Re: Rendering differences between PDF viewers

[Peter Rolf <indiego@gmx.net>]

Am 18.04.2012 09:38, schrieb Hans Hagen:
> On 18-4-2012 02:49, Kip Warner wrote:
>> On Tue, 2012-04-17 at 12:48 +0200, Peter Rolf wrote:
>>> Hi Kip,
>>>
>>> give it a try and add this to you document...
>>>
>>>
>>> \startluacode
>>>
>>> backends                = backends                or { }
>>> backends.codeinjections = backends.codeinjections or { }
>>>
>>> function backends.codeinjections.rgbtransparencygroup()
>>>      local d = lpdf.dictionary {
>>>          S  = lpdf.constant("Transparency"),
>>>          CS = lpdf.constant("DeviceRGB"),
>>>          I  = true }
>>>      lpdf.registerpagefinalizer(function()
>>> lpdf.addtopageattributes("Group",d) end)
>>> end
>>>
>>> backends.codeinjections.rgbtransparencygroup()
>>>
>>> \stopluacode
>>>
>>>
>>> This does not work, if you also use CMYK based graphics/pictures in your
>>> document (as this is done document wide).
>>
>> You know Peter, I must admit. ConTeXt has made me rather cynical at
>> times. I don't know how many times I've tried a snippet of this or that,
>> only to have it do exactly what I hadn't intended. Having said that,
>> every now and then I am blown away when something I never expected to
>> actually get working, gets working. Thank you so much, that worked
>> beautifully. Both Evince (poppler based) and AR look identical now.
>>
>> I stuck it in my environment file. I wonder if there is a safer way of
>> doing this than via "inline asm", so to speak. Also, maybe for my
>> benefit, and anybody else having the same problem, you might be able to
>> explain what was happening?
> 
> At some point it can become an option (or semi automatic) but the
> problem is that we don't know in advance if we operate in rgb or cmyk. I
> can imagine that when we have enabled cmyk and disabled rgb or reverse,
> it can be added automatically but even then users must make sure that
> all images are in the right colorspace as well. And what with spotcolors?
> 
> Hans
> 
I understand that there is no easy or general solution for this.
But on the other hand is PNG currently the only way to use transparent
bitmaps in TeX. The usage of transparent PNG is quite common, so this is
a general problem that should be solved.

I like your idea of automatically adding such groups, if the user
declares the color space beforehand. Also no answer for the spot color
problem, but as long as the user does not limit the used color spaces,
things can stay as they are. Just my 2 cents.

Peter
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