ghostscript crashes when embedding fonts in a pdf: caused by png file

I'm using Ubuntu 14.04. I had this problem with a book. I prepared LaTeX source, say book.tex, use pdflatex book to make a book.pdf, and then needed to embed the fonts to send the file to the printer. To do this I usually use the sequence of terminal commands:
pdf2ps book.pdf
(which outputs book.ps) and
ps2pdf -dPDFSETTINGS=/prepress book.ps book-w-embedded-fonts.pdf

But having used this many times without problems, and through several revisions of the text, it crashed one day while executing the last command. The command ps2pdf invokes ghostscript, or gs, with suitable arguments, so this appears as a crash of gs, and the crash dump is placed in /var/crash with a name that tells you it was gs that crashed.

The problem remained after I installed all software upgrades.

To isolate the problem, I used a bisection search on the source, and it turned out that the crash was caused by the inclusion of a png-format graphic file, using \includegraphics from the LaTeX package graphicx. (This was tedious to locate, because there was no problem with pdflatex, I had no idea of the nature of the problem, and for each step of the binary search I had to re-run the font-embedding commands, which take minutes.)

I'm not sure what the problem was with the png file, but I just used gimp to make an equivalent jpg file, and used that instead, and that got me past the problem. The crazy thing about this is that there are other png files included in the source, and they were similarly generated (using Sage) and, even stranger, the same file worked in an earlier draft. It seems unlikely that it was corrupted, since I was able to load it into gimp and make the jpg from it.

The main reason for this post is to flag that it might be useful to check any png-format files, if you ever encounter the same problem.

It would be more satisfactory if I could understand the problem, rather than just walking around and past it. It appears that ps2pdf with this flag is not just adding font data to the pdf file, but is also doing something with the embedded graphics. Can anyone answer these questions:
1. Does pdflatex put a full native pdf description of the included graphics into the output book.pdf, or does it rely on an external graphics engine to render graphics?
2. Same question for pdflatex followed by pdf2ps: what is in the postscript file, in relation to the included graphics? I notice that book.ps is about 5 times larger than book.pdf.

Remote execution needing root access

Using a program on a remote system that needs root privileges and transferring the output to the local system.

The problem:
My scanner is attached to an old computer, let's call it remote-host.  The installed program that runs it needs root privileges, and outputs a PNM image.  (It needs to be run with sudo because the manufacturer did not supply a Linux driver that handled the scanner, and some kind member of the Ubuntu community wrote one and cut some corners.)
I want a single command that I can run on another computer, say local-host, that will scan whatever is on the scanner plate, and save the result as a JPEG in a specified file.

This solution worked:

I made a bash script, scanto, taking one argument
--- the path to the ultimate JPEG file, without
the .jpg extension, and I put it in my path.
Thus, for instance, the terminal command:
scanto fan
saves the scanned image in the file fan.jpg

Here are the contents of the script:

******************************************

#!/bin/bash

# file scanto

# AOF 25-8-2017

[ $# -eq 0 ] \

        && echo Needs an argument  \

        && echo -- an output filename, without extension \

        && exit

echo WARNING:

echo Existing files $1.pnm and $1.jpg will be overwritten!

echo Type ctrl-C next if you don't want that to happen.

echo Preparing to scan on remote-host

echo You will be asked for your privileged password

echo '#!/bin/bash' > scan.sh

echo 'sudo scanimage > ./scratch/scans/temp.pnm' >> scan.sh

ssh myname@remote-host 'bash -s' < scan.sh

echo page scanned to file scratch/scans/temp.pnm on remote-host

echo Preparing to transfer the file from remote-host

echo You will be asked again for your privileged password

scp myname@remote-host:scratch/scans/temp.pnm $1.pnm

echo scanned page copied to $1.pnm

echo Making a JPEG version:

convert $1.pnm $1.jpg

echo JPEG version now in $1.jpg

********************************

The only essential lines are:

echo '#!/bin/bash' > scan.sh

echo 'sudo scanimage > ./scratch/scans/temp.pnm' >> scan.sh

ssh myname@remote-host 'bash -s' < scan.sh

scp myname@remote-host:scratch/scans/temp.pnm $1.pnm

convert $1.pnm $1.jpg

The first two lines create a shell script, scan.sh

The third line uses ssh (secure shell) to execute scan.sh on the remote system, with root privileges.

The fourth line uses scp (secure copy) to copy temp.pnm to the local system.

