PC Plus HelpDesk - issue 245
|This month, Paul Grosse gives you more insight into
some of the topics dealt with in HelpDesk
From the pages of HelpDesk, we look at:
- Preserving Permissions on USB Flash Drives;
- Light-weight Paper;
- Sendmail in programs - Sending mail from
- Sub-Pixel Hinting a.k.a. Cleartype(tm);
- How Sub-Pixel Hinting Works;
- Adding/Removing Sub-Pixel Hinting - Windows;
- Adding/Removing Sub-Pixel Hinting -
Preserving Permissions on USB Flash
If you run
a Linux/UNIX-like operating system, you will no doubt
like the file-level security that exists. If you save
files on a USB Flash Drive, then you will probably want
to make it more difficult for you to change by accident
certain files that are on a USB Flash Drive and this is
where UNIX-like file system permissions come in to play.
Taking into account that the files can always be
copied, if you want to make it effectively impossible for
people to read files that are on there, you should also
use some form of encryption.
By default, these drives come formatted with one of
the FAT file systems. This means that they can be read
and written to on virtually any Personal Computer,
whether it is a PC running Windows, a PC running any of
the flavours of Linux/BSD/UNIX or even a Mac. However,
there are several subtle disadvantages:
- FAT doesn't know what permissions are so you can
find that some users have ownership rights
assigned to them as in the screenshot above-right
('gecko' owns the files but under the FAT
partitions, 'paul' has become the owner because
'paul' is the current user - just unplugging the
drive, opening up another account and reinserting
the drive is guaranteed to change things like
this and you might find that you don't even have
to take out the drive to achieve this on some
- FAT doesn't know which files are executable so,
you could end up with a program that you don't
want to run being run, because all files under
FAT are marked as executable by the system
(Windows goes on the file extension which is
completely insane); and,
- With FAT, there are only 26 letters of the
alphabet. Therefore, if you have two files: one
called 'Index.html' and the other called
'index.html', the later one that is written to
the directory will overwrite the former one
(theoretically, there are 512 possible index.html
file names with capitalisation in all of the
variations such as 'index.html', 'inDEX.hTMl' or
'InDex.HTMl' which FAT sees only as one file
So, how do we get around these inflexibilities? The
answer is that we can format the USB Flash Drive with a
UNIX-like file system such as ReiserFS (this also has the
advantage that it is a proper journalling file system).
|Open up Control Center and select 'YaST2
modules'/ 'System'/ 'Partitioner'.
|On the right, you will see a warning appear.
Click on 'Yes'.
|This is the drive and partition display -
Our USB Flash Drive - being a serial
device - is in '/dev/sdc' and has a FAT32 partition in
We need to get rid of this, replacing it - for the
purposes of this tutorial - with a Fat32 partition and a
So, make sure that the existing Fat32 partition is
highlighted and then click on 'Delete'.
|Don't worry about making a mistake with the
previous step because you are protected by a query box.
you are sure that you have selected the correct
partition, click on 'Yes'.
|Now, it looks like this with only the disk
listed - in this case, '/dev/sdc'.
Next, we have to put
some partitions on it.
|Click on 'Create' and the dialogue box
on the right appears. This allows you to select the drive
that you want to create a partition on.
|MAKE SURE YOU
SELECT THE CORRECT ONE.
In this case,
it is '/dev/sdc'.
|Next, you will be asked what type of
partition you want to create (so, even if you did select
the wrong one in the last dialogue box, you can still
|We'll select 'Primary' - you are allowed four
|This is the dialogue box that we'll use to
create our partition.
In the 'Format' frame, we need to
select our file system - as there are no file systems on
the partition yet, the 'Format' radio button is
|Click on the drop-down combo - it is already
set to 'Reiser' which is the default.
