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How to convert images for TMS9918A graphics on the RC2014

For me, graphics capability is essential for an 8-bit computer. My graphics chip of choice for the RC2014 is the very capable TMS9918A.

It has 15 colours, sprites, several modes and a max resolution of 256x192. It makes arcade-style games possible, such as Tut-Tut above. 

I enjoy simply displaying images and have a bunch on my CF card (my 'hard drive') and have written image viewer and slideshow apps to display them.

Some useful links:

Image conversion

I did dabble in writing my own utility to convert .png images but then settled on the Multipaint app which can open a png in a MSX 'screen 2', allow you to tidy it up with paint tools and save as a .sc2 file.

(An sc2 file is little more than a video-memory dump and so it's easy to blast that back into vram to display the image. See my sc2view utility.)

More recently, a friend told me about Convert9918, which is a Windows exe but runs very happily for me under Wine on a Mac. (I can't comment on using it on Linux).

Using Convert9918

It's easy to just drag an image onto Convert9918's window. I've found it an advantage to crop the image to an exact 4x3 aspect ratio first to avoid black bars. You'll want to select 'Bitmap9918A' from the options at the bottom. 

There are plenty of settings to play with. The above conversion uses no dithering, the one below uses 'order 4'. After changing a setting you need to press Reload to see the changes.

The source image here is monochrome, but as you can see, the utility uses the colour palette. I'll come to black and white in a second. 

'Posterising' the image, or starting with an already-posterised image (such as Phil Lynott below) works really well and can remove the need for dithering. This is a filter that's available in various paint programs which removes subtle colour gradations down to a few hard-edged colours.

To save the image, hit 'Save Pic' and then choose 'MSX SC2' as the output format. Choose a filename with up to 8 characters, the .sc2 will be added automatically.

Convert9918 is capable of converting an image to the ultra low-res full multicolour mode (64x48) but it's hard to find an image that converts well. Another option that is well worth playing with is the 'B&W bitmap', which is the same resolution as the .sc2 but uses just two colours. This can be very effective with a good choice of dither.

For further reading, harmlesslion, author of Convert9918 has published this rundown of the available options.

Displaying .sc2 images on an RC2014


There are a couple of video module options. Above is the TMS9918A module designed by J B Langston. This is open-source and I've been building and supplying these with his permission, initially as part of my MSX2014 project.

It is a real DIP-package chip and they are available unused. The output is composite. It's not pin-sharp and has artefact colours (at least with the displays that I use.) You still have to use some kind of terminal because it doesn't handle the serial output of the CP/M operating system.

As an alternative, this is my TMSEMU module 

It uses a microcontroller but I've disguised that to some extent. It has DVI (HDMI) output which is sharp and vibrant.

It's compatible with software written for the original TMS9918A module but in addition it listens to the serial line and uses its 40-column text mode on startup, so you can use CP/M or SCM to load and start your program. 

As mentioned, my SC2VIEW.COM will open a .sc2 file, see the screenshot above. SLIDESHW.COM will show a slideshow of all .sc2 files in the same directory/drive letter.

For 32k machines without storage, you will need to build an app which contains the viewer code and the .sc2 binary.   

Here are photographs of the earlier conversions, complete with moire effect (not visible in real life). Then some more of my favourite conversions.













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