The last line uses the convert utility to make a JPEG version.

The script also leaves a PNM version on the local system. This is the raw scan, and is useful if I want to use gimp to modify the image.  Add a line with rm $1.pnm  to the script if you don't want this file.  The script also leaves behind a copy of the scan on the remote host, but that file is overwritten each time scanto is called.

I have to be a sudoer on the remote-host, and I have to give my password twice, as the script executes.  I could not see a secure way to give it just once.

                                                           

Printing from Windows and Android on a "classic printer" attached to USB on Ubuntu

I use a ten-year-old computer running Ubuntu 14.04 as a print server for the house, and it does a little bit of file-serving as well.  I don't want to burden it with any other heavy applications, because it can't take it.

It serves the printer using CUPS.

I gave it a static IP address (192.168.1.x) on the domestic network and then I could easily install it as the default printer for all the Linux and Windows machines we have.

The Android devices (phones and tablets) were more of a problem.  Google Cloud Print would work, but required me to run Chrome on the server, and Chrome is heavy. The solution I settled on was to use the app Let's Print Droid. This finds the CUPS server easily and sets itself up.  I can then 'share' in any app that allows that, and select Let's Print Droid.

Using an external package with the Java Development Kit

External packages can be accessed once the compiler can find them.  They usually come in a .jar file. There is lots of advice online about how to tell javac to find them.  The three usual ways are to (1) reset the CLASSPATH environmental variable, (2) use the command-line parameter  -cp, or (3) put the .jar file in some ~\jre\lib\ext directory.

The method least likely to have later unwanted side-effects is (2).  To keep it simple, I put a customised version of javac and java in the working directory where I have the source of
my java program.

Here's an example:   The package JGraphT has classes and methods that do all the standard tasks that you might want on a graph. I wanted to use the Bron-Krombosch algorithm to find a maximum independent set of nodes. I found the package at www.jgrapht.org, downloaded it and put it in my directory $HOME/programs/java.  The .jar file I needed was then:

$HOME/programs/java/jgrapht-1.0.1/lib/jgrapht-core-1.0.1.jar

I made executable shell scripts myjavac and myjava, with the following content:

myjavac:

#!/bin/sh
# file myjavac
# Uses java with classpath to include jgrapht package(s)
javac -cp $HOME/programs/java/jgrapht-1.0.1/lib/jgrapht-core-1.0.1.jar \
$1

myjava:

#!/bin/sh

# file myjava

# runs a java class with a main, adding jgrapht package(s)

# and the current directory

# to the classpath

java -cp $HOME/programs/java/jgrapht-1.0.1/lib/jgrapht-core-1.0.1.jar:. \

$1

Notice the :. that adds the current directory to CLASSPATH, as well as the directory that has the JGraphT package.  I put the following lines into my java source:

import org.jgrapht.*;

import org.jgrapht.graph.*;

import org.jgrapht.alg.*;

Then I just went ahead as usual, using 

myjavac <ClassName>.java 

to compile and 

myjava <ClassName>

to execute, where <ClassName> stands for the name of my source file, instead of javac and java. If you needed to use any other command-line parameters with javac, you would have to make the obvious modifications.  

Replacing quarter-glass on a Toyota

The quarter-glass is the little side window at the back. People break them to get in, and they have to be replaced.  We had to put one in today, and I looked on YouTube.  This guy demonstrated how to do it, and he practically dismantled the whole door, so I thought this post might be helpful.

The main thing is that you have to move the pillar separating the main rear window from the quarter-glass, in order to get the new glass (in its rubber seals) in. You don't have to take the pillar out, just move it enough at the top end.
Roll down the main rear window all the way. Pull the rubber seals off near the pillar. The pillar is attached to the door-frame at the top by one or two phillips-head screws. These might be under or over the frame.  There were two screws underneath in that YouTube video. On our car, there was just one screw, on top. One the screw was out, we could move the pillar enough to get the job done, without breaking anything.
Take your time. Make sure all the seals are fitted back properly, that the main window closes easily, and that the screw fits back in.
I suppose that on some models the pillar may not move enough, and then you are going to have to take down the whole main window, like our friend on YouTube.  Just judge for yourself how far the pillar will move when freed at the top, without the use of excessive force.  If you break it, don't blame me.

Toggle full-screen

F11 toggles between full-screen mode and normal mode.  Use it to get back those bars and tabs at the top of your screen, if they've gone away.

