[softwarelist] Importing EPSs with TIFF preview (Ovation Pro for RISC OS)

I've been following the thread about PDF and EPS import into
Ovation Pro for Windows. This is a different, but related
problem.

I use EPS images a lot with Ovation Pro for RISC OS (v2.77
20/1/07), as a way of importing PDFs and, in the absence (so far)
of a composite-CMYK-aware printing system, of including CMYK
vector files and greyscale images in documents. Long ago I
decided that GhostScript was not up to the job of converting
PostScript or PDF to EPS -- apart from anything else, it had an
annoying habit of rasterising Type 3 fonts as far as I remember.
So for some time I have used Acrobat Distiller on a Mac to
convert the output of the RISC OS PostScript driver to PDF, and
Adobe Acrobat to convert these PDFs, or those received from other
people or exported from Artworks, to EPS. By including a TIFF
preview these can of course be viewed as 8bpp proxy images in
Ovation Pro. For bitmap images only, Adobe PhotoShop will export
EPSs, again with a TIFF preview.

Having just upgraded from Acrobat Professional 7.0.8 to 8.0.0,
Ovation Pro no longer displays the TIFF previews from the EPSs
exported by Acrobat. I have reported this as a bug to Adobe, but
don't hold out much hope of them doing anything about it, so
unless Ovation Pro can accommodate a wider rang of EPSs I will
have to continue using Acrobat 7 for EPS conversion.

The TIFF preview follows %%EOF[return] in the EPS file and
consists of two bytes, either "MM" (indicating big-endian) or
"II" (indicating little-endian), followed by the two-byte number
&002A, followed by a 4-byte offset, etc., all big- or
little-endian depending on what is specified by the first two
bytes. I've put some files on my web space to compare:

http://www.newble.com/DOCP.pdf (the PDF file from which the
following two were created) -- 10K

http://www.newble.com/DOCP_7.eps (DOCP.pdf saved as PostScript 3
EPS with TIFF preview using Acrobat Professional 7.0.8) -- 150K

http://www.newble.com/DOCP_8.eps (DOCP.pdf saved as PostScript 3
EPS with TIFF preview using Acrobat Professional 8.0.0) -- 266K

http://www.newble.com/TIFF_6_specification.ps (TIFF 6.0
specification -- see p.13 onwards) -- 1046K

Both DOCP_7.eps (at address &1004B) and DOCP_8.eps (at address
&2D1A1) have the "MM" header, indicating big-endian numbers, yet
everything following (as far as I have followed the file
structure through) seems to be big-endian in DOCP_7.eps but
little-endian in DOCP_8.eps.

I have tried changing "MM" to "II" in DOCP_8.eps but Ovation Pro
still does not display the preview. I'm not altogether surprised,
because I seem to remember a long time ago using a
little-endian-preview EPS received from someone else, which /did/
have the correct "II" header, but whose preview would not
display. In other words, Ovation Pro does not seem to support
little-endian TIFF previews.

So the questions are:

i) How difficult would it be to extend the EPS TIFF preview
decoder in Ovation Pro for RISC OS to handle both big-endian and
little-endian previews?

ii) If that were possible, could it also make an intelligent
decision as to the actual byte order, rather than assuming what
the two header bytes tell it? In other words, if the two bytes
following "MM" or "II" are &2A &00 assume the rest of the file is
little-endian, and if they are &00 &2A assume it is big-endian,
ignoring the "MM"/"II".

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