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1997-04-13
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____________________________________________________________________________
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Compact Sprite and JPEG viewer for machines
equipped with the JPEG-capable SpriteExtend module
by David Thomas, ⌐ 1996-7
version 0.31 (13 Apr 1997)
____________________________________________________________________________
Introduction ______________________________________________________________
IBrowse is a fast and compact Sprite and JPEG image viewer for RISC OS
computers equipped with version 0.99 or later of the SpriteExtend module.
This version of SpriteExtend is built into RISC OS 3.6 and later versions,
and is available as a soft-loadable module for RISC OS 3.5 machines.
IBrowse was created to be quick, convenient and run in as little memory as
possible, for this reason it doesnæt provide some of the more advanced
features of image viewers, such as Éslideshowingæ. However it does support
app-to-app transfers, view scaling and does run in the tiny wimpslot of 8K -
you can load about forty copies of IBrowse for the same amount of memory
that Paint takes up. :-)
If you have RISC OS 3.5, there are details of how to obtain the
SpriteExtend module later on in this file. If IBrowse is run without this
version of SpriteExtend available then it will restrict itself to displaying
Sprites only.
PseudoMem _________________________________________________________________
This release of IBrowse features support for Gordon Rogersæ most seriously
excellent PseudoMem module, which implements a virtual memory system using
the dynamic area interface.
Once configured, all images are Éloadedæ into a PseudoMem dynamic area and
plotted straight from it, so the speed of display is often slow. However,
by using this you can view, in just a few Kb, images that previously would
have required many megabytes of memory.
PseudoMem also, very helpfully, fixes the bug in SpriteExtend which stops
small applications from using the JPEG plotting calls. (This is why IBrowse
always loads the PseudoMem module, even when not configured to utilise it).
Usage ____________________________________________________________________
Drag a Sprite or JPEG file to the IBrowse icon bar icon. A window will
open displaying the file. Also, double-clicking on a Sprite or JPEG file
when IBrowse is loaded will load it.
In addition to the standard Info and Quit entries on the icon bar menu,
there is also a ÉChoices...æ entry which, when selected will open the
choices window which allows you to set the types of dithering used on the
display. The options there, are :
Sprite Choices _________________________________________________________
Å ÉSimple ditheringæ - uses a simple patterning technique in most modes
which helps lessen the banding effect you get when you display deep
Sprites in paletted modes. My preference is to leave this option
off, as it seems to make Sprites look worse in certain cases.
( Note that the patterning technique will not always appear
immediately on the display. Sometimes a change of screen
mode is needed to Ékickæ it into action. )
Å ÉLoad on double-clickæ - will make IBrowse respond to double-clicks
on Sprite files, which it will automatically load. This option is
off by default as most Sprite files will have more than one Sprite in
them and IBrowse will only display the first.
JPEG Dithering _________________________________________________________
Å ÉNo ditheringæ - performs no dithering so the image may look Ébandedæ
in 256 and less colour modes. However, it is the quickest display
method.
Å ÉSimple ditheringæ - uses a simple patterning technique in most modes
which helps lessen the banding effect.
Å ÉError diffusionæ - is the slowest display method but provides a much
better quality of display. This method only works for 256 colour
modes, in other colour depths this is equivalent to ÉSimpleæ. It is
the default.
It is worth noting that even with Error diffusion, in paletted modes the
display quality will never be as good as that produced by ChangeFSI.
Use ChangeFSI if youære converting a JPEG image permanently to a Sprite.
Memory _________________________________________________________________
Å ÉUse PseudoMemæ - enables support for the PseudoMem module. Once
activated all images given to IBrowse for display will be rendered
straight from disc. This means that you can view images which are
bigger than your computeræs free memory, at the expense of speed.
At the bottom of the Choices window are two buttons. ÉSaveæ allows you to
save your choices (which will be stored in the !Boot.Choices directory).
ÉCancelæ restores your most recently saved choices from disc.
A menu is available from the display window with the following entries :
Å ÉImageæ - leads to an information box which provides various details
about the currently loaded image.
Å ÉChoices...æ - opens the choices window, as described above.