DOS and UNIX line breaks

Here are my scripts 2unix and 2dos, which convert a given text file to one with guaranteed UNIX line breaks or guaranteed DOS line breaks:


#!/bin/sh
# script 2unix
# AOF 14-6-2-05
# make $1 have LF line breaks
# remove all CR:
sed -i 's/\r//' $1
echo $1 now has only LF \(UNIX\) line breaks.
echo \(To view them use cat -e $1.\)



#!/bin/sh
# script 2dos
#AOF 14-6-2-15
# make $1 have CRLF line breaks
# first remove all CR:
sed -i 's/\r//' $1
# then add CR before each LF:
sed -i 's/$/\r/' $1
echo $1 now has only CRLF \(DOS\) line breaks.
echo To view them use cat -e $1.

LaTeX: Putting answers to selected exercises in an appendix to a book

The LaTeX package answers is designed to deal with this.  Most of the online help relates to using it with an article documentclass.    I used it like this, in a book using the memoir documentclass (which allows both A5 (option a5paper) and US Trade (option ebook) paper sizes.  The bit that caused trouble, and which is handled here, is to make sure that the solution is fully and correctly labelled with the coordinates of the exercise, including the subsection number and the sequence number in the subsection, taking account of the fact that only certain numbers in the sequence have solutions.

In preamble:

\usepackage{answers}
%Exercise:
\newtheorem{Exc}{Exercise}[subsection]
%exercise without answer:
\newenvironment{ex}{\begin{Exc}\normalfont}{\end{Exc}}
%exercise with answer in appendix:
\newenvironment{exw}{\begin{Exc}%
\Writetofile{answers}{\textbf{\thesubsection.\arabic{Exc}}}%
$\dagger$\normalfont}{\end{Exc}}
\Newassociation{sol}{Solution}{answers}
\renewcommand{\Solutionlabel}[1]{\null}% suppresses the label

At the start of the document:

\begin{document}
\Opensolutionfile{answers}[exanswers]


In the text:

1. An exercise without a solution:

\begin{ex} Show that
$f(A_1\cup A_2)= f(A_1)\cup f(A_2)$.
\end{ex}

  -- This will set the exercise with a label like

1.2.3.1 Exercise Show that ...

where 1.2.3 is the subsection number, and this is the first exercise in that subsection. The "1.2.3.1 Exercise" will be in bold, and the rest in the ambient normalfont of the document.

2. An exercise with a solution:

\begin{exw} Write out the proofs of all the
remaining identities in the Proposition.
\end{exw}
\begin{sol}
Hint: Imitate the proof given for the first one.
\end{sol}

 -- This will set the exercise with a label like

1.2.3.2 Exercise $dagger$ Write out ...

where 1.2.3 is the subsection number and this is the second exercise in it.  $dagger$ will print as a dagger, flagging the fact that there is a solution given later.  The 1.2.3.2 and the material in the sol environment will be enclosed in a Solution environment and written out to the file exanswers.tex.

Finally, at the point where answers are to appear in the appendix:

\Closesolutionfile{answers}
\input{exanswers.tex}

Multicolumn document in LaTeX

I wanted to make a flier for a book I'd published, and found a quick solution here:

http://timmurphy.org/

This great site has tons of technical solutions.

Converting M/S Word to LaTeX source. Hex codes

I know there is some tool out there that does this, but if  it's just a matter of fixing a few
characters that seem to vanish when you export the word doc to plain text,
then it's useful to know that the unicode hex for

... (ellipsis) is 2026
long dash is 2013
hyphen is 2d
left double quote is 201C
right double quote is 201D
left single quote is 2018
right single quote is 2019

To find the code for a character (visible or not) in a file
open with vi, move the curso to it and type ga

Examples:

To convert all double left quotes to the LaTeX equivalent in vi:
:1,$s/\%u201C/\\lq\\lq/g


e with an acute accent is unicode hex 00e9, so to convert them all to LaTeX:
:1,$s/\%u00e9/\\'e/

Mixing greek and latin text in LaTeX Ubuntu

Don't use the math mode $\alpha$, etc for ordinary greek words.

$ sudo apt-get install texlive-lang-greek

Add to preamble:
/usepackage[greek, english]{babel}
% makes latin/english the default

In the document, switch in and out of greek with
\greektext .... \latintext ...

This allows you to type greek on your keyboard.

