Mark Goodge wrote:

> The problem is likely to be that you originally created them on a Mac
> and saved them with Mac byte order. That's why a Mac can see them but
> a PC can't. Using GraphicConverter to "save for the web" has saved
> them with what the Mac calls "Windows" byte order, but everywhere else
> (including Linux) just calls "normal" :-)
> 
> Mark


I've never had problems saving jpegs on this machine (Sun Blade 2000), 
and like a Mac, its UltraSPARC processor it is big-endian, rather than 
the little-endian of an Intel or AMD based PC.

I might be wrong, but I suspect the byte ordering is defined in the JPEG 
standard and not left up to different CPUs to write data in a different 
way. I know this is the case for BMP, but I don't know for sure on JPEG.

On Mon, 21 Apr 2008 21:45:32 +0100, Dave put finger to keyboard and
typed:

>Mark Goodge wrote:
>
>> The problem is likely to be that you originally created them on a Mac
>> and saved them with Mac byte order. That's why a Mac can see them but
>> a PC can't. Using GraphicConverter to "save for the web" has saved
>> them with what the Mac calls "Windows" byte order, but everywhere else
>> (including Linux) just calls "normal" :-)
>
>I've never had problems saving jpegs on this machine (Sun Blade 2000), 
>and like a Mac, its UltraSPARC processor it is big-endian, rather than 
>the little-endian of an Intel or AMD based PC.
>
>I might be wrong, but I suspect the byte ordering is defined in the JPEG 
>standard and not left up to different CPUs to write data in a different 
>way. I know this is the case for BMP, but I don't know for sure on JPEG.

Strictly speaking, there's no such thing as a "JPEG" file per se. JPEG
is a lossy compression method used to produce data which is then
encoded into a file. The file format commonly described as JPEG (and
usually named with a .jpg or .jpeg extension)  is more correctly known
as JFIF (JPEG File Interchange Format). JFIF itself comes in several
variants, and some of these can include data which follows the
system's native endianness instead of being consistent across
platforms. Photoshop in particular is prone to creating
natively-endian image files on a Mac as it encodes a lot of additional
data (some in EXIF format, which is theoretically incompatible with
JFIF but can be kludged into the same file, and some in its own
proprietory encoding) that isn't part of the base image data. And that
in turn is because Photoshop was originally a Mac application (ie,
designed for the Motorola chipset rather than IBM/Intel), and file
interchangability with PC applications was an optional setting ("save
in Windows byte order") rather than the default. 

Mark 
-- 
Stuff, some of it good, at http://www.good-stuff.co.uk 
"All the promises we break from the cradle to the grave"