Select 'FAT' from
the list - you can see that there are a number of file
systems that you can choose from: some journalling and
|If you click on 'Options', you get the
dialogue box on the right. It allows you to specify the
number of FATs in the file system, the size of the FATs
(12-, 16- or 32-bit) and the number of root directory
entries. These are all set to reasonable defaults by the
system, according to the size of the partition you want
to specify so there is no real need to specify them here.
|Next, we need to specify the number of
cylinders that this partition will have. There are 1015
cylinders on this drive (0-1014) so, as we want to make
two, roughly equal partitions, I have typed 507 for the
|Following that, we need to specify that the
partition doesn't get mounted in the file system - we
want to be able to remove it and not have it there at
boot up time. So, select the blank option in 'Mount
|Finally, it looks like this. Note the 'F' in
the column before 'Fat32' - that means that it will
format this partition.
|Repeat the process although, this time, we
choose a ReiserFS format for the partition.
|Note that the start cylinder number has been
inserted automatically - this is a fence-post issue so
507 was the last one of the first partition and 508 is
the first cylinder of this partition. We could, instead
of accepting 1014 as the last, choose a lower number if
we wanted to put further partitions on it but we will
Again, we select no mount point.
|It now looks like this. We are all ready to
|Actually, we haven't done anything to the
drive up until this point. Now, things will change. We
are presented with a list of changes and we can still
chicken out if we want to.
|If the list of things on the right is what we
really want to do, click on 'Finish' (or 'Apply' if there
are other things we want to do later on).
|You can, of course, do these actions one at
a time by clicking on 'Apply' each time.
|If you clicked on 'Apply', you should see
something like the shot on the right. We now have a 125MB
Fat32 partition that is readable by Windows (including
Windows 98SE which works without any fuss with that
partition) and just about any other operating system on
the planet; and a 124.7MB ReiserFS partition that is
readable by Linux. We can now take the drive out and, as
there was nothing written to the /etc/fstab file, next
time we start Linux (sounds a bit incongruous), the
system will not search for that drive and (if it was)
would not then fail to find it and dump you at the
command line so that you can edit the /etc/fstab file
Cheap, supermarket paper is a God-send if you have
children using your printer all of the time but its
quality can vary between 'very good' and 'execrable':
sometimes it feeds and prints beautifully and other times
... well ... forget the ink bleeding through it, you can
read a newspaper through it (yes, you really can).
By definition, a sheet of DIN A4 paper is 1/16th
of a square metre. The standard is that A0 has an area of
1m2 and has a ratio of short to long side
lengths of 1 to the square root of 2 (1:1.414).
If you then slice an A0 sheet in half, it now has a ratio
of 1:0.7071. If you invert it and
multiply it by 1.414, you get 1:1.414 again. This means
that you can slice it in half any number of times and you
always get the same aspect ratio.
To find the area (in square metres) of a sheet of DIN
A paper, the area = 1/2x where x is the number of the paper so,
for A4, 1/2x
is the same as 1/24 or
Paper is sold as a certain weight per unit area -
usually 80GSM which means that one square metre weighs 80
grammes. So, if we know the weight per unit area of the
paper and the area, we can work out how much it should
Nowadays, a ream is 500 sheets so 500/16
= 31.25 m2. If you multiply this by the weight
for a square metre (80 grammes), you get the weight of a
ream which is, for 80GSM, 2.5kg. For 70GSM, it is just
Normally, you would find 80GSM but card is usually
120GSM (or even heavier, depending upon your intended
purpose) and 'Bank' paper is 40GSM (this is really light
and used for typing records on where you have a lot of
records to keep using as little weight of paper as you
can get away with). You can also get 75GSM and 70GSM
which have advantages if you are putting manuscripts
through the post as every gramme saved works out cheaper
So, when is 80GSM paper not 80GSM? Arguably, you could
claim that if it worked out at 75GSM, it wasn't within
the 80GSM range any more but quite a lot of the weight of
paper is actually water and if you keep paper badly - in
too dry an environment for too long - it can lose water
and therefore weight. As an experienced paper purchaser
myself, I would argue that if a ream of 80GSM clocked in
at 2.2kg, it was well out of range and should be called
So, if you are thinking of buying some cheap,
supermarket paper, get a ream of it and weigh it on one
of the sets of scales in the fresh veg section or get one
of the cashiers to weigh it at a spare checkout.