An alternative is the switch with
\begin{greek} .... \end{greek}
I haven't used this. It's possibly better for extended greek text.
I've just been interested in putting in occasional words and
short phrases.

Example:

These grounds are quite sufficient for deeming
mathematical training an indispensible basis of real
scientific education, and regarding, with Plato,
one who is \greektext `agewm'etrhtoc%
\footnote{\latintext -- {\it ageometretos }, i.e. ignorant of geometry
(or, perhaps, unskilled in geometry, or indifferent to geometry).
The motto said to have been
carved above the entrance to Plato's
Academy was: \greektext O`udeic `agewm'etrhtoc e`is'itw --
\latintext {\it Let no-one
ignorant of geometry enter.}}
\latintext as wanting in one of the
most essential qualifications for the successful cultivation
of the highest branches of philosophy.
}

How to use Sumatra pdf reader on Ubuntu

Download the windows executable SumatraPDF.exe
and (install and) use wine.

To use it by default, make a script, say sumatra, that does
wine SumatraPDF.exe $1
and make it the default by picking any pdf, right-click -> properties -> open with
and selecting sumatra.

(I found Adobe heavy with Ubuntu Linux 14.04 on an old computer, and inclined
to freeze or crash. Sumatra is much leaner and faster, and works fine.)

Embedding fonts in a pdf made with pdflatex, linux

$ pdf2ps file.pdf
$ ps2pdf -dPDFSETTINGS=/prepress file.ps file-w-embedded-fonts.pdf

(If you don't do this, then the software reading the pdf may make
font substitutions.  This matters if it is proprietary software used by
some printer, for instance.)

Canon MF3010 scanner on Linux Ubuntu 14.04

The MF3010 printer/scanner would print but not scan on Ubuntu, when I first got it. This has now been sorted out, at least to the extent that I can scan.  I'd like to acknowledge the help of the Ubuntu Forum. It has this nice feature that you can sign up to receive an email whenever there is a new post on a specific topic.

Step 1: I first followed these instructions to
download and build sane-backend from source:

In a new subdirectory $HOME/MF3010/sane-backends:

$ sudo apt-get install libusb-dev
$ git clone git://git.debian.org/sane/sane-backends.git
$ cd sane-backends/
$ ./configure --prefix=/usr --sysconfdir=/etc --localstatedir=/var
$ make

(For more detail see:

 http://jonathan.bergknoff.com/journal/scanning-ubuntu-canon-mf3010

The instructions at the end of that piece,
involving moving stuff in the system, are deprecated in the
forum, and anyway can't be used as they stand with Ubuntu 14.04.

Note that libusb is an absolute prerequisite for
any kind of sane functionality.

The make step takes a long time, with many warnings, but
works, as far as I can see.)

Step 2: Second, I uninstalled the version of libsane that came
with Ubuntu14.04.  This automatically removed xsane and
simple-scan as well.  I used the package manager with the GUI,
Ubuntu Software Center.

Third, in directory $HOME/MF3010.sane-backends:

Step 3:
$ sudo make install

With that done,
$ scanimage -V
gives:
scanimage (sane-backends) 1.0.25git; backend version 1.0.25

(Note: you have to have a match of versions here. If you get

scanimage (sane-backends) 1.0.25git; backend version 1.0.23

it means that the old libsane was not removed, or has crept back in.
It will creep back in if you try to reinstall simple-scan
with the package manager, and you'll have to go back to step 2.
)

$ scanimage -L
gives
device `pixma:04A92759' is a CANON Canon i-SENSYS MF3010 multi-function peripheral

You are now good to go.
$ scanimage -h
gives help.

$ sudo scanimage >filename.pnm
gives scary warnings, and I hope I haven't just installed
a trojan, but it
scans whatever is on the scanner plate and saves it as a pnm,
which you can manipulate using gimp (for instance)
into any format you like.

Moving contacts from Blackberry

Blackberry phones allow you to copy contacts from SIM to phone, but when you want to go the other way you have to copy them one at a time. (This was fixed in recent BB's, BB10).  So how do you quickly get your contacts from an old BB to Android?

Solution: Use bluetooth.

I guess this might also work for other phone systems as well.

Purpose of this blog: solutions to technical problems

Here I blog notes on technical issues resolved.
By technical, I mean anything to do with ICT, desktop publishing, all software, machinery.
Mainly, I'll post short notes on things that gave me trouble and are now dealt with.
I'll leave all posts open for comment, so that others can add to or correct what I write.