Notable Use

I was looking at the excellent Chris’s Acorns site the other day, when I found another archetypal use of Christine Lord’s Oxford typeface on a BBC Micro peripheral:

Judging by the LEDs, it also doubles as a light show

This is precisely the sort of application for the Oxford face I remember seeing all over the place as a child. Whatever would the UK electronics industry have done without it?

When Yak met Goat

If you don’t know who the gentleman playing Repton: The Lost Realms is, then it’ll probably be impossible for me to explain how happy discovering this picture earlier this week made me feel.

You Know When You’ve Been Tango-ed

My friend Samwise and I are both enthusiastic users of the GNU/Linux operating system and also enormous fans of the incredible range of retro computing emulators produced by the brilliant Tom Walker.

Tom (left) and Samwise (right)

Photo courtesy regregex

There’s seemingly nothing that Tom isn’t able write an emulator for. He’s written emulators for everything from the humble Acorn Electron to the StrongARM-ed Risc PC with Spectrums, Amstrads, Beebs, Archimedes and much else in between.

Elkulator, running on Fedora 14

So it wasn’t altogether surprising when, last month, Sam asked if I could create some icons for his desktop he could use with Tom’s emulators.

Superior's EGO:Repton4, running on RPCEmu

Sam is a KDE desktop power user, whereas I’ve always been a GNOME numpty. Fortunately for us starving scribblers and colourers in there is a project that aims to standardise all free software desktops and ensure we can create icons once that look good on all of them. The project is called the freedesktop project and the part concerning icons is called Tango.

There are numerous tutorials on the web that explain how to create Tango icons in both Inkscape and The GIMP.

The first icon I tried to create in Tango format was the three dimensional RISC OS era Acorn logo, to use with Arculator. Below, you can see the real Acorn logo on the left, and the “Tango”-ed version on the right.

More Tango-ed than Judith Chalmers

As you can see, the Tango version looks rather cartoonish – and the colours are rather muted and pastel. And the direction of the light source has been changed. This was all done deliberately and in order to follow the Tango guidelines.

Sam was happy with this icon and asked if I could create icons for all of the Acorn-related emulators. And that’s when sticking to the rules started to get a bit of a pain. For Tango icons, each icon should be a distinctive shape in order to help those with poor eyesight and each icon should also contain a metaphor as to the icon’s purpose.

However, for the emulators all that we really needed was a square icon with a logo that told you at a glance what computer you were using so the guidelines rather went out the window. The Tango colours were also very restrictive as far as what I could use so I just threw caution to the wind and did what I felt!

Here’s the Elkulator icon:

I really like the background grid, which was the trademark of the Acorn Electron.

Here’s the B-Em icon:

And here’s the RPCEm icon:

I also created some Archimedes artwork – here's the Archimedes logo I created as an SVG file in Inkscape:

Click to enlarge.

Here it is “Tango”-ed!

And here are the full set of icons I created for Sam:

Click to enlarge

In future, when I have more time, I’ll create proper Tango themed icons for all of these emulators. I spent about two minutes on each of the icons above and it shows! This will require me to actually draw the systems being emulated and make sure that I've got a different shaped outline for each one.

So I'll probably return to this topic when I've done some decent, real, Tango icons!

Jewel Chase In A Jewel Case

Thanks to Dave Moore at Retro Software, I received a very exciting package in the post last week:

It seems so strange to go from a sketch on an envelope, to producing artwork in Inkscape to a finished product on my shelf with a 5.25" floppy inside.

If you want to get hold of your own copy of Repton: The Lost Realms, it is available here.

Coloured Sugar

Once I'd finished writing a range of BBC Micro Python-Fu image filters for The GIMP, the Amstrad CPC series seemed the obvious next computer to tackle.

The graphics capabilities of the CPC were very similar to those of the BBC Micro, but the CPCs benefitted greatly from having many more colours available. Everything you could ever want to know about the video capabilities of the Amstrad CPC range is explained here.