Å ÉScaleæ - leads to a small dialogue which allows you to change the
current view scale. The scale is specified as a percentage of the
original imageæs dimensions. However, note that the value you
specify works on both the x and y axis, so a É200%æ scaled image is
in fact four times larger than normal.
IBrowse will use a dynamic area for storage of the image. IBrowse is
compatible with Clareæs Virtualise package, although only when PseudoMem
support is disabled. (Attempting to Virtualise a PseudoMem area will lead
to serious crashes!).
Obtaining The SpriteExtend Module _________________________________________
If you are using RISC OS 3.5 and do not already have it, the SpriteExtend
0.99 module is available from ftp.acorn.co.uk in the pub/riscos/releases
directory under the name Éspriteextend.arcæ. It was also present on the
Acorn User CD-ROM 2, in the ÉRESOURCEæ directory under the name
ÉSPRITEXT/SPKæ.
There is a bug in version 0.99 of SpriteExtend which means tiny programs
like IBrowse will not work unless theyære given 24K of memory. This was a
serious issue with previous versions of IBrowse as they had to be given a
24K wimpslot. However if you have the PseudoMem module loaded - as IBrowse
does by default - it automatically handles the bug for us, allowing IBrowse
to run in 8K. :-)
Justin Fletcher has created ÉDummy Dynamic Areasæ (DDA) to enable RISC OS
3.1 users to use the JPEG-capable SpriteExtend. You can mail him at
ÉGerph@essex.ac.ukæ for details or preferably see his web pages at
Éhttp://users.essex.ac.uk/users/gerphæ.
Credits __________________________________________________________________
Thanks to Gordon Rogers for PseudoMem, which is rather good. :-) The
documentation for PseudoMem is contained within the IBrowse application
directory.
IBrowse was written in ObjAsm assembler, as Iæd paid a large wodge of cash
for Acorn C/C++ and I had to use it for /something/ didnæt I... ;-)
History __________________________________________________________________
0.31 (13 Apr 1997) - Wimp_ProcessKey wasn't being called for unused key
events, so F12 didn't work if the caret was in the
scale window.
- The PaletteChange message wasn't being acted on.
(JFletcher)
- The info window's style display was giving an
incorrect readout.
0.30 (19 Feb 1997) - Largely restructured and rewritten to alleviate many
problems and allow more features.
- Scaling.
- PseudoMem support is optional.
- Choices saving and loading.
- Images smaller than the mininum window size now
display with the windowæs the background filled
black.
- Only 12 bytes short of 8K now!
0.21p(01 Feb 1997) - PseudoMem release.
0.20 (16 Jan 1997) - First PD release.
- Slight modifications here and there.
- Will now work on Éplainæ OS 3.5.
0.15 (03 Jul 1996) - Added Sprite support, with optional dithering.
- SpriteExtend 0.99 is now available for RISC OS 3.5
machines, so RO 3.5 users can use IBrowse now.
- Needs an 8K slot now, rather than 4K as before.
- Error diffusion is now the default.
0.08 (18 Mar 1996) - More error checking.
(06 Apr 1996) - Docs updated.
(18 Apr 1996) - Slight change to the templates.
- Fixed version of HelpFile.
0.07 (07 Mar 1996) - Fix of mouse button click on choices window.
0.06 (02 Mar 1996) - Fixed scrapfile handling to return error.
- RISC OS 3.5+ -friendly error routine.
0.05 (29 Feb 1996) - Added Scrap file handling.
- Window close functions.
0.02 (26 Feb 1996) - Beta test release, only given to a couple of people.
Copyright and Contact Addresses ___________________________________________
This software is copyrighted work of David Thomas, it is supplied öas isò;
using it is entirely at your own risk. I make no warranty as to the fitness
of this software for any purpose. You are free to distribute this
application to anyone you please, as long as you are not supplying it for
personal gain and it is delivered with all the supplied files unaltered.
If you have any comments, bug reports, suggestions for future versions or
anything else donæt hesitate to contact me at -
Mail: Mr D.P. Thomas
20 Rosebery Avenue
Waterloo
Liverpool
L22 2BH
Email: CMSDTHOM@livjm.ac.uk
WWW: http://java.cms.livjm.ac.uk/cmsdthom/
The latest versions of my applications will be available from my World
Wide Web pages, where term dates allow.
____________________________________________________________________________