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Identifying the image type within a PDF file?

 
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patrick j

External


Since: Aug 13, 2006
Posts: 118



(Msg. 61) Posted: Thu Sep 07, 2006 5:13 pm
Post subject: Re: Identifying the image type within a PDF file? [Login to view extended thread Info.]
Archived from groups: comp>sys>mac>apps, others (more info?)

On Thu, 7 Sep 2006 03:39:26 +0100, dorayme wrote
(in article
):

> I know the Gang is out to get me. That is as plain as day.

Yes it is :)

I've edited the quote slightly because I don't know who leads this
group. Sometimes the most vocal person is not the leader.

If people don't want to read dorayme's posts then why don't they just
kill file him?

I hardly ever read dorayme's posts, but those that I do read seem
pretty harmless.

I think he's often off topic but he doesn't seem to be rude or
ill-mannered in nature.

There is a group of people on this forum who are very ill-mannered in
nature and that is a much greater problem than the benign albeit
sometimes banal postings of dorayme.

If you look through this thread you can see that dorayme's initial
posting is absolutely fine for participation in this newsgroup, it is
on topic and certainly not rude. There then follows a series of
postings from this group of people which are rude and ironically off
topic despite their apparent self-righteous claims to be the upkeepers
of all that is right in usenet - those ones are always the worst :)

Personally I think dorayme would do well to just kill file the people
in this group now and waste no more time with them.

Equally those people who don't like dorayme's postings should just kill
file him.

As a general statement:

When you are responding to a post on usenet you are communicating with
a fellow human being, someone who deserves respect.

There are guidlines for usenet but you are not the enforcer of them and
if they are being broken then just politely pointing this out with good
humour usually sorts it out.

The culture of rudeness towards people on these comp.sys.mac newsgroups
will not benefit anyone. It will not benefit the immediate victims nor
will it benefit the perpetrators. When people are being rude and
bullying in nature it is because they themselves are unhappy.

Think about it this way, happy contented people don't go around
starting arguments over nothing; do they?

Start trying to be happy and contented. Stop starting arguments over
nothing.

I won't be responding again in this thread.



--
Patrick
Brighton, UK

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Sue Rodgers

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Since: Sep 30, 2003
Posts: 98



(Msg. 62) Posted: Thu Sep 07, 2006 5:13 pm
Post subject: Re: Identifying the image type within a PDF file? [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)

patrick j wrote:

> I've edited the quote slightly because I don't know who leads this
> group. Sometimes the most vocal person is not the leader.

The point is that there's no gang, no leader, just individuals posting
according to their own wishes, and they sometimes happen to agree.
Everyone will have their own opinion of another and his/her posts.

I happen to believe that dorayme is likely a nice person but one who has
a way of irritating people and simply cannot accept the possibility that
this is the case. Bear in mind that, one called a narcissist, she went
on at length about herself.
--
Living is easy with eyes closed, misunderstanding all you see...

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dorayme

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Since: Feb 21, 2006
Posts: 787



(Msg. 63) Posted: Fri Sep 08, 2006 8:17 am
Post subject: Re: Identifying the image type within a PDF file? [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)

In article
,
patrick j wrote:

> As a general statement:
>
> When you are responding to a post on usenet you are communicating with
> a fellow human being, someone who deserves respect.

I think this sums things up nicely, Patrick. True, I am not
actually human... but hell, I have feelings. And sort of like to
make friends with you lot online. I just react a bit I guess
when... better stop (Sue is a voice telling me this, embedded in
my martian conscience circuitry)

--
dorayme
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glen herrmannsfeld

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Since: Jun 02, 2004
Posts: 4



(Msg. 64) Posted: Sun Oct 15, 2006 6:05 pm
Post subject: Re: Identifying the image type within a PDF file? [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)

AES wrote:

> Is there any quick and easy way to determine the basic or current
> structure of an image of unknown original vintage that is embedded in a
> PDF file, without trying to extract the image, or edit the whole PDF? --
> for example, by searching for specific strings inside the PDF file with
> a text editor, or by examining some metadata associated with the file
> using Acrobat?

I am not sure what you mean by unknown original vintage. There are
a variety of ways to store data inside a PDF file, and the way to
decode that data is indicated in the file. The structure isn't
too complicated to follow.

If you want a deeper answer, you will have to explain more.

-- glen
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AES

External


Since: May 31, 2004
Posts: 361



(Msg. 65) Posted: Sun Oct 15, 2006 8:26 pm
Post subject: Re: Identifying the image type within a PDF file? [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)

> AES wrote:
>
> > Is there any quick and easy way to determine the basic or current
> > structure of an image of unknown original vintage that is embedded in a
> > PDF file, without trying to extract the image, or edit the whole PDF? --
> > for example, by searching for specific strings inside the PDF file with
> > a text editor, or by examining some metadata associated with the file
> > using Acrobat?
>
> and glen herrmannsfeldt replied
>
> I am not sure what you mean by unknown original vintage. There are
> a variety of ways to store data inside a PDF file, and the way to
> decode that data is indicated in the file. The structure isn't
> too complicated to follow.