Paper is effectively sold by weight so if your ream of
80GSM paper weighs in closer to 70GSM, it is a Weights
and Measures issue that needs to be addressed as it could
be construed as 'passing off'.
Sendmail in programs - Sending mail
|Sendmail is one of those programs that is
The screenshot on the right shows
a typical session. First of all, you call it using its
full path (which is normally /usr/lib although it can be
in other places) and then, use the 'From:', 'To:',
'Subject:' and any other lines you need ('Cc:' and 'Bcc:'
for instance) and then, leave a blank line (if you use
the '-t' switch: see 'man sendmail' on the command line
or click here man://sendmail
for more details).
Next, you type in your message and then, when you have
finished, you put a full stop on a line on its own
(nothing before or after it) and then press [Enter].
Sendmail then sends the email for you.
|Even if you can't get to your computer but
you can log into it, you can still use Sendmail because
it is used from the command line. The session in the
screenshot on the right is taken from a Windows98SE
machine using an ssh session.
You can see that exactly
the same thing happens.
So, we know that we can send emails using it and that
it is interactive but how do we send an email from within
|Here's how to do it in Perl.
# This demonstrates how to get one of the methods of how to get your
# programs to send emails to you. You might want to do this if you
# have a daemon that monitors something and needs to get in touch
# with you - perhaps sending a report automatically on a daily basis.
# Let us assume that we already have the message that we want to send
# from the rest of your program in the following scalar:
$content = "Put the text from your program in here - you could just
have this string end here and then concatenate your report
or message to it in another line of code. There is more
than one way of doing it.\n";
# The rest of this program should be static as the only thing you are
# going to get the program to do is to change the above message.
# Start off by creating the message in the $msg scalar.
# Note that you need to have a 'From:', a 'To:' and a 'Subject:' line.
# You can also use 'Cc:' and 'Bcc:'
# Next, you need to leave a blank line and then your message.
# With sendmail, you can use the '-i' switch when inputting from a
# program because sendmail will know when the end of the file is. Otherwise,
# you need to have a dot on its own as the only character on the line to
# signify the end of the message (in the same way that you would if you
# were using sendmail from the command line.
# Note that we are using 'EOF' to terminate the string. You can use
# anything - especially if it is likely to crop up in your string
# anyway. Remember that this will be computer generated so you don't
# need to interact with it once you have written it - you just need
# to be able to make sense of it when you need to edit it - such as
# if you change your configuration.
# Note that the @ characters have to be escaped because this is
# equivalent of using "" rather than ''
$msg = << "EOF";
From: Monitoring daemon <yourname\@yourisp.com>
To: your name <yourname\@yourotherisp.com>
Subject: daemon daily report
# Next, add the message to the header
$msg .= $content;
# Unremark the following two lines if you want to check that the
# string that the program is producing is working all right.
# next, open up sendmail and send it the string. Note that you might have to
# change the location of sendmail if it is in a different place.
# If you want to change the options that you send to it, look them up on your
# system by using 'man sendmail'.
open (SM, "|/usr/lib/sendmail -t -i");
print SM $msg;
close (SM) or warn "Sendmail sent a warning.";
# and that is it. If you take out all of the comments, you have a nice
# little program fragment that you can add to your own work and increase
# its functionality.
|Note the lines...
open (SM, "|/usr/lib/sendmail -t -i");
print SM $msg;
close (SM) or warn "Sendmail sent a warning.";
By opening sendmail - complete with any command line
arguments that it needs such as -i so that it looks for
an EOF rather than a '.' - as a pipe, we can print to it
and when we close it, we effectively send it the EOF that
it is looking for.
Although this is in Perl, it is easy enough to
translate it to any other programming language.
Sub-Pixel Hinting a.k.a.
Sub-pixel hinting has been around for a while but only
recently has the price of flat-screen monitors come down
so that a substantial proportion of the user population
can enjoy them.