The graphics capabilities are so similar, in fact, that to create a graphics filter for Amstrad CPC in Mode 0 all I had to do was change the palette data in my BBC Micro Mode 5 filter. Instead of picking 4 colours from a range of 8 the filter simply needs to pick 16 colours from a range of 27.

So, here is a picture of Baron Sugar's beloved Hackney Empire (formerly the ATV Television Theatre):

ATV, Rediffusion and ABC all made programmes here

And here it is put through my Amstrad CPC Mode 0 image filter for The GIMP with no dithering:

Amstrad CPC, Mode 0, No Dither

Oh dear. Even the BBC Micro Mode 2 filter seemed to be able to do better:

BBC Micro, Mode 2, No Dither

Here's the Amstrad CPC Mode 0 filter with 2x2 threshold matrix:

Amstrad CPC, Mode 0, Ordered Dither 2x2 threshold matrix

The BBC Micro Mode 2 version with a 2x2 threshold matix seems much flatter and less detailed:

BBC Micro, Mode 2, Ordered Dither 2x2 threshold matrix

So what went wrong with no dithering? Well, the method I'm using to choose a palette is very crude - it picks the sixteen most used colours from the Amstrad CPC palette to go into the final image. If my method is applied an image with lots of dark areas and a few highlights the highlights will be completely missing as the light colours will not be used enough to feature in the final table of 16 colours. I obviously need to find a method that takes into account the range of luminance used on an image.

The situation gets even worse when dealing with the Amstrad CPC Mode 1. Amstrad CPC Mode 1 is very similar to the BBC Micro's Mode 1. But whereas Mode 1 on the BBC Micro can pick 4 colours from a selection of 8, Mode 1 on the Amstrad CPC can pick 4 colours from a selection of 27.

Here's a picture of Polly parrot:

Pining for the fjords

Here's the same picture put through the Amstrad CPC Mode 1 filter with no dithering:

Amstrad CPC, Mode 1, No Dither

Here's the same picture of a parrot put through the BBC Micro Mode 1 filter with no dithering.

BBC Micro, Mode 1, No Dither

Even Sierra3 error diffusion won't help the Amstrad CPC Mode 1 image:

Amstrad CPC, Mode 1, Sierra 3 Error Diffusion

Whereas the BBC Micro filter produces excellent results:

BBC Micro, Mode 1, Sierra 3 Error Diffusion

Needless to say, the Amstrad CPC filters should be producing better results than the BBC Micro filters!

So, I'm going off to find a better way to pick an Amstrad palette! In the meantime, if you want to play with the Amstrad CPC filters they can be downloaded from here. Microsoft Windows users can find out how to install and use the filters with The GIMP by following the very nice set of instructions with pictures I've found here.

A la Mode

Time for another chapter in the continuing story of producing Python-Fu retro computing image filters for The GIMP from some original programs in sdlBasic by nitrofurano.

In my last post I talked about ordered dithering, and how it compared to the error diffusion technique I had implemented previously. After successfully implementing ordered dithering the natural next step was to incorporate the ordered dithering into my BBC Micro Mode 2 image filter so that all the image processing techniques were available in one filter.

Finished filter interface

Whilst doing this, I also made the Strength slider in my BBC Micro filter act upon Ordered Dithering as well as Error Diffusion. This allows for some quite interesting effects.

Here is John Liven's Somerset cottage picture. I've applied Ordered Dithering with a 2x2 threshold matrix set to 100% strength:

Mode 2, 2x2 Ordered Dither, 100% Strength

And here is the same picture with the same dithering applied at just 50% strength:

Mode 2, 2x2 Ordered Dither, 50% Strength

Once this was done the BBC Micro Mode 2 filter was finally finished off. I then turned my attention to writing a BBC Micro Mode 5 filter. Mode 5 is very similar to Mode 2, but you can only use 4 colours from a selection of 8.