By "unknown vintage" I just mean a situation where I have no idea who
originally created some PDF file that's open on the screen in front of
me, or how they created it, but I'd like to extract some of the image
content of the page that's before me.

As for image formats, what I know is that as a practical matter when I
create a PDF page myself, I can drag or embed multiple images or files
from my HD into that page, some of these files being JPEG raster images,
some of them being EPS or Illustrator vector images (and other formats
also, but those are the ones I use). I also know these images retain
some if not all of their original character in the PDF file, 'cause I
can extract and recover the raster images as JPEGs using Acrobat, and I
can (and frequently do) open the PDF page in Illustrator and recover (or
edit) the vector images.

My naive assumption had been that PDF must have somehow put an
identifying "wrapper" around each of these images and tucked them away,
more or less unchanged inside its file content -- at least that might
seem the simplest way to handle them. I gather it's somewhat more
complicated.
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dorayme

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Since: Feb 21, 2006
Posts: 787



(Msg. 66) Posted: Mon Oct 16, 2006 1:56 pm
Post subject: Re: Identifying the image type within a PDF file? [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)

In article ,
AES wrote:

> I also know these images retain
> some if not all of their original character in the PDF file, 'cause I
> can extract and recover the raster images as JPEGs using Acrobat, and I
> can (and frequently do) open the PDF page in Illustrator and recover (or
> edit) the vector images.

What is the precise nature of the evidence for this? I mean
details about sizes etc. What is your methodology? If they are
vector then they are expandable without loss mostly, it is no use
putting them in Illustrator and seeing them go smaller and back
to the "native" size. The vectoring test is to see that the
mathematical formulae are operating well at above the size you
used to export to PDF - not sizes below, because below or equal
is consistent with raster.

--
dorayme
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inez

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Since: Aug 07, 2006
Posts: 4



(Msg. 67) Posted: Fri Oct 20, 2006 3:59 am
Post subject: Re: Identifying the image type within a PDF file? [Login to view extended thread Info.]
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rpresser

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Since: May 11, 2006
Posts: 4



(Msg. 68) Posted: Tue Oct 24, 2006 2:34 pm
Post subject: Re: Identifying the image type within a PDF file? [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)

inez wrote:
> On 10/15/06 10:26 PM, AES commented:
>
> > By "unknown vintage" I just mean a situation where I have no idea who
> > originally created some PDF file that's open on the screen in front of
> > me, or how they created it, but I'd like to extract some of the image
> > content of the page that's before me.
>
> I guess my first question would be, do you have permission from the
> copyright owner to extract/use images within the PDF?
>
> I believe that once a raster image is embedded in a PDF it becomes just
> that, a raster image, and if there is a format it's probably Photoshop or
> PDF.

There are a variety of ways for raster images to be embedded in a PDF,
of which some of the most important attributes are different color
spaces and different compression methods. The decision of what to use
depends on the PDF generator, although you can count on a few things:
lossy JPEG compression stays JPEG compression, lossless rasters stay
lossless rasters, and colors usually stay in something like the
original colorspace.

The image "format" - meaning, in this case, exactly how the pixels are
coded into bytes - is specific to the PDF file format; it is not in any
way a simple "wrapper" around the original TIFF/PNG/JPEG/etc. byte
stream. When you extract an image from a PDF, you always have a choice
of what file format to save it in -- the original identity of the
image's file format before you placed it in Quark or whatever is
totally lost.

> Also, you aren't getting the original raster image. If I import a TIFF image
> into Quark, scale it down and make the picture box smaller than the image to
> crop out parts, then once it's made into a PDF it adapts that rescaling as
> the actual size, raising the resolution, and the picture box has become a
> clipping mask. If in Acrobat you right click a raster and select Edit it
> will open at its scaled, clipped dimensions and resolution in Photoshop.
> Same if you import PDF image from Photoshop. In Illustrator you can delete
> the clipping and copy/paste the image in PS, but it will retain the
> scale/resolution as output from Quark to PDF.

These types of manipulations are completely dependent on what software
you are using to generate the PDF -- Quark, Photoshop, whatever.

> I'm sure that's completely unclear, convoluted and probably incorrect;)

It wasn't that bad; it is certainly enough to know what things cannot
be done, and what things should be avoided.
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AES

External


Since: May 31, 2004
Posts: 361



(Msg. 69) Posted: Tue Oct 24, 2006 5:48 pm
Post subject: Re: Identifying the image type within a PDF file? [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)

In article ,
"rpresser" wrote:

> The image "format" - meaning, in this case, exactly how the pixels are
> coded into bytes - is specific to the PDF file format; it is not in any
> way a simple "wrapper" around the original TIFF/PNG/JPEG/etc. byte
> stream. . . . . . . . . . . . . . . . . . . . . . . . . . the original identity of the
> image's file format before you placed it [using?] Quark or whatever is
> totally lost.

Having learned this, I can now understand that my original question was
asking for something that's just not meaningful, or just not there, at
least as regards raster images within a PDF file.

So, thanks . . .
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