23/02/95
This months article comprises information on two software items widely
used on the Acorn Archimedes and BBC A3000.

BBC B Emulator 
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Acorn has developed an enhanced Model B emulator for RISC OS. This has been
made available at a special discount for use in Educational institutions in
the UK and for Software Developers registered with Acorn. Teachers should
approach their local LEA or IT centre for further information.

The disc comprises:

* improved version of !65Host, which emulates the BBC Model B environment;

* utilities such as DFS converters, picture converters to transfer BBC
screens to the Acorn Archimedes or BBC A3000 and a program which will scan
your BBC BASIC programs and check for any possible problems areas in them
which will cause problems when porting the programs across, all these
utilities are designed to help transfer and modify 6502-based programs for
use with RISC OS computers;

* examples to illustrate how to port existing 6502-based programs onto RISC
OS;

* comprehensive User Guide in electronic format( Text and Acorn DTP).  

ChangeFSI: Colour Image Processing Using a fixed set of 256 colours
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Archimedes computers have full colour display capabilities built into them
as standard. However, compared with the hardware found in larger
workstations, the facilities provided have been carefully reduced (in order
to make them cheap enough to fit all the time). So the precision of the
digital to analog converters is only 4 bits (instead of 8) and the colour
palette only has 16 entries (instead of 256).

This leads to a conversion problem for colour images built on other
machines. The solution involves colour Floyd Steinberg error diffusion to a
fixed colour palette and has implications for other machines, especially
when sequences of images or many images shown on the same display are
concerned.

In addition to solving this particular problem, a number of conventional
image enhancement algorithms (sharpening, dynamic range expansion, histogram
equalisation) and an "equal area" anti-aliased size scaling routine are all
incorporated in the same step, giving a maximal quality output.

The following image formats are supported by ChangeFSI:

RISC OS 1, 2, 4 and 8 bit per pixel sprites
Watford digitiser pictures 512x256y64g
   and triple red, green, blue separations
ProArtisan compressed pictures 640x256y256c
TimeStep satellite image 800x800y256g
TimeStep satellite image 128x256y256g
   and triple red, green, blue separations
!Translator "Clear" format
AIM/Wild Vision Hawk V10 files 256x256y256g
TIFF pictures 1-24 bits per pixel
Electronic Art's IFF ILBM pictures
Sun 'pixrect' raster files 1-24 bits per pixel
.PIC 8 bit per pixel files
MILLIPEDE PRISMA 768x574y 8 bit colour images
Compuserve's GIF files up to 8 bit per pixel
ZSoft PCX format 4/8 bit per pixel
MacPaint files 576x720y 1 bit per pixel
Windows 3 .BMP format 1/4/8 bits per pixel
Degas 1/2/4 bits per pixel colour images
Truevision "Targa" (both TGA and VDA)
Wild Vision V9 Colour images 512x256y12 bits
ArVis 15 bit HIP.+LOP. sprites 640x256y
Pineapple 16 bit colour images 512x256y
GEM IMG. images
UNIX "rle" files
PC EGA .DSP images 640x350y16c
MTV 24 bit pic. images
QRT 24 bit .raw images
RT 24 bit run length coded image. files