[gs-devel] Getting a JPX stream's colorspace

[Igor V. Melichev]

Ralph,

> It's possible then that we could do other hacks, like editing the page
> dictionary and restarting the page if we resolve a JPX stream with
> opacity information.

It would cause changes to device interface and to many devices.
Currently the device interface doesn't define an erasepage method.

> What does GhostXPS currently do for transparency detection?

This question to be addressed to Tor.

Igor.

----- Original Message ----- 
From: "Ralph Giles" <ralph.giles at artifex.com>
To: "Igor V. Melichev" <igor.melichev at artifex.com>; 
<tor.andersson at artifex.com>
Cc: <gs-devel at ghostscript.com>; <alex.cherepanov at Artifex.com>
Sent: Wednesday, January 09, 2008 10:40 PM
Subject: Re: [gs-devel] Getting a JPX stream's colorspace


> On Sat, Dec 01, 2007 at 05:27:16PM +0300, Igor V. Melichev wrote:
>
>> Not exactly. We can decode the image and send as an RGBA stream
>> (or CMYKA, or the like), then the stream goes to a T-like pipe,
>> which selects RGB (or CMYK) and A into separate streams.
>> The T pipe looks as a writing filter.
>> I've did such thing - search for "compression_chooser"
>> in gs/src.
>
> Ok, I see what you mean.
>
>> Nevertheless if a page contains a transparent JPX image,
>> we can't know about it from the page dict.
>> So we'll need to install it later - after the rendering is started,
>> and it's a kind of unusual. Possibly it will need some improvement here.
>
> I don't believe I've seen a JPX image stream with transparency in PDF,
> and the PDF Reference leaves the composition details explicitly
> unspecified, but I'm sure someone will eventually do it.
>
> It's possible then that we could do other hacks, like editing the page
> dictionary and restarting the page if we resolve a JPX stream with
> opacity information. However, XPS (and SVG) with an explicit RGBA
> rendering model will have a tougher time with this.
>
> What does GhostXPS currently do for transparency detection?
>
> -r
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