Re: compresslevel and png graphics (mkiv)

[luigi scarso <luigi.scarso@gmail.com>]

On Thu, May 26, 2011 at 12:52 PM, Peter Rolf <indiego@gmx.net> wrote:
> Am 25.05.2011 21:54, schrieb Hartmut Henkel:
>> On Wed, 25 May 2011, Hans Hagen wrote:
>>> On 25-5-2011 2:43, Peter Rolf wrote:
>>>>
>>>> I just made a one pager (TEXpage) out of a big png graphic
>>>> (5900x4094). The compressed size of the graphics is normally around
>>>> 1.37MB on the highest png compress level (9) and 1.32MB after using
>>>> optipng (only around 3% reduction this time). To my surprise the
>>>> size of the final PDF was about 2.3MB. After adding
>>>> '\pdfcompresslevel9' the size went down to 1.48MB. Still not what I
>>>> wanted...
>>>>
>>>> So I was wondering: is there an option to embed the png graphic as
>>>> it is (no re-compression)?
>>
>> no. There is a "PNG Copy" function for literal embedding of the PNG
>> file, but that triggers only, if the file simultaneously satisfies quite
>> a few conditions, which are about: non-interlaced, no palette, no
>> transparency, no gamma coming with it, no gamma modification requested,
>> no white adjustment in the PNG, and a few more rare others. Else it's
>> de-compressed and then re-compressed to the \pdfcompresslevel, and
>> additional streams and dicts are added. You see in the log if it finally
>> was "PNG Copy" or not.
>>
> Sigh, most of my graphics use (and need) transparency.
> So the only advantage I get from optipng is the smaller file size on my
> disk. Sad, but good to know. ;-)
>
>> Preprocessing the PNG, e. g., by convert, sometimes changes it that it
>> gets copyable. Obviously flattening transparency also helps.
>>
>> Anyway direct embedding or not can have positive or negative influence
>> on the PDF file size. E. g. if a PNG is copied verbatim, and it contains
>> lots of meta-data info, the PDF file will probably get larger, since
>> normal PNG embedding removes all these info chunks.
>>
> And what about icc profiles?
removed, I suppose.
Not really a big problem, and doable in mkiv
(see
Hacked image color space.
in
texmf-dist/doc/pdftex/manual/samplepdf
of a recent texlive)



-- 
luigi
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