So, how good is it really? In Microsoft's press
release (Autumn 1998), it stated 'ClearType improves
display resolution by as much as 300 percent and works
especially well on existing LCD devices, including
desktop flat panels, laptops and smaller devices such as
Handheld and Palm-size PCs.'
Okay, so Microsoft's PR people don't know how to do
the maths because a 300 per cent improvement would mean
it was 4 times as good but, as you will see below, it
could, at the most be only 3 times as good, hence an
improvement of resolution by 200 per cent. So, taking
that into account, can it be three times as good?
- One problem is the fact that the red and the blue
are not perceived as being as bright by the eye
which means that they cannot produce a sub-pixel
effect that is as good as the green sub-pixel.
Very roughly, the perceived brightness of red
added to that of blue is around that of green so
there goes another 100 per cent.
- Often, you'll see sub-pixel hinting examples
where the lines in the original are all 1 pixel
wide so that there is no colour cast added to the
line when the line is hinted. In reality,
one-pixel-wide lines do not happen with any great
frequency - especially with fonts - so you will
most likely see added colour casts to your
letters. Vertical lines such as those in 'l's,
'I's and 'T's, and even the shorter lines in
'm's, 'n's and 'p's will generate a cast that is
uniform along their length so you might end up
with a 'T' with a red or blue vertical line.
- Also, even on a flat-panel monitor, the text is
quite often blurry when it is sub-pixel hinted.
- In addition, your graphics card is now processing
three times as many 'pixels' as it was - a
1024x768 display now has the dimensions 3072x768
pixels so it is more processor intensive (even if
it is your graphics processor, it is still your
- As straight characters often fall foul of
sub-pixel hinting casts, italics are where
sub-pixel hinting really works well. If you only
view italic print then this is for you.
- The Windows version only supports (on XP Home)
horizontal sub-pixel hinting so if you are using
a TFT monitor that you can rotate through 90
degrees so that you can do DTP more efficiently,
you are not supported.
So, does it provide a '300 percent increase in image
resolution'? in a real life environment, 100 percent is
probably as much of an improvement as you will see and
then only if you are completely colour blind (so that the
colour fringes don't irritate you).
Look at these two examples...
|So, if you look over the next few items,
you will learn how it works and can judge for yourself
that if you try it out and you decide that you don't like
it, you will know that it is sub-pixel hinting that you
are blaming rather than something else.
How Sub-Pixel Hinting Works
|This is an
actual TFT display showing the cells.
The cells are so
tiny that you would be convinced that they were square.
|If you are
using a TFT with the cells in order of RGB, you should
see that the distance between the blue and red is a lot
smaller - they might well appear to be touching. You will
see this without using any sub-pixel hinting (which
doesn't affect pixmap images such as the GIF on the
right). In fact, there is a one-pixel-wide line of black
between the red and green, the green and blue and a third
between the blue and red - even though it doesn't look
like it (get a magnifying glass out and look at the
This is, in effect, an example of sub-pixel
hinting (well, shifting stuff around the screen by
amounts smaller than a pixel) because the red displays a
third of a pixel to the left and the blue displays a
third of a pixel to the right, hence the gap being
case you were wondering if it was only red green and blue
it does this with, have a look at this yellow, magenta
and cyan screen - if you think of yellow being the
complimentary colour of blue, magenta of green and cyan
of red, when we have a white line in between, it also
works between the yellow and cyan (complimentary blue and
the mask that we are going to put our text on.
see that it mimics the real screen that is shown above.
the letter we want to put on it - a lower-case 'y'.
can see that we are asking for a hopelessly large amount
of detail to put in there but in reality, you wouldn't
expect much from a small letter like this as long as the
shape made sense in context - a lot of reading is
recognising the overall shape of a word rather than
identifying each letter individually.
what we get. If you almost close your eyes, you can make
out that it is a 'y'.
what it looks like if you add the three colours together
so you have what your eye would expect to see and, at the
scale it is supposed to be at, it looks like this: .
instead of taking the pixel location and finding out how
much of the pixel is covered by a line, we look at each
third of a pixel and see how much of that is covered by
each line, we generate colours instead of grey scale. As
a result of this, you can see in the image on the right
that there appear to be diagonal lines that are only 1
sub-pixel wide - you can see this especially at the lower
end of the y's tail where it is only a blue pixel wide.
|If we look
at the colours generated, we end up with the image on the
right. Note that where there is a horizontal structure
that goes all of the way across a full pixel, the
resulting colour is a grey - as in the horizontal bars at
the top of each branch of the 'y'.
