Acorn User: The RISC OS Graphics CD/Acorn User: The RISC OS Graphics CD.iso/utilities/sascha/_sascha/_readme/readme

Text File | 1997-05-11 | 8.5 KB | 221 lines

SASCHA - HELP DOCUMENT


This application can be used to convert a sprite into a text file. Sprites
can be defined in any mode (up to 16M colours), but only black and non-black
pixels are taken into account. Your result is an ASCII image of the sprite
which renders the best possible result in terms of details and shapes. The
result can be used as images or signatures in electronic text based mail or
messages, etc.

You are recommended to apply monochrome (black/white), lowres sprites. This
is because of the proper impression the picture may give to you before the
conversion. Colours are ignored, in fact. Some Sprite-to-ASCII applications
are based upon colours, but yield enormous text files consisting of series
of characters, where each character just corresponds with one colour
(pixel).

Sascha will produce a 'text image' which will roughly be as big as the
original sprite is. Experimenting with different sprite characteristics will
often lead to astonishing results. My experiments have taught me that three
kinds of sprite sources will yield satisfying results in most cases:

1. Draw files
A draw file consisting of lines, curves and shapes with a fair amount of
black and non-black areas can be used. Thin lines should be avoided - no
characters in your set would approach these close enough. I always start
selecting all the objects and applying a line width of - let's say - 4.
Then take a snapshot - a lowres mode is not a bad idea! - and drag the
snapshot directly onto Sascha.

2. JPEG files
High quality photo's in JPEG (JFIF) format often lead to impressive 'sharp'
text files, especially images of buildings! The first thing you should do
is: make it a 2 colour sprite. The best method to do this is linking it into
!ChangeFSI. Choose the 2-col option with rectangular pixels (MODE 0) in
'Sprite output', and select in any case the option 'Disable dithering' in
the submenu 'Processing'. Additionaly you may want to play around with the
options 'Expand dynamic range', 'Histogram equalisation', 'Black correction'
and 'Gamma correction' in order to adjust the balance between black and
white areas in your image. After this you can either immediately drag the
result (sprite) onto Sascha, or through Paint, which enables you to 'cut
out' the wanted piece.

Note that 'Black correction' often needs values between 10 and 100 in order
to make your picture brighter and 'Gamma correction' needs (broken) numbers
between - let's say - 0.2 and 5.0 to apply more black. Using a 'physical
file' (i.e. a file on a real filing system, not an application drag) for
!ChangeFSI will enable you to reprocess the JPEG image easily after
adjusting your options. Any zoom operation can be managed by ChangeFSI by
choosing for example 'Scaling->Custom 7:4 7:4'.

GIF and normal sprite files can be applied as well, but JPEGs will normally
give better results, because of the control of dithering (dithering should
be avoided).

3. Scan images
Save the output sprite directly into Sascha. Best results are obtained by
generating 2 col sprites with massive, non-dithered areas.


COLOUR ASPECT


Many images representing text (fonts) will not depend on the aspect of the
colours (dark characters on bright background, or vice versa). Nevertheless
photos will depend on this. Shadows - for example - should always be black,
whereas fair-headed people should have a bright area for their hair (and
skin) to prevent becoming 'negatives'. When creating images for these
purposes you should consider this, so be aware of the receiver using an
application (or device) with a bright or dark background! (E-mail often has
bright background, whereas WimpLink (Fidonet, Aconet) uses a black
background.)

Sascha can be configured to switch the colours of the display and the
colours of the input, separately.


OTHER OPTIONS


Using topbits (characters with codes beyond 126), may improve the quality of
the text image dramatically, but most mailers won't support this. Internet
e-mail, for example, can't manage characters with accents, etc. You should
only apply this option when:
- you are sure that the mailing process (if any) does not mess up these
  characters;
- you are sure that the receiver applies the same (system) font
  as you do
  (Latin1 for example).
See also chapter 'Character sets'.


