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

[Ralph Giles]

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