This means the image filter needs an additional step in which the palette to use for the image is selected. The way I approached this was to scan the entire image pixel by pixel tallying which of the 8 possible BBC Micro colours each pixel was closest to. Then, I simply used the four most commonly found colours.

Incidentally, the way you work out how close one colour is to another is quite simple once it's explained to you: I found the answer here.

After a coding a bit of Python I loaded an image of some parrots into The GIMP:

Norwegian Blue is on the left

And tried out the filter with no dithering. It worked first time:

Mode 5, No Dithering

And when some Sierra3 error diffusion was added too, the results were incredibly good:

Mode 5, Sierra 3 Error Diffusion 100% Serpentine

I still can't get over the fact that there are just four colours (black, white, red and green) in this image.

With a Mode 5 filter under my belt it was very easy to produce a Mode 1 filter. Mode 1 is the same as Mode 5, but has square pixels:

Mode 1, Sierra 3 Error Diffusion 100% Serpentine

And a Mode 4 filter. Mode 4 is like Mode 1, but is restricted to just two colours:

Mode 4, Sierra 3 Error Diffusion 100% Serpentine

So, I have got a pretty nice suite of BBC Micro image filters, with only Mode 0 to add. As always, you can download them from here. Microsoft Windows users can find out how to install and use the filters with The GIMP by following the very nice set of instructions with pictures I've found here.

What A Ditherer

I've spent a lot of time recently converting nitrofurano's sdlBasic retro computing picture converter programs into Python-Fu image filters for The GIMP. I've also been adding a few ideas of my own - particularly in the area of half-toning techniques.

After successfully getting Error Diffusion working, I decided to see if I could get Ordered Dithering working. Ordered Dithering is a technique akin to the half-toning you see on images in newspapers. From an image made up of many colours you can create an image made up of only a handful of colours stippled such a way as to give the illusion of many colours.

There are several excellent explanations of Ordered Dither on the web for the curious written by people who actually know what they are talking about - I would recommend this one and this one.

Ordered Dithering is much simpler than Error Diffusion (which is probably why it took me longer to get it working!). As it's a much simpler process it's lightning fast in comparison, even when coded in Python.

As a test, I took John Liven's picture of a Somerset cottage. 

Photo: John Livens

Then I converted the image to the BBC Micro's MODE 2 (which has just eight colours) using an ordered dither with a 2 x 2 threshold matrix.

BBC MODE2, Ordered Dither, 2x2 matrix

As you can see above, it produces a very pleasing regular patterning on the colours - to allow you to compare, here is the same image with Floyd-Steinberg Error Diffusion:

BBC MODE2, Floyd-Steinberg Error Diffusion

On a small image such as this, larger grids don't really add much. Here is an ordered dither using a 4 x 4 threshold matrix:

BBC Micro MODE2, Ordered dither, 4x4 matrix

But, the proof of the pudding is in the eating. If you have The GIMP installed on your computer you might like to try the ordered dither filter for yourself - it's available from here.

BBC on the BBC

Over the past few days I've been converting nitrofurano's image filters from stand-alone sdlBasic programs to Python-Fu image filters for The GIMP. But, so far, there has been a particularly noticeable absence - the BBC Micro.

Partly that was because the BBC Micro world has already been utterly spoilt in the image conversion department by Francis G. Loch's incredible BBC Micro Image Converter. It's a highly professional piece of software and does it all. I've posted about it many times here and the work I've done for Retro Software would have been utterly impossible without it.

BBC Micro Image Converter by Francis G. Loch

But partly it was because Francis' program had inspired me to try and find out more about the mind-boggling array of dither options he had included in his program. It boasted a host of exotic sounding names like "Floyd-Steinberg", "Sierra", "Jarvis, Judice and Ninke" and "Stucki".

Paulo had used a technique called Bayer ordered dither in his filters, which is similar to the traditional half-toning used in print. It's very powerful, very fast and gives you a lovely regular patterned effect on the images, which is sometimes just what you're after.

