There are many image formats about - hundreds, to be precise. This is a pain,
if you want to load an odd format. Or maybe you want to be able to easily
create Jpegs (a highly compressed, high quality format), to store your images
with a minimum of hard disc space.
Spr2Jpeg is the answer.
Sprite 2 Jpeg is an image converter, which allows you to convert sprites to Jpegs, and back again. It also accepts and outputs Clear files, GIFs, Targas, and it can handle full colour sprites, on recent machines. It doesn't display
images, however.
Load in the normal manner. Note that ChangeFSI haveing been 'seen' is a Good
Idea.
Operation is pretty simple. Drag an image file onto it's iconbar icon. A save
box will appear, as per Risc OS standard, with one exception, to wit:
At the bottom of the box is a little format selector, with a pop-up menu icon.
Click here to select the output format. Then save as normal. You'll note that
Jpeg files may be saved as anything (except Jpegs...duh :-), but anything else
will only save as a Jpeg.
Anything other than Jpeg <---------> Jpeg
in other words.
Options
=======
Yep, gotta have options. Loads of them. Don't understand half of them myself,
but never mind. Click on the iconbar to get the options window.
It's divided into two halves: Compression (making Jpegs) and Decompression,
for decompressing Jpegs.
Compression options are:
Quality: Trade of image quality against file size; the lower the number, the
smaller the file. Anywhere between about 60-95 is reasonable; higher
is inefficient, lower is starting to degrade image quality.
Experimentation is the order of the day (range 0-100)
Optimise file size: Takes a bit longer to compress, but makes a smaller file.
Decompression time is the same. I can't tell the time difference,
anyway. Leave on, is my advice.
Grey-scale: Makes the image grey-scale. Jpeg file is slightly smaller, but
unless the image is already grey-scale, I'd leave it in colour. You
can always grey-scale it at a later date.
Smoothing: Smooths the image; again, range from 0-100. Sometimes useful, but
as I tend to use Jpegs for storing images, I'd rather smooth them
as and when I want to use them; hence I'd leave it off.
Other options: Less important options:
DCT method: I don't know what DCT stands for, but it's a speed / accuracy
trade off. Integer, the default, is fine (as is Fast): Floating point,
the most accurate is slow without an FPA chip, and I can't tell the
difference anyway.
Debug: Useless, but there for completeness. Tells you a little about what's
happening.
Arithmetic coding: Could be implemented in later versions, though this isn't
likely, as it is not supported for "legal reasons". I've never come
across this format, anyway. It's just a different method of making
the Jpeg.
Non-interleaved: Not yet supported. Maybe soon...
Extra: There are a few ultra-nerdy type options which require you to be a
rocket scientist to use them. You could put them here, if you knew
what you were doing. Example: type in
-debug
in the box, to enable debugging. Mainly to allow you to use later
versions of the compressor with this front end.
Decompression options:
Cross-block smoothing: Improves the image at very low quality settings (10-20)
May make the image worse at normal settings; quite memory intensive.
Grey-scale:Output a greyscale image.
Debug: As compression.
Fast: Fast, low-quality output.
DCT: As above.
Dithering:Trade off speed against quality with dithering. Floyd-Steinberg is
best, none is fastest.
Quantize:Reduce to maximum n colours. Don't use this switch if creating
sprites, as ChangeFSI will do a better job. You might need to use it
if you wanted to reduce the image to 573 colours (say), for some
strange reason. Normally, not excessively useful.
Scale: Scales the image. Again, use ChangeFSI in preference to this.
Extra: As above.
Use Cancel, Save, OK, to do just that to the options. Adjust on OK will bring
the options into effect, but keep the window open.
Miscelanea
==========
Spr2Jpeg will not work with ArcFS archives. Don't ask me why, I can't work it
out. If you do want to use ArcFS, you'll have to just take the image out of
the archive to start with, Spr2Jpeg-ify it, save to a normal filer window, and
shove it in an archive. Sorry.
Spr2Jpeg is Freeware, not that that has any legal significance in this
country, but basically what that means is that you are more than welcome to
copy it and pass it around, so long as you don't change any of the files.
Spr2Jpeg is not garanteed in any way; Neither I the author, nor the Independent
are responsible for any major alien invasions, loss of self-esteem, or anything
else arising from the use of Spr2Jpeg.
Which is not to imply that it will go wrong, of course.
Interesting tip: reduce quality to about 3, which will give a very strange
image, which can't be recognised normally. Then squint at it, and it's quite
incredible the amount of detail your brain can fill in. Wierd.
Thanks
======
This software is based in part on the work of the Independent JPEG Group: so
thanks to them for writing the compressor / decompressor.
Dave & Sue McCartney of the Datafile, the best PD library in town.
Doggysoft, for the WimpExt module.
Acorn, for ChangeFSI.
Whoever invented chocolate.
I probably ought to say: "The Graphics Interchange Format(c) is the Copyright property of CompuServe Incorporated. GIF(sm) is a Service Mark property of CompuServe Incorporated." as well here. Well, there you go.
The Author
==========
David Rodgman
Laurel Farm
Upper Strode
Winford
Bristol
BS18 8BG
Let me know if you have any problems with Spr2Jpeg, bugs etc. etc. or just have
really huge amounts of cash you need to get rid of quickly.
