Brief guide to graphics
Many clients and, remarkably, some designers fail to understand the
difference between the two primary groups of graphics, "Vector" (also
called "outline" graphics) and "Bitmap" (also called "raster" or "rendered"
graphics). A Vector graphic is one which is built using nodes to map
a series of lines and curves which form an object (a logo, a letter,
a picture, etc). A Bitmap image is a grid of very small coloured squares
called "Pixels" which collectively form the image.
It is worth mentioning in advance, because it is a critical point,
that when we refer to Bitmap and Vector graphics, we are not referring
to any particular file format or extension (such as JPEGs or TIFFS).
Though file formats are typically responsible for saving one type
of graphic or another, the distinction between Vector and Bitmap is
independent of any assigned extension. Thus, while a .jpg file is
always a Bitmap graphic, a Bitmap graphic is not always a .jpg file.
Bitmaps
Bitmap graphics are composed of Pixels, each of which contains specific
color information. A Pixel is minutely small; a single image may be
composed of hundreds of thousands of individual Pixels. Much like
cells revealed from a piece of tissue when seen under a microscope,
these Pixels are only clearly and individually visible when the image
is magnified, as shown below.
Bitmaps are ideal for full colour and photographic images because
of the vast range of colours available in each individual pixel. One
of the main problems faced with Bitmaps is when they are blown-up
to large sizes; because the individual pixels are being expanded it
is often likely that the image may appear blocky, or "pixelated".
To combat this issue, good origination is essential with high resolution
images which can withstand being blown-up to large sizes.
Vector Images
Vector graphics are formed using nodes, or "points", which can be
joined using lines or curves to create any type of shape, and then
filled with colours, tints or patterns. Unlike Bitmaps, which are
stored as a "grid of colours" to create a finished image, Vector graphics
are mathematical creations. For this reason, the programs that are
used to create them save instructions on how the image should be drawn,
rather than how it looks. This is the key difference between the two
types of graphics. Because the computer has a description of how the
image should be drawn, it can be redrawn at any size, in any position,
without losing any quality. A vector graphic resized to 5 or even
50 times its original dimensions is simply reproduced, exactly, at
the new size using mathematics rather than physically expanding the
components of the image. Unlike Bitmaps, Vectors never go blocky regardless
of how big they are blown-up, which is why designers call them "scalable"
graphics.
The price of this scaling flexibility is that Vector images must remain
relatively simple in comparison to Bitmap images. It is impossible
to render the nuances of a photographic image in a vector editor;
as a result, illustrative vector graphics have a distinct look and
feel, even when produced in great detail. The examples below show
Vector artwork, and demonstrate the clean illustrative qualities these
graphics produce:
Conversion issues
With the correct software, any Vector image can be rendered as a Bitmap
image easily. However, converting the other way, from Bitmap to Vector,
isn't always as easy and doesn't always produce good results. Vector
graphics are not ideal for photographic work or similarly complex
images. The second image below is a Vector version of the first image
(which is a standard Bitmap). As you can see, without the "grid of
colours" to carry the wealth of colour depth information, the Vectorized
photograph is reduced to a series of coloured shapes which are far
less detailed.
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