Raster vs Vector Images

Last week we went over in class the difference between raster and vector images, and what each is used for.

Raster images, also known as bitmap, are made up of many tiny pixels.These pixels can be any colour or shade. Pixels can be stretched, but this distorts the image. Raster images are typically used when designing for screen.Adobe Photoshop is made primarily to manipulate raster images. JPEG, Bitmap and Gif are all examples of image file types which are raster images.

The density of pixels is referred to as dots per inch. The higher the ratio of pixels within an inch, the better the quality of the raster image. However, high quality images also take up more memory. Raster images can be shrunk and quality will stay good. Quality will suffer if raster images are increased in size. When quality matters, its better to start off with larger than smaller images.

As an example, here is a raster image of a duckling.

Below is the result when the image has been shrunken, stretched again and again multiple times in the Paint program.

As can be seen the quality reduces each time until the image is all but destroyed by the process.

Vector images are created through paths connecting points. Mathematical equations tell the computer how the dots are connected and these describe the image. Vector images do not lose quality when stretched or changed. However, fewer colours to work with. Typically used in print as they can be blown up to huge sizes. CGM (computer graphics metafile) and SVG (scalable vector graphics) are examples of vector file types.

Visual example of vector versus raster:

 

Vector images are designed with points and paths. Bitmap images are made with a series of dots.

Vector images can be better for simple images like this, especially if after creation it must be printed to huge size.

In other uses, like photographs, raster images are better. This is because the level of detail possible is higher.