special characters at 10 characters per inch with a
> line length of 132 characters on 14-inch wide fan-fold paper. A typical
> data processing printer could print 600 lines per minute or more. With some
> printers, the paper came out so fast that special mechanisms were required
> to prevent it from flying across the room and to refold itself in the
> output bin.
>
> Many data centers had various examples of printer art posted on the walls
> with the most common being a reasonably good gray scale replica of the Mona
> Lisa.
>
> However, unlike the scheme that is described here, there was no intent for
> the viewer to assign special meaning to any individual character. In fact,
> the intent was for the characters to visually run together is such a way
> that they would not be perceived as characters at all. Instead, the big
> picture view of the printout would give the impression of a gray scale
> image with individual characters fading into the background.
>
> Someone came up with a sequence of characters based on the amount of ink
> deposited within the 0.1-inch wide cell by each character. That was a long
> time ago and I don't recall the specific sequence of characters that was
> used. I am guessing that the period character was used to convey light
> gray. Moving from there through the sequence, each character deposited more
> ink and therefore produced a darker cell. I'm also guessing that the
> sequence probably consisted of eight to ten different characters making it
> possible to produce the illusion of eight to ten levels of gray.
>
> Characters were chosen such that when a person stepped away from the
> printout and viewed it as a whole, that person didn't see individual
> characters. Instead, the result was an illusion of a large gray scale
> image.
>
> I used this scheme myself in the days before the invention of the CalComp
> incremental plotter to produce images of contour maps.
>
> Perhaps a similar scheme could be used with braille with each cell
> containing from zero to six dots (or perhaps eight dots). This might make
> it possible for a blind person to perceive white plus six (or eight) levels
> of gray without the requirement to mentally associate specific characters
> with specific shades of gray.
>
> For the six-dot case, the following sequence of characters might provide
> the illusion of increasing darkness (but a different selection might
> produce better tactile results):
>
> hex 41, A, 1 dot
> hex 42, B, 2 dots
> hex 44, D, 3 dots
> hex 47, G, 4 dots
> hex 51, Q, 5 dots
> hex 3D, =, 6 dots
>
> Dots have long been used to produce the illusion of gray scale images. When
> I was a youngster, pictures in most small-town newspapers were presented in
> gray scale because printing presses that could print in color were very
> expensive. If you looked closely at a newspaper photo, you could see that
> the picture was simply an array of dots. I seem to recall that the gray
> scale effect was achieved by producing an array of black dots on a uniform
> grid using different sized dots.
>
> At one point in time, I had some very interesting photographs from "Life"
> magazine involving very unique gray scale images. In those photos, a
> photographer produced images of various things, including a portrait of
> Woodrow Wilson and a picture of the U.S. Marine insignia by taking
> photographs of thousands of troops in formation wearing white shirts and
> black shirts. In effect, each person was one dot in the image.
>
> Apparently the photographer would place the camera on top of a building or
> tower and take of picture of the troops in formation down below. He even
> took perspective into account. For example, moving away from the camera,
> each row of troops was wider than the one before it. In some cases, the row
> of troops closest to the camera contained 20 or 30 troops while the most
> distant row would contain 200 to 300 troops. Thus, the "dot density"
> increased as you viewed the image going from bottom to top.
>
> I was able to find an image of a printer generated Mona Lisa on the web,
> but was unable to find any images of the human-dot photographs.
>
> Dick Baldwin
>
>
> On Mon, Mar 19, 2012 at 6:13 PM, Michael Whapples <mwhapples at aim.com>
> wrote:
>
>  I don't know if John is on the blindmath list, I'll forward the message on
>> in case he isn't, however it would be better if you could somehow
>> communicate direct with him (eg. by posting to the NFB-science list if he
>> isn't on blindmath).
>>
>> Michael Whapples
>>
>> -----Original Message----- From: Pranav Lal
>> Sent: Monday, March 19, 2012 10:58 PM
>> To: 'Blind Math list for those interested in mathematics'
>> Subject: Re: [Blindmath] grayscale braille
>>
>>
>> Hi John,
>>
>> Can I use this plotting technique for any image? Your example seems to
>> work
>> only for functions.
>>
>> Pranav
>>
>>
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>
>
> --
> Richard G. Baldwin (Dick Baldwin)
> Home of Baldwin's on-line Java Tutorials
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>
> Professor of Computer Information Technology
> Austin Community College
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-- 
Richard G. Baldwin (Dick Baldwin)
Home of Baldwin's on-line Java Tutorials
http://www.DickBaldwin.com

Professor of Computer Information Technology
Austin Community College
(512) 223-4758
mailto:Baldwin at DickBaldwin.com
http://www.austincc.edu/baldwin/