[Blindmath] Version 0.0.1 of ShapeExtractor02 is now available fordownload

Wed Feb 15 22:21:34 UTC 2012

Hello Dick and everyone,

What are you doing to make the slider usable by a blind person? Keep up the 
great work.

Peter Donahue

----- Original Message ----- 
From: "Richard Baldwin" <baldwin at dickbaldwin.com>
To: "BlindMath Mailing List" <blindmath at nfbnet.org>; 
<accessibleimage at freelists.org>
Sent: Wednesday, February 15, 2012 2:31 PM
Subject: [Blindmath] Version 0.0.1 of ShapeExtractor02 is now available 
fordownload

There are about 16-million good reasons why the embossed version of a
full-color bitmap image often fails to produce satisfactory tactile
results. Begin with the fact that the embossing process often discards the
information content of more than 16-million colors ending up with what is
effectively black and white, or possibly black and white with two or three
shades of gray in between, depending on the embossing method.

This is illustrated by the two round images in the attached image files.
One image shows a typical color wheel made up of a mixture of red, green,
and blue primary color values. The other image shows the result of
transforming that color image into a four-level grayscale image. The black,
gray, and white bands in the grayscale image identify the original colors
that would probably be indistinguishable in a four-level embossed image of
the color wheel.

Follow the loss of color information with the fact that, unless the
original image is very small, the spatial sampling is probably reduced by a
factor of 5 to 10 in the embossed image with little or no consideration
being given to frequency aliasing that occurs in a brute-force spatial
re-sampling process.

The bottom line is that it is difficult to emboss full-color bitmap images
and end up with high-quality tactile images.

In some cases, it is possible to pre-process an image in a way that will
cause it to produce a better embossed result than would be the case without
such pre-processing. The new free program named ShapeExtractor02 is
designed with that purpose in mind. I explain this more fully in the html
document that is attached to this message.

The four attached images of the horse show what I mean by pre-processing
the image to produce an improved embossed image.

One image shows a full-color image of a beautiful brown hourse.

A second image shows a four or five level grayscale version of the horse
image. This is pretty much what you would see if you were to copy the image
to a multi-level embosser. Essentially, you would see large areas of dots
whose heights are slightly different from dots in adjoining areas. It
remains to be seen if a blind student could pick a horse out of that. If
you were to copy this to a black and white (dot or no dot) embosser, you
probably would not get anything that would be recognizable as a horse.

Another image shows a pre-processed version of the horse image with black,
white, and three levels of gray in between. The major difference between
this image and the simple grayscale image is that this image tends to
outline the salient features of the original image with black and fill in
the outline with shades of gray. Thus, you don't see large areas of pixels
all having the same color of gray. Instead, you see outlines of shapes that
identify the salient features of the original image. That is why this
program is named ShapeExtractor. I believe that an embossed version of this
image would be more recognizable as a horse than an embossed version of the
grayscale image on a multi-level embosser.

Another attached image shows a black and white version of the pre-processed
image of the horse. I'm confident that this would be more recognizable that
the grayscale image on a black and white embosser and would probably also
be more recognizable on a multi-level embosser..

In all cases, a good description would be needed to help the student to
understand the embossed image.

I am pleased to announce that Version 0.0.1 of the new program
named ShapeExtractor02 is now posted at
http://www.austincc.edu/baldwin/SWT-SVG/SVGDraw01.zip and is available for
free and immediate downloading. (To save space on the server, the new
program is encapsulated in a zip file along with some earlier programs.)
This new program was used to produce two of the horse images that are
attached to this message.

This program accepts a bitmap image as input and writes the enhanced output
in a jpg bitmap file that can be embossed using any process that accepts a
jpg file as input. For example, if you and your students are fortunate to
have access to an IVEO system, you could import the enhanced image into
IVEO and add audio descriptions of the key features of the image. Then
emboss the updated image on a Tiger and allow the student to explore the
upgraded image on an IVEO touchpad.

The program makes it easy for sighted teachers and others who assist blind
students to enhance bitmap images for possible improved embosser
performance. An onscreen display shows the enhanced version of the image so
it isn't necessary to emboss it to evaluate the success or lack thereof of
the enhancement process. An onscreen slider makes it possible to easily
adjust the enhancement parameters for best performance.

This program can also be used by blind students for the same purpose using
default settings. Even though blind students can't operate the slider to
optimize the output, the default settings will often produce an improved
embossed image.

To use this free program, simply download the zip file using the link that
is provided above, extract the contents of the zip file into an empty
Windows folder, read the file named __ReadMeFirst.txt, and start processing
bitmap files.

A copy of the user instruction file is attached to this message for direct
reading. Another copy of the instructions, with images intact, is contained
in the attached zip file.

Please let me know if this program works for you and provide suggestions
for improvement.

Dick Baldwin

> --
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/

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