76 LXF249 May 2019 http://www.linuxformat.com
TUTORIALS Vector graphics
Ofcourse,tobedisplayedonscreen,it doeshave
toberenderedaspixels– asit alsohastobeif it’s
printed– butthebasicdefinitionisjusta smallamount
ofdata.Thishashugeadvantageswhentheboxis
editedordeleted.If a boxisdefinedpurelybyitspixels,
addingthatboxtotheimageobliteratesthepixelsthat
hadpreviouslybeeninitspositiononthepage.If you
theneditthebox’sshape,it isn’tpossibletoreinstate
thepixelsthatformerlyoccupiedthatareaofthe
image.If youremovea boxstoredasitsbasic
parameters– a vectorgraphic– ontheotherhand,
thecompleteimagecanberecreatedusingthe
definitionsofalltheremainingobjects,withnolossof
information.Youcanthinkofit asdestructive(bitmap
editing)versusnon-destructive(vectorgraphics).
Vectorgraphicseditorsusuallyprovidea degreeof
supportforbitmaps– paradoxically,youmightthink.
Inmostcases,though,theydon’tprovidethesame
extensivefacilitiesforeditingbitmapsasphotoediting
softwaredoes.Ofprimaryimportance,though,bitmaps
aretreatedjustliketheobjectswe’vealreadylookedat,
soyoucanadjusttheirsizeandpositionandrotate
them.It’snotdifficulttoimaginehowtheinclusionof
bitmapped images could brighten up a basic line
drawing. For example, a diagram illustrating the
electronic control system in a car could certainly benefit
from using pictures of the engine, gearbox, wheels and
so on, instead of just plain boxes with text labels.hotoeditingpackages,alsoknownas
paintingapplications,arewidelyused,but
ofteninappropriately.They’refarfromidealfor
producingdiagrams,flowcharts,logosandillustrations
forscientific,technicalandbusinesspurposes.Instead,
thetoolofchoiceforthissortofjobisdrawingsoftware,
otherwiseknownasvectoreditingsoftware.InLXF248
weranaRoundupoffivevectorgraphicsofferings,all
ofwhicharefreelyavailableunderLinux,andmostof
whichareopensource.
Herewe’reofferingsomehands-onguidanceonhow
touseoneofthesetoolsfora fewtypicalapplications:
LibreOfficeDraw, whichisa verycapablepackage.
Ironically,youmightthink,ourchosentoolisn’ttheone
whichscoredthetopspotinourreview.Howeverwe
believeit offersallthatmostusersneed.Inaddition,
LibreOfficeDrawisprobablyalreadyinstalledonyour
PC,andit’lleasilyworkinconjunctionwithother
LibreOfficetoolsbecauseofthecommonalityoffile
formats.Evenif youchoosetousedifferentsoftware,
manyofthebasicprinciplescoveredherestillapply.Vectoreditingprinciples
Before starting with any hands-on instructions, it will be
helpful to discuss, in broad terms, what vector editing
software provides and how it’s fundamentally different
from paint software, which can also be thought of as
bitmap-editing software. Although paint software now
offers some of the facilities that were previously the
sole domain of vector editing software, this type of
package operates primarily at the level of individual
pixels. While editing pixels is the obvious way forward
for photos – which are, after all, nothing more than a
bunch of pixels – for diagrams, the vector approach of
working with objects is much more appropriate.
In referring to objects, we mean mainly geometric
shapes such as lines, boxes, circles and text, all of
which can be further defined by the colour and
thickness of any outlines, and the colour of any fill.
What makes the vector approach so valuable, though,
is what happens when you draw an object such as a
box. Instead of it being stored internally as a set of
pixels, it’s defined by its position, its width, its height,
its rotational angle, the width and colour of its outline
if any, the colour of its fill and so on.Creating diagrams
and illustrations
There’sa muchbetterwayofcreating technical and business diagrams
andillustrationsthanwitha paintpackage, as Mike Bedford demonstrates.
MikeBedford
The content of a
document might
be paramount,
but Mike reckons
that appearance
is vital to make a
good impression.
Or at least that’s
his excuse for
being obsessed
with drawing
software.
P
LIBREOFFICE DRAW
OUR
EXPERTDimensioning
showsthesizes
ofobjectsas
theyappearon
thepage– so
nothinglarger
than210mm
horizontally
onanA4page.
Thisisn’tvery
usefulif you’re
designinga
kitchen,so
usethescale
optionsto
adjustthis.For engineering illustrations, room layouts and similar mechanical
drawings, the dimensioning feature ensures that dimensions remain
correct following any size changes.