~04/1995
This months article comprises information on two software items widely used on the Acorn Archimedes and BBC A3000. BBC B Emulator -------------- 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 ------------------------------------------------------------------- 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