Bitmaps

Bitmaps are generally used for photographs and photo-realistic images.

Bitmaps are composed of lots of little dots of colour; these dots form the images you see. The amount of dots governs the quality of the image, more dots give a better quality image. Most monitors, like the one you’re reading this from, have either 72 or 96 dots per square inch (dpi). Another name for these dots is pixels. The word pixel is a compound of picture element.

A major disadvantage with bitmap files is that they are not scaleable. If you change the size of the image, the individual pixels become very apparent around the edge, giving the image a very jagged appearance. Bitmaps are dependant upon the resolution (dpi/ppi) they are created and/or saved at. A higher resolution will produce a larger file on your monitor (and hard-drive), but will print at the original size.

In general, bitmap images do not support transparency. There are specific formats, which do support transparency; they are GIF (Graphic Interchange File) and PNG (Portable Network Graphic). Almost the entire available image editing software supports transparency, however this is only when the image is saved in the software program's native format.

One common misconception is that the transparent areas in an image will remain transparent when an image is saved to another format or copied and pasted into another program. Unfortunately this isn’t the case. A copied bitmap will come with an opaque surround.

Vectors

Vectors are generally used in the generation of illustrations and logos.

Vector graphics are made of lines and curves defined by mathematical objects called vectors. Vectors describe graphics according to their geometric characteristics. You can move, resize, or change the colour of an object or graphic without losing quality.

A major advantage with vector graphics is that they are scalable; they can be resized without loss of quality. All of the lines, curves and shapes that make up a vector image retain their smooth edges, regardless of the size they are reproduced at, or the resolution they were created or saved at. As a result, vector graphics are the best choice for bold graphics that must retain crisp lines when scaled to various sizes; logos, for example.

Because computer monitors represent images by displaying them on a grid, both vector and bitmap images are displayed as pixels on-screen.

Vector images have many advantages, but the primary disadvantage is that they're unsuitable for producing photo-realistic imagery. Vector images are usually made up of solid areas of colour or gradients; this means that they cannot normally produce the gentle naturalistic gradients found in photographs. Recent improvements in the blending capabilities of Vector programs have allowed a much more naturalistic blending and gradient appearance to vector images.

A lot of the vector images tend to have a flat, cartoon-like appearance. Many of today's vector tools allow bitmapped textures to be applied to objects giving them an almost photo-realistic appearance. Coupled with the ability to create soft blends, transparency, and shading that once was difficult to achieve in vector drawing programs, and the results can stunning and memorable.

Vector images are generally created using software. Scanned images, without conversion software, cannot be saved as vectors. It is easy to convert a vector graphic to a bitmap by either exporting or using the ‘save as’ command. One reason for wanting to convert a vector to a bitmap is for publication via the web. To publish a vector on the web as a vector, the most common format is the popular Shockwave Flash file format (SWF); this however needs a Shockwave Flash player to be installed on the end users computer.