DITHERING


This option will choose characters at random, rather than choosing always
the same character for the same piece. Typically a white area may be
represented as a whole bunch of 'M's', or as a combination of alternating
'M's' and 'W's', which are equally suitable. The dithering method is to be
improved.
Note that applying dithering to the input sprite in previous processes
(apps) will usually make the text image result considerably less distinct.


STRIP SPACES AT END


Redundant spaces at the end of the text lines will be removed, when this
option is selected. The appearance will not be influenced, but your text file
may become much smaller. Only in cases of 'cutting and pasting' disabling
this option can be sensible.


KEEP ASPECT RATIO


The Risc OS Desktop uses a (system) font which contists of matrices of 8 by
8 pixels. To make the characters more legible, they are vertically doubled
in hires modes. Tall fonts are easier to read. Note that when you apply the
'real' system font of hires modes (for example by going into the ShellCLI),
the characters are half the size. It is important to be aware of the font
which is used to display the final image. In most cases this will be the
desktop (system) font. Select in these cases the option 'Keep aspect ratio'.
Note that any hires sprite to be processed will be treated as a lowres
sprite, so quality decreases. You can check out the effect of this option by
consulting the menu item 'Image' in the menu of the result window ('Ignored
hires').


DISPLAYING THE TEXT IMAGES IN FONTS OTHER THAN SYSTEM FONT


Displaying in other fonts will not always mess up your image, but
anti-aliasing effects, proportional fonts (like Homerton) and large line
spacing may harm the impression of your picture severely.


CHARACTER SETS


Character sets to be applied are: Latin1 (all ASCII codes between 32 and
255, excluding 127), WimpLink (ASCII codes between 32 and 255, excluding
127, 141, 142, 143?), E-mail (ASCII codes between 32 and 126) and PC8
(32-255, except 127). This version of Sascha only supplies the WimpLink set.
In order to apply a set suitable for e-mail, you should now deselect 'Use
topbit characters'. WimpLink is a MailLink application for Risc OS Desktop
for Fidonet and alikes (Aconet) by Remco de Vreugd.


DEVELOPMENT

V2.08: bug removed: didn't use correct colours after startup with inverted
display colours configured (due to unremoved debug declarations)

Several options are to be implemented:
- improved dithering
- flexible character sets
- shift improvement (shifting your image a few scan lines up or down may
  improve the result!)
- configureable score evaluation
- improved redrawing speed
- etc.


COPYRIGHT AND DISSEMINATION


Sascha is copyright © Maarten J. Seinen, 1997. The application is in the
Public Domain, which means that it may freely be copied and passed around as
long as no modifications are made, no parts of the program or files will be
left out and no expenses - other than media expenses, like floppies or
telephone rates - are charged.

The program has been designed and tested carefully. However, the author
cannot accept liability for any loss or damage arising from the use of the
program or its files.


DEDICATION


The program is dedicated to Mrs Sacha de Boer, the gorgeous female
newscaster of the Dutch Broadcasting Organisation (NOS), Journaal, and can
be admired almost daily via the Dutch Public Channels 1, 2 or 3.

To contact the author:
Maarten J. Seinen (Seinen's Fiction), The Hague, The Netherlands
Fidonet:    2:281/644.44
Aconet:     77:8500/203.44
Tel/Fax:    + 31 (0) 70 3814318

You may also try these Internet e-mail addresses:
[e-mail]
[e-mail] (at work)
[e-mail]
(these addresses are not guaranteed to work, especially not the last one).


SPECIAL THANKS TO


Ab Steeman (http://www.riscysite.demon.nl, mailto:[e-mail])
for his support, advice and his icons.
Kees Grinwis (design improvement)
Joris Röling for this Help-application.


LATEST VERSION


can be obtained from http://www.riscysite.demon.nl/Sas.html


Please do not remit money to my account as it will jeopardize my
unemployment benefit. Donate the money to Acorn Computers in Cambridge,
Great Britain, instead, so I would be able to work with Risc OS or its
successors for the rest of my life, not needing to muddle along with a
Microsoft Operating System.

Maarten J. Seinen, 08 May 1997