While it's true that a file in memory "doesn't really have a type - it's in
whatever internal format the software that opened it uses (perhaps just an
array of pixel values)" it's important to remember that those pixel values
are the values that have been read from disk file (or scanner), and include
only the JPEG encoded 'lossy' picture data. Even though the pixel count may
be 18MB, you will not get 18MB of image data from a 1.2MB JPEG file. You may
not notice the difference in an ink-jet print at the desired size, but in
the case of printed illustartions in a publication, I suspect that there is
a risk the process of 'screening' the image for printing could magnify the
file-compression artifactts.
Piers
-----Original Message-----
From: olympus-owner@xxxxxxxxxx [mailto:olympus-owner@xxxxxxxxxx] On Behalf
Of Andrew Gullen
Sent: 02 August 2004 03:15
To: olympus@xxxxxxxxxx
Subject: [OM] Re: ( OM ) image sizes, dpi, pixels and pixes etc
on 2004/08/01 9:43 PM, Brian Swale at bj@xxxxxxxxxxxxxxx wrote:
> High Quality JPEG 3000x2000 pixels open file=17mb. Closed file=1.2mb
> Print up to 8x10
>
> Please advise what format the open file is. I doubt it is JPEG.
> Is it TIFF? or BMP? or what ??
>
--snip
I'm almost sure he's saying the file is a JPEG that is 1.2MB on disk, but
when it is opened the decompression expands it (as it's read into memory) to
17 or 18 MB of picture data. Thus the "open file" doesn't really have a type
- it's in whatever internal format the software that opened it uses (perhaps
just an array of pixel values).
--snip
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