Naturally, Francis' BBC Micro Image Converter does this as well. But these exotic sounding names were the inventors of various flavours of another technique: error diffusion.

Error diffusion works by trying to compensate for the colour information lost by turning a pixel into a value from a restricted palette by sharing it out amongst the surrounding pixels.

After looking at the Wikipedia entry for Floyd-Steinberg, it looked like even I could understand how to program it and then after finding an excellent article here I realised that all the other filters did exactly the same thing. They just shared out the lost information (or quantisation error) to different pixels in different proportions.

And, after a couple of hours messing about in Python, I managed to get out a servicable MODE 2 image (click on the images to enlarge):

Floyd-Steinberg error diffusion, 100% strength

You can see just how effective error diffusion is when you compare the results to the same image processed with no error diffusion:

The same image with no error diffusion

Here's the original image for comparison:

I'm the one on the right

I excitedly added a range of different filters into my BBC Micro image filter:

Take your pick!

There was a problem though. Sierra3 was taking well over 70 seconds. This sluggishness was caused by the inefficient way in which I was checking that a pixel was within a certain range in Python.

Sierra3, 100% Strength - and very slow!

An error message I had been getting during development rather ironically proved to be the key to solving the speed problem. Instead of using time consuming range() functions to see if pixels were inside a particular range, I could use exception handling and check for an IndexError instead. This was very fast - it sped the filter up by a factor of at least four. Mind you, it still crawls along compared to Francis' version!

The next thing I needed to add to the filter was something called "Serpentine parsing". This means that instead of processing the image from left to right as it moves down, the computer processes the image backwards and forwards. This helps to stop all the error diffusion going in just one direction - smearing all the errors to the right.

Finally, pinching another one of Francis' excellent ideas, I added a strength control to the filter to allow you to control how strongly the error diffusion works.

Finished interface

Here is Test Card F with 50% Floyd-Steinberg error diffusion strength:

Floyd-Steinberg error diffusion, 50% strength

And here it is with 25% Floyd-Steinberg error diffusion strength:

Floyd-Steinberg error diffusion, 25% strength

So, a BBC Micro Mode 2 image filter for The GIMP, that can be downloaded from here. However there are numerous refinements that need to be added to it. But they will have to wait for another day.

Test Card F Copyright © 1967 BBC, ITA and BREMA.

Designing Repton's Lost Realms

If you've been here before, you'll probably already know that this year is Repton's 25th anniversary. And, as part of the celebrations, Retro Software is releasing Repton: The Lost Realms for the BBC Micro and Acorn Electron.

I've already blogged about creating the cover artwork and the loading screen for the game. However today is the 6th November and Repton: The Lost Realms is being officially launched at R3PLAY in Blackpool. That means I can at last talk about creating the graphics for the game itself.

My cover artwork

I was first approached by Dave Moore about contributing to Repton: The Lost Realms in mid 2008. Peter Edwards had just recovered a load of my old Repton 3 and Repton Infinity screens from some of my 5.25" floppies and the graphics in them had impressed Peter and Dave enough for them to ask if I would be interested in creating some screens and graphics for Repton: The Lost Realms.

Like Repton 3 before it, Repton: The Lost Realms is a game that allows you to not only edit its levels, but also redefine its graphics. That means that it's possible to provide a selection of different screens and graphics for players to load into the game.

Lost Realms as I first received it

At this stage, the Repton: The Lost Realms came with only one set of screens. As you can see above, it used the Repton 3 graphics with a few additional graphics for the game's new elements designed by the game's original programmer Paras Sidapara.

As there were to be four sets of six screens included in the game, my first idea was to theme each set of graphics around the existing Repton releases. In other words, have a Repton 1 set...

Repton 1 Lost Realm

...a Repton 2 set...

Repton 2 Lost Realm

...a Repton 3 set...

Repton 3 Lost Realm

...and a new set for the final set of screens.

