This is a quick little patch that fixes a bug in the JPEGRender module.
It's aimed at pre-RiscPC users, but non-StrongARM RPC users may find it useful as it allows slow dithering of JPEGs to be disabled, speeding up screen redraw by a factor of about 3 in 256 colour modes (at the expense of a little quality, of course :-)
This patch is essentially the same as David Thomas' patch for SpriteExtend 0. 99, but implemented as a little application to be put in your boot sequence (!Boot.Choices.Boot.Tasks would be a good place).
You can run it at any time if you want to just test it...
I recommend that you test the patch in this way whilst there's nothing important loaded - it might all go horribly wrong :(
Whilst I was fixing this up, I thought it might be nice if it was possible to disable the error-diffused dithering the module is capable of using (it's about a third to a quarter the speed of the normal dithering :-)
The new browser uses error-diffused dithering which is slow, even on my RPC :-( so I dread to think what it's like on ARM3 machines.
I've made the patched module supply a *Configure keyword
JPEG_FastDithering.
By default, the full error-diffused dithering is enabled.
To disable the slow error-diffused dithering, press f12 (or start a
taskwindow, or whatever) and type:
*Configure JPEG_FastDithering 0
To enable slow error-diffused dithering, the command is:
*Configure JPEG_FastDithering 1
NB: This setting is not stored in the machine's CMOS RAM. If you want to have slow dithering turned off every time you boot up, add the *command to !JPEGPatch.!Run
!JPEGptch Version 1.00 (9 Nov 1997)