Whilst the colours
in the image on the right might seem to be utterly wild,
a blue next to an orange will, at the pixel level cancel
out to make a grey average over two pixels. However, on
the sub-pixel level they are two dark sides of adjacent
look at the part near to the middle that is orange, blue,
red, you can see in the image above that it is the bottom
of the 'v' part of the y, just above the row where they
If you look at the actual-scale image of the 'y'
below, you can see that the colours have largely
It is when they do not disappear that they can be an
|At the scale it is supposed to be viewed at, it looks
like this: .
If you compare the two, side by side,
they look like this (pixel, then sub-pixel) - .
If you have a TFT monitor, you will be able to see
that the sub-pixel hinting version is a lot clearer if
you ignore the peculiar colours that you sometimes get.
Adding/Removing Sub-Pixel Hinting - Windows
This is done on the default (SP2) installation of
Windows XP home without any plug-ins or toys.
If you want to try out sub-pixel hinting on a Windows
XP machine, this is what you need to do...
'Start'/ 'Control Panel' - note that this step will be
slightly different if you have the other (XP) menu type
but you end up at the control panel display which is
select 'Appearance and Themes'.
click on 'Display'.
have the 'Display Properties' dialogue box.
If you had
the other type of Control Panel display, you could have
got to this stage just by clicking on Display.
Next, select the 'Appearance' tab and then, click on
see the 'Effects' dialogue box. Make sure that the 'Use
the following method to smooth edges of screen fonts:'
(yes, no definite article) checkbox is checked and then
select 'ClearType' from the dropdown combo box.
click on OK
|Following that, click on Apply and you will be able
to see the results...
You can see that the contrast is greatly
reduced and that there are some chromatic aberrations
around the letters. It's a bit like looking at it through
a dirty lens.
case you are wondering to what extent the effect is
there, here it is magnified four times...
You can see
that just about every vertical has been extended into the
pixel on the left (the red line of pixels up the left)
and is an example of poor font placement. This has the
effect of smudging it.
Adding/Removing Sub-Pixel Hinting - Linux/KDE
Like Windows XP above, this is done on the default
installation of KDE without any plug-ins or toys.
all, click on the KDE menu and select Control Center.
this is on KDE 3.1 (this was part of the default
installation at least that long ago) and we are now on
under 'Appearance and Themes', select 'Fonts'.
that, in the 'Anti-Aliasing' frame, check 'Use
anti-aliasing for fonts' and 'Use sub-pixel hinting:'.
that you have four types:
- RGB and BGR cater for normal flat panel screens;
- Vertical RGB and Vertical BGR cater for vertical
screens so that: if you are using either a
flat-panel monitor for DTP and have turned the
screen round by 90 degrees (to the left or the
right - it doesn't matter as you have RGB and BGR
in the vertical option); or, if you are using a
small computer with a vertically oriented screen
- say for reading an electronic book, you can do
|On KDE, Horizontal RGB looks like this:
case you reckon that in the second one, it isn't there,
here it is, magnified four times...
You can see that
the font placement is a lot better than in Microsoft's
version. The contrast between the vertical bars and any
adjacent smudging is far greater so any smudging is only
minimal - this is largely down to the choice of a better
font and better font placement to start with.
With other fonts at the right (wrong) size, the effect
is just as psychedelic as in the Microsoft version.
However, if you do want it, you can - with the KDE
version - use it with any flat-panel display regardless
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