[softwarelist] Re: JPEGs files in PostScript

[Martin Wuerthner <public@xxxxxxxxxxxxxxx>]

In message <C06D5790.1984C%akalat@xxxxxxxxxxx>
          Mike Williams <akalat@xxxxxxxxxxx> wrote:

> If I have an Ovation Pro document with colour JPEGs embedded. I am then
> outputting to PostScript (PostScript 2 driver) with the colour option not
> enabled. The PostScript file is then distilled on a Mac and viewed in
> Acrobat. I would expect, with sprites for example, for all colour images to
> appear in monochrome, but in a recent example with embedded colour (RGB)
> JPEG images some appear to have been converted to monochrome, while some
> remained in colour.
> 
> Can anyone tell me what happens to embedded colour JPEG images when
> outputting what should be a monochrome PostScript file?

Switching off the "Colour" option in the PostScript driver does not 
guarantee a monochrome PostScript file. It just allows the driver to 
convert colour information to monochrome for whichever graphical 
elements it sees fit. The reaons behind this is that any monochrome 
PostScript printer will happily accept colour PostScript and do its 
own monochrome conversion. The main reason for having the "Colour" 
option in the first place is that converting colour information to 
greyscales usually leads to more compact output.

So, if you want a monochrome PDF file, you need to do the conversion 
to monochrome in the source application.

If you want good results and if you have any bitmaps in the document, 
then you are advised to never switch the "Colour" option off in the PS 
driver, even when producing monochrome output. Use 16M colour sprites 
of greyscale JPEGs and avoid sprites with 256 colours or less - at 
least until there is a better PostScript driver...

Martin
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Martin Wuerthner          MW Software          martin@xxxxxxxxxxxxxxx
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• References:
  • [softwarelist] JPEGs files in PostScript
    • From: Mike Williams

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[softwarelist] Re: JPEGs files in PostScript