Section 9: Technical Details

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Q9.1) How do I get a faster interrupt timer than the centisecond ones?

For this you require the use of IOC Timer 1, a 2MHz timer unused by RISC OS
and claimable by code for use. Details of how to program the timer are
available in the IOC datasheets, or you could look for various PD utilities
like TimerCtrl that handle the timer for you.

I am informed that the Acorn TimeCode system now lays claim to Timer 1 and
that software using it is deprecated.

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Q9.2) How can I create Interlaced GIFs on Acorn machines?

Four utilities exist to let you create these.

spr2gif will take a sprite and convert it to a gif file. It will interlace
and render transparent the gif as well. For the transparency it uses the
colour of the first masked pixel it encounters in the sprite - suitable for
automated gif image creating. (No need to twiddle with specifying
transparency colours.)

WebGIF allows you to add transparency and interlacing to your GIFs as well.

Creator, from about v2.00, can create interlaced GIFs. However you have to
specify the transparency colour directly.

And finally InterGIF not only can create interlaced, transparent GIFs but is
capable of creating animated ones as well.

On top of these utilities an increasing number of commercial programs can
create Interlaced GIFs, Photodesk being a prime example.

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