Graphic Design Essentials

VECTOR GRAPHICS:
A vector drawing is one that is made of nothing more that a series of lines connected at control points. These lines can be curved or straight. The control points are called nodes or anchor points. The inside areas bounded by lines and nodes can be filled with color.
Vector drawings are stored by the computer as simple formulae, these take up far less of the computers resources than do bitmaps, and make much smaller files when saved.
Traditionally Vector images are used for Logos and line work Graphics. They give a very sharp crisp print.
Vector drawing can be extremely detailed and complex with graduated fountain fills and can be almost photographic. The really great thing about Vector Images is that they can be scaled to any size without sacrificing quality have a look at the image below to see how a Vector image is made up of a collection of shapes.

Bitmap Programs such as The GIMP are ideal for working with Photographic Images and also for providing their own unique special effects that can not be preformed on Vector Graphics Programs.
Vector Graphics Programs such as Inkscape can also Incorporate Bitmaps into a Finished Artwork that combines Vector and Bitmap Images together. They also have filters for applying effects to Bitmaps from within the program allowing a certain degree of Bitmap editing without leaving the Illustration Program.
These programs also incorporate Trace programs that can convert a Bitmap Image into a Vector Image. You can follow one of our Inkscape Tutorials showing you how to do this.

About Compression and File Types:
It is essential to understand the difference in file types, particularly when you are dealing with photographic Images intended for high quality publishing.
bmp, jpeg and tiff are the most common file types used for Bitmap or Raster images.
Tiff and Bmp files faithfully store the information about every pixel, maintaining the quality of the Image but in doing this they create large files that can take up space on your hard drive or storage device. For a really high quality Image suitable for Publication it is always best to maintain high quality 300 dpi images.
Jpeg files use compression to make the file smaller. Jpeg files are very suitable for creating artwork for the Web but because of the compression the file quality can be severely compromised depending on how much compression you use. Instead of storing information on every pixel, jpeg files use a formula that groups pixels together.

If you are using a Digital camera remember that by default most cameras use jpeg compression. Set your camera to 'Raw' for the best quality images. It really depends on what you plan to do with the image in the end. If you want to view it on a screen then jpeg compression is fine. Most digital camera jpegs will also print a good 6 x 4 high gloss photo, but not so good if you intend to have a shot enlarged for framing. Again you should set your camera to 'Raw'.

PNG &SVG FILES:
.Png files also use compression, they also allow transparent backgrounds which jpeg files don't. Inkscape uses .png files to export Bitmap artwork. I find .png files less 'lossy' than jpeg files although slightly larger in file size. Png files are very suitable for creating artwork for the Web.
Svg files are Vector Graphic files. Inkscape uses this file type as default. All of the Vector elements are maintained and the Image can be scaled up or down with no loss of quality. Svg files can now be viewed in the latest browsers on the Web. Vector graphic files are typical much smaller than bitmap files.

PDF files:
Pdf files were created by Adobe to provide a standard file format that encapsulates both bitmap, vector and text elements in a format that can be opened by anyone with a pdf viewer. You can embed typefaces and also choose to add compression to make files smaller for the Web.
Inkscape allows you to save your files using the Pdf format.

GIFF files:
Giff files are used primarily for the web, they make an Images file size smaller by reducing the color palette. giff files also support animation and can have transparent backgrounds.

PS & EPS files:
There are many other file types which Inkscape supports including .ps (postscript) and .eps (encapsulated postscript) . Saving files in these formats allows you to open the file in other programs such as Corel Draw and Adobe Illustrator. I have found Illustrator opens the native .svg files with no problems

BITMAP or RASTER GRAPHICS:
Bitmap is the term used to describe a Digital image that is constructed as a series of squares by a Computer or a Digital Device (such as a Scanner or Digital Camera). These squares are called pixels. Each pixel has its own numerical code which records information such as the color, size and position of the square. The pixels are usually small and not apparent to the naked eye. These number of pixels in a given area determine the quality of the Image. File sizes are measured in ppi (pixels per inch) or dpi (dots per inch). Even though dpi is really a printer term referring to printed dots.
As a rule 72dpi (72 pixels per square inch) Images are good for the Web because the files are small but these files are no good at all for publishing they are to low a quality.
Images to be used in Publications should be 300dpi or better. An image of 150 dpi or 200dpi is a good option if you intend to print larger than A4 on your Inkjet or Laser printer.
If you get an image that is low resolution i.e. 72ppi and enlarge that image, it will become more and more fuzzy the larger you go until you can actually see the pixels.