> -----Original Message-----
> From: Peter B. West [mailto:[EMAIL PROTECTED]]
> I have some questions about the handling of colour which I will ask of
> the list generally, although I noticed Tore's recent colour related
> contributions, so he may be the one to enlighten me.
>
> Color (to use the official spelling) is one of those areas of the spec
> whose precise description is deferred to other documents, so I am hoping
> someone on the list has done all of the hard work.
hehe, unfortunately I haven't done all the hard work, but can give you some
pointers.
> In
> .../datatypes/ColorType.java the ColorType is defined as a set of
> floating point numbers: red, green, blue and alpha. From the code, it
> is apparent that the RGB components are in the range 0 to 1.0.
>
> Is this also true of alpha?
yes
> Why this particular representation? Is it mandated in the sRGB
> document, or is it the representation used by PDF?
I don't think it's mandated by sRGB but the representation is used in PDF.
> What is a color profile? In the recently updated (by Tore)
> ColorSpace.java, it is represented as a byte array. What is the
> function of this byte array?
You can find a lot of information about ICC profiles at
http://www.color.org/
The short version is that a color profile is errr, a color profile :)
The point is to make color handling consistent. Let's assume that you have a
calibrated system (you must have a calibrated system if it should be any
point).
Then you scan an image, edit it in photoshop and sends it to a printer. All
those devices (your scanner, screen and printer) probably have different
color profiles and by embedding an icc profile you ensure (well, almost)
that what you see on the screen is the same that comes out of your printer).
The byte array used in ColorSpace.java is the embedded icc profile in the
jpeg and it's sent directly to the pdf. This is just a support for icc
profiles in jpegs (which could easily be extended to other image formats),
but if we should provide full support for the fo:color-profile element a lot
more work needs to be done.
> What is the relationship between the the linear RGB space and sRGB,
> which, from my glance at the document, seems to involve a color profile,
> and between the sRGB and the ICC color profiles?
sRGB (Standard RGB) was defined by HP, Microsoft and Pantone in '97 (unless
my memory fails me...) and is the standard color space from html 3.2 and css
1.0
You can find a lot info about sRGB if you search for e.g. "Standard RGB
sRGB" on google. Among the hits are:
http://www.color.org/sRGB.html
http://www.w3.org/Graphics/Color/sRGB.html
sRGB is a limited color space, there are a lot of colors you can't express
in sRGB. E.g. pastel colors can be described in CMYK but not in RGB.
My knowledge about these things is limited but if you ask someone in the
press industry they can lecture you hours about problems with reproducing
colors (just don't belive everything they say about CMYK - it's not that
great :)
Tore
>
> All information will be gratefully received.
>
> Peter
> --
> Peter B. West [EMAIL PROTECTED] http://powerup.com.au/~pbwest
> "Lord, to whom shall we go?"
>
>
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