I quickly hacked about and transferred the graphics from these games into Repton: The Lost Realms. At this stage I was designing new characters in the Repton Infinity graphics editor (Film Strip) and then transferring them over to Repton: The Lost Realms by transferring blocks of data between files using the BBC BASIC command line.

Film Strip - An excellent graphics editor

The reason why I preferred Film Strip was that it was designed for use with a keyboard. I didn't have a real BBC Micro to use so I was using these programs via the excellent emulator BeebEm. In fact, as at that stage there wasn't a native GNU/Linux emulator for the BBC Micro at the time, I was using BeebEm via WINE.

The Repton 3 and Repton: The Lost Realms editors had adopted the then very fashionable WIMP paradigm. However, using a WIMP interface with a keyboard is very hard going and I found the AMX Mouse option tricky to get working in BeebEm. That meant I couldn't use these editors with my mouse.

Another problem I had with Repton: The Lost Realms' editor was the awful yellow and black colour scheme used for the editor's pointer. It was probably the worst colour scheme you could have picked if you want to design graphics precisely - the outline of the pointer gets lost against black, but most of the graphics have black backgrounds or outlines!

Repton: The Lost Realms' Editor

After I had designed Repton 1 and Repton 2 themed graphics it soon became obvious that this approach would not work. There were various new elements in Repton: The Lost Realms that were not present in previous Repton games. I wanted to redesign these in each set to match the style of previous Repton releases. However Dave wanted to keep the new game elements that Paras had designed looking the way Paras had designed them. However this would have looked out of place, particularly in Repton 1 which is quite abstract and geometrical in design.

Therefore, after talking it over with Dave and Paras we decided it would be best if I design four completely new sets of graphics for the game, bearing in mind the need to keep the original design of Paras' new game elements in each set. We would also only vary the game characters that varied in the sets of screens supplied with Repton 3: namely the walls, eggs, monsters and crowns.

I had a few ideas for the graphics having got used to playing the game. I didn't think that the inverted cage colour scheme for the anti-clockwise spirits worked at all. I needed to find a way to make these cages look a little less incongruous. I wanted to make the graphics look 1988-ish - so I used the style of later BBC games like Richochet and Star Port as inspiration. And I wanted to use stippled colours as much as possible to make the apparent colour palette seem more than the four colours that the game was limited to.

I designed the set of graphics for the final set of levels (PRESTO) first. My inspiration for these were the full-page adverts for Repton 2 and Repton 3 that Superior Software used to run in Acorn magazines at the time. In particular, I wanted to design a set with light mortar between distressed bricks. I'm very proud of this set and I think it's actually my favourite.

Presto - not for the faint hearted

I got a bit carried away, and I also redesigned Repton to look like he did in Superior's adverts - this was very quickly and firmly rejected, and rightly so!

My Redrawn Repton went down like a cup of cold sick

I had one set down, three more in front of me and even using FilmStrip on a BBC Micro emulator seemed like very hard going. I really wanted to use The GIMP to design the graphics and suddenly it dawned on me that I could.

I could design the graphics in The GIMP and then transfer them to the BBC Micro emulator using the BBC Micro Image Convertor by Francis G Loch. This is an application written in PureBasic that takes image files (bmp, jpg, etc.) and downconverts them into the native screen display formats of the BBC Micro.

The process has a few stages. First I design all the graphics as separate files in The GIMP:

Completed graphics designed in The GIMP

Then I use the GIMP to slice them up and put them in rows:

Sliced and Diced in The GIMP

And finally I convert the graphic into BBC Micro format using the BBC Micro Image Convertor:

And converted to BBC Micro format

So, I fired up The GIMP and the next set I designed was for the LARGO set. This is the default set that loads when the game or editor loads, and the levels in this set were the original six levels designed by Paras Sidapara back in 1988.

Largo - the Realm of the Exile

Because I knew Paras was a huge fan of the game Exile, I decided to base the design of the walls on the walls found in Exile. This set looked very nice and thanks to The GIMP I was able to design them very quickly.

