Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > alt.os.linux > #51579

Re: A problem with "convert" - security related

Cross-posted to 2 groups.

Show all headers | View raw

On 12/11/2018 15.21, Paul wrote:
> Carlos E. R. wrote:
>> On 11/11/2018 05.26, Paul wrote:
>>> Paulo da Silva wrote:
>>
>> ...
>>
>>> I agree it doesn't make any sense. Not on writes.
>>> It's a reading/interpreting issue.
>>>
>>> One of the reasons these capabilities existed in the first
>>> place, is some laser printers had "resident" fonts. These
>>> may have been stored on a hard drive inside the laser printer.
>>> At the time, flash (NOR) memory was too expensive to hold
>>> the fonts.
>>>
>>> You could send a specially formulated .ps print job, to send
>>> a font to the printer. I've never done it, but heard you
>>> could do such a thing at the time.
>>>
>>> Some file capabilities existed in PostScript, that might not
>>> have been there, if it wasn't for the printer requirement.
>>>
>>> Today, we send embedded fonts in documents, so a printer
>>> with resident fonts isn't as necessary. The embedded font
>>> is a subset. I have document samples here, where a font table
>>> only has one character in it, as an example of how few characters
>>> they're willing to embed when sending them with the document.
>>
>> All printers, even ribbon printers (pin matrix), have "fonts" :-)
>>
>> In some form. They need to handle fonts in order to be able to print
>> plain ascii.
>>
>> Well, maybe winprinters don't, I do not know.
>>
>> Postscript printers have more sophisticated fonts. They can be scaled
>> (vector based?) and you do not see the "dots", the quality normally
>> keeps. Similarly I think PDF printers also have some fonts, because the
>> PDF format assumes the receiver knows how to handle a small set of
>> fonts. You can try print directly (raw) a PDF without embedded fonts and
>> it should print.
>>
>> My printer handles ps and I can send it plain ps files without sending
>> fonts and they print fine.
>>
> 
> There's a couple ways to print.
> 
> The "clumsy" way, is to send a bitmap or pixmap
> image of what is to be printed. This usually takes
> a bit of bandwidth (but not by todays standards). Back
> in the day, we had some pretty bad LAN standards.

Just use the parallel printer port ;-p


> The first laser we had at work, didn't have an internal
> interpreter. It was a "dumb" printer. It had what
> is known as a "video interface". The card feeding it,
> sent a 2Mbit/sec video signal. The "image" was then
> drawn on the drum as the drum rotated. Print jobs
> sent to such a printer, consisted of bitmaps, and
> the driver on the computer sitting next to the printer,
> would send them out via the video interface.

I have not seen those.

However, on pin and ribbon printers the computer could send text, or
just one band of the image. I don't know but I think the computer
generated the entire image then sent it band by band to the printer. My,
they were slow!  It happened with Windows 3, many "text" print jobs were
done that way. Minutes per page. WordPerfect in MsDOS was much faster
with very good (for the times) results.


> Later printers, used higher level languages, like
> PostScript or PCL or whatever. The printer has
> a parser, to read the more compact representation
> of a print job, and convert to a bitmap. (One of the
> printers had a 25MHz processor, a RISC.) On some
> of those printers, the printer didn't have enough
> RAM to hold the whole sheet of paper. This
> meant that the RAM functioned as a "fraction-of-a-page
> buffer". And the parser had to stay ahead of the
> print rate, to keep the buffer full. Only rich
> companies could afford to put more RAM in the
> printer, so an entire glorious page could be
> held in RAM. Some of those first machines were
> that cheesy.
> 

Oh, I have seen the "out of memory" message on modern laser printers.
Not the huge type, but home/small office.

The last one I saw recovered automatically somehow - maybe the computer
sent the job differently. On mine I have to use another hp language
instead of ps when it errors.

> It's those processor-equipped machines, that
> might have a hard drive with fonts. It was an option.
> It also means you could make very compact print
> jobs. You could tell the interpreter "I'd like to
> use Times Roman please". Then specify a character
> string and have it rendered immediately at the
> current point in space. This is better than having
> to download a 2MB font, which on the old networks,
> took a while. This worked well enough, we used to
> hand-craft PostScript files, while trying examples
> from the Red Book.
> 
> Rosetta has various tasks written in different languages,
> and this is "Hello World" written in PostScript language.
> 
> https://rosettacode.org/wiki/Hello_world/Line_printer#PostScript
> 
> <</PageSize [595 842]>> setpagedevice  % set page size to DIN A4
> /Courier findfont                      % use Courier
> 12 scalefont setfont                   % 12 pt
> 28 802 moveto                          % 1 cm from the top and left edges
> (Hello world) show                     % draw the string
> 
> That example would rely on the printer having
> the Courier font onboard. Modern printing tool
> chains, probably would not take a chance on that,
> and they would send an embedded subset of Courier along
> with the print job.

The driver should know what fonts the printer has. There are a few all
printers should have (I never remember which), the rest are extra.

It has to know at least one font, with variations, or the printer can
not do plain text.

-- 
Cheers,
       Carlos E.R.

Back to alt.os.linux | Previous | Next — Previous in thread | Find similar | Unroll thread

Thread

A problem with "convert" - security related Paulo da Silva <p_s_d_a_s_i_l_v_a_ns@netcabo.pt> - 2018-11-10 02:35 +0000
  Re: A problem with "convert" - security related Paul <nospam@needed.invalid> - 2018-11-10 00:15 -0500
  Re: A problem with "convert" - security related stepore <linshine@here.now> - 2018-11-10 00:34 -0800
    Re: A problem with "convert" - security related Paul <nospam@needed.invalid> - 2018-11-10 07:32 -0500
    Re: A problem with "convert" - security related Paulo da Silva <p_s_d_a_s_i_l_v_a_ns@netcabo.pt> - 2018-11-10 17:19 +0000
      Re: A problem with "convert" - security related Paul <nospam@needed.invalid> - 2018-11-10 17:03 -0500
        Re: A problem with "convert" - security related Paulo da Silva <p_s_d_a_s_i_l_v_a_ns@netcabo.pt> - 2018-11-11 02:45 +0000
          Re: A problem with "convert" - security related Paul <nospam@needed.invalid> - 2018-11-10 23:26 -0500
            Re: A problem with "convert" - security related "Carlos E. R." <robin_listas@es.invalid> - 2018-11-12 14:17 +0100
              Re: A problem with "convert" - security related Paul <nospam@needed.invalid> - 2018-11-12 09:21 -0500
                Re: A problem with "convert" - security related "Carlos E. R." <robin_listas@es.invalid> - 2018-11-12 17:09 +0100

csiph-web