[softwarelist] Re: JPEGs files in PostScript

[Mike Williams <akalat@xxxxxxxxxxx>]

On 20/4/06 5:25 pm, "Gavin Crawford" <gav@xxxxxxxxxxxxxxxxxxxx> wrote:

> In article <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?
> 
> When printing to PostScript with the colour option off, RGB sprites will
> be converted to 8bit greyscale and hence suffer from being chopped into
> many smaller bitmap images (as is usual with the PostScript driver).
> 
> JPEGs on the other hand don't, and will appear in full colour in the
> resulting PostScript output.
> 
> If you find that some of your JPEGs are being converted to greyscale
> images it is because OPro is sending them as sprites to the print
> stream. Most likely, this is because you have some 'image processing'
> applied to the JPEG in OPro, which then has to deal with it as a sprite,
> so will print it as a sprite.
> 
> There is a small problem with OPro in that once image processing has
> been applied to a picture it cannot be removed, even if the Default
> button is clicked. It is the picture fame that retains the processing
> settings, so even if you drop a completely different picture into the
> frame OPro still handles the picture as if it's a sprite.
> 
> The only way to remove the 'processing' effect in the frame is to
> 1. delete the picture from the fame,
> 2. type some text to convert it to a text frame,
> 3. delete the text,
> 4. and drag the picture back into the frame.
> Then OPro will forget the processing state of the frame and JPEGs will
> once again be handled as JPEGs when printed to PostScript.
> 
> If you want the images to be monochrome in the final output, then it's
> best to keep them as JPEGs but first convert them to greyscale images in
> a bitmap editor such as DPScan / PhotoDesk / Photoshop etc.

Thanks - that helps to explain what is happening. I agree it is better to
start with greyscale images but was trying to avoid any further degradation
of images by taking a JPEG, processing, and then resaving as a JPEG, but
JPEG format certainly avoids the problems you get quite often when sending
monochrome sprites to a PostScript file.

Mike Williams

• References:
  • [softwarelist] Re: JPEGs files in PostScript
    • From: Gavin Crawford

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[softwarelist] JPEGs files in PostScript

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[softwarelist] Re: JPEGs files in PostScript