YES NOPE9 wrote:
> I believe I have seen a computer app that allows one to create
> posterization or half-tone posters from many small images.   The many
> small images create a pattern that looks like an image from a
> distance.
>
> I have searched intergurgle and found nothing.   I don't know the
> correct name for this technique.

It sounds like you are referring to halftoning, which is one of many method=
s
of dithering to achieve more intensity resolution at the expense of spacial
resolution.

The dithering strategy varies depending on the characteristics of the final
display medium.  If you want to make gray scale images with black ink, then
you use a fixed dot pitch but vary the diameters of the dots.  Newpaper
pictures use this technique, for example.  If the result is for display on =
a
monitor or where there is already a fixed grid of pixels, then you want a
dither pattern that is as high a frequency as possible.

The human visual system also should be considered.  For example, we are mor=
e
sensitive to horizontal and vertical lines as apposed to diagonal lines.
Therefore you want a dither pattern to be diagonal grid, not vertically and
horizontally aligned.

The first of the following three pictures is a full tone gray scale image,
and the other two dithered versions at 1 bit per pixel but using different
schemes:

http://www.embedinc.com/temp/a.gif
http://www.embedinc.com/temp/b.gif
http://www.embedinc.com/temp/c.gif

My program IMAGE_DITHER can be used to produce dithered images.  It is
included in the full release at http://www.embedinc.com/pic/dload.htm.  See
the doc file for details.


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.
--=20
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.