aliensrcooluk at yahoo.co.uk
Mon Jun 25 16:30:30 CDT 2007
Jules Richardson <julesrichardsonuk at yahoo.co.uk> wrote:
> Andrew Burton wrote:
> > Hi, i was reading up on bitmap (mainly .bmp, with
> > some .wbmp) images
> > last night and was wondering why everything is
> > stored backwards
> > (e.g. BGR instead of RGB and the bottom of the
> > image first, instead
> > of the top)?
> I believe the backwards RGB quads* are just a
> hang-up from the fact that
> almost every platform which supported .bmp files
> used an Intel x86 (or
> compatible) CPU - and Intel's x86 processors store
> multi-byte values lowest-first.
Yeah, I discovered that out the hard way. Do all Intel CPU's do that or just x86's (and compatibles)?
> *Going from hazy memory, I seem to recall that
> colour map entries in .bmp
> files are four bytes: BGRx, with x being always set
> to zero. I can't remember
> if 24-bit direct-colour images also use four bytes per
> pixel or only three.
Yeah, that's exactly how it works. I assume the reserved bytes (always set to 0!) were to do with aligning values on a 4 byte boundary for the Intel X86?
Not got onto 24-bit images yet.
> No idea why the origin of the image was bottom-left
> rather than top-left, but
> there wasn't ever really a standard for this kind of
> thing (if MS Windows
> itself sets the origin at bottom-left then it certainly
> makes sense; .bmp was
> really only ever popular for MS-Windows, after all)
> > Also would i need to pay a license if i wrote a
> > program to create .bmp
> > files?
> As far as I know, no.
Ok, thanks. Will check online just to be safe :)
> > My main aim is to write a .bmp to (amiga) .iff
> > format
> Heh, the last time I wrote any .bmp handling code it
> was to do that the other
> way around, as I had a bunch of IFF files that I
> wanted to read on a Windows
> 3.1 box.
> > , but would love to add
> > full .bmp support to an art program i wrote for the
> > amiga and then stick it
> > online (on Aminet.com ) for other people to use if
> > they wish.
> Obvious question: why .bmp? As above, it was only
> ever popular with MS
> Windows; in the rest of the world TIFF, PCX, or
> Targa support tended to be a
> lot more prominent. PCX and Targa seem to have
> fallen by the wayside these
> days, but TIFF is still alive and well, and of course
> PNG has come on the scene.
I have some TIFF and PCX images on old PC disks (from early 90's). Microsoft Paint doesn't support them (I don't require a proper art program on the PC for what I do) and I doubt the vast majority of PC users have even heard of them.
I got WinCapture, made around 1993, off of one of the old disks and it still works (just about) on Windows 2K. I can use it to capture any image onscreen (except movies read from CD/DVD - I guess because the software is so old?) and turn it into a bitmap image :)
> If I were writing something to export data to an
> image format these days, I'd
> pick TIFF or PNG over MS-bitmap; certainly writing > a TIFF encoder isn't too
> complex (writing a comprehensive decoder can get a > little hairy due to all the
> vendor extensions, but writing something to handle
> the typical flavours isn't
> hard), and from what I hear PNG isn't too difficult to > handle either.
Well, like I said the main target is Amiga .iff format, but it would be nice to include other formats for those using Amiga emulators. That way they can transfer images to a PC friendly format for whatever purpose they require them for (website, advert, project, etc.).
It would make advertising my games on my website easier if I can get direct images, instead of using a webcam or digital camera to take pictures of the screen (which turn out rubbish - see http://www.geocities.com/aliensrcooluk/mysite/glists/my_amigagames.html )!
I haven't actually got pictures of GamesVol3 up yet, though it only contains my .ABI encoder and decoder programs. Yes, I created my own image format!
For "simple" images it does turn out smaller than the Amiga .iff format, despite me not using compression in version 1! I do include example images on GV3.
None of my stuff is actually available online yet, I just sent disk-based copies to 2 fellow AMOS coders - one in Germany and one in the US.
Err... I'm babbling now. Better finish up and read the rest of my emails :)
aliensrcooluk at yahoo.co.uk
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