Today we are going to explain the differences between raster graphics and vector graphics for our general public.
Raster graphics images (or bitmaps) are based on the elementary concept of pixel.
A pixel (picture element) is the smallest controllable “dot” or “point of colour” or “unit” of a picture.
Raster images are made of pixels (ordered in arrays or matrices), each pixel having its own coordinates and color, similar to how a mosaic is made out of small pieces of colored glass.
Hence the name “bitmap” used for files : the image is encoded as a “map of bits” holding the position and colour of each and every pixel.
Therefore, a bitmap image is technically defined by its width and height (in pixels) and by the amount of bits-per-pixel used for storing colour information (“colour depth”).
Hence, the greater the quality (resolution ), the bigger the file size.
For that reason, bitmap files can be uncompressed or compressed (either lossy or lossless) resulting in a large variety (including sub-varieties) of popular file formats such as TIFF, BMP, PNG, JPEG, JBIG2, etc.
Vector graphics, on the other hand, do not store image information as pixels.
Instead, they contain mathematical expressions to generate and represent all details of an image.
In other words, it contains description on “how to draw” the image, instead of “what colour each pixel must have in order to obtain the image”.
This approach has 2 main advantages : the image quality remains highest regardless of zooming actions and the file size is about the same no matter the resolution of the image.
Vector graphics use complicated (and often proprietary) algorithms therefore such file formats are generally restricted for use only with the application that generated them (such as AI format for Adobe Ilustrator, .CDR format for CorelDraw, AutoCAD DXF, etc) but this is not an absolute rule.