Adagio - Exile crossed with Repton 2

The third set I designed was a set for the ADAGIO screens. This set was a kind of cross between the walls found in Exile and the walls found in Repton 2 (my favourite Repton release). It didn't work as well as I would have liked and I wish I'd done something a bit different.

Allegro - juicy, apparently...

The final set I designed was the ALLEGRO set. It was loosely based on the graphics for the game XOR, which my children were madly into playing at the time. This set has been described as looking "juicy", whatever that means! Dave Moore accused me of taking a little more care over these graphics than some of the others because I knew I was designing all six levels to go with them. How very dare he!

The work on the graphics Repton: The Lost Realms was very straightforward. I did very little rework once we decided on what we were doing and there were only two real debates about the game characters. The first concerned earth, the second concerned fungus.

As far as the earth is concerned, I wanted to experiment with some dense Ravenskull style earth, whereas Dave Moore preferred the very sparse earth used in the Toccata level set of Repton 3. Dave got his way on that one!

Now that's what I call fungus!

The fungus debate concerned my preference for fungus that looked like a toadstool rather than the amorphous mould that was presented in Repton 3. In the end, I redesigned the fungus to look slimy rather than mouldy but it's probably the graphic I am least happy with.

Now that's what I call fun, Gus!

We also had a discussion about the "freeze pill". This was a green pill that froze monsters temporarily. What with absorbalene pills and time pills I thought Repton's drug habit had gone far enough.

Freeze pills - just say no.

 
I wanted to replace it with a Citadel style snowflake. Everyone agreed, and that also involved making changes to the editor and game map graphics which I did by hacking the code about. But, although my snowflake was a good idea, I think the graphic I designed was horrible.

Snow flake - just say yuck.

Once I'd designed all four sets, I thought that that was that - only it wasn't. By this stage Tom Walker (someone for whom the word genius seems utterly inadequate) had joined the project, and had started work coding an Acorn Electron version.

The Acorn Electron is cruelly afflicted in many ways, but one of the worst is that it has no hardware scrolling. That is terrible news for a game like Repton which relies on scrolling. Acorn Electron scrolling has to be done in software, which eats up the memory available for the game - and its graphics. The graphics in Acorn Electron Repton: The Lost Realms are 12 x 24 instead of 16 x 32 for the BBC Micro version.

Skull (Acorn Electron)

This meant I had to create cut down versions of all of the games' graphics for the Acorn Electron version, and doing this took as long as it took to create the original graphics. In fact, I put in so much effort I actually prefer some of the Acorn Electron graphics.

Largo - All ready to transfer to Elkulator

Probably the most interesting thing about doing this was the lack of an Acorn Electron editor - or indeed an Acorn Electron version of the game itself! I had actually finished the graphics and put them in game files before Tom had finished coding the Acorn Electron version of the game.

It was quite some time after I had finished the graphics that I was actually able to play with the graphics in the game itself via Tom's excellent Acorn Electron emulator Elkulator.

 Acorn Electron version

Keen eyed Repton fans will notice that Acorn Electron Repton: The Lost Realms reintroduces Tim Tyler's Repton sprite from Repton 2. I think this has much more personality than the one used in Repton 3.

I knew that there was a keen interest in the Repton: The Lost Realms from Acorn Electron enthusiasts so I put an enormous amount of effort in the graphics for the Electron version - I just hope they like them!

And finally -  a word about the design of the crowns. I spent many years living in my wife's home-town of Mélykút, the birthplace and home of the legendary restorer Szvetnik Joachim. He was famous for supervising the return of the Holy Crown of Hungary from the USA in 1977. I went to his workshop in Mélykút to translate for some tourists from New York State, and enjoyed my visit so much I decided to make the crown in ALLEGRO look like the Holy Crown.

Allegro Crown (BBC Micro version)

The other crowns in Repton: The Lost Realms are also based upon real crowns - I wonder if you can work out which ones?