Digital imaging

Digital imaging

Two types of graphic

• Bitmap• Vector

Digital imaging

Bitmap

• Image itself is stored as a map showing the position of each pixel.

• Details of the colour of each pixel are stored.

• This is a huge amount of data.

• Files to store bitmap images are large.

Digital imaging

Vector

• Information about how to draw the image is stored rather than the image itself.

• Stored as a series of equations.• The equations tell the computer how

to draw the parts of the image.• Only instructions/equations are stored,

so file size is small.

Digital imaging

Impact of large file size for bitmap

• Large file size means large upload time (i.e., time to transfer file to a website is large).

• Large file size means download time is large (i.e., the time taken for a user to view the image on a website).

• Files are compressed to reduce file size.

Digital imaging

Other problems of bitmap graphics

• Harder to edit than a vector.

• Image loses sharpness when re-sized.

This bitmap image has been re-sized. The jaggedness of the pixels can be seen.

Digital imaging

Impact of small file size for vector graphics

• Quick upload time.• Quick download time.• Can store lots more images in the

same storage space compared to bitmaps.

Digital imaging

Advantages of vector graphics compared to

bitmap graphics• Small upload/download time.• Easier to edit as you can edit parts of

the image.• Can re-size image without loss in

quality.

Digital imaging

Disadvantages of vector graphics

• Only suitable for images with a limited number of colours.

• No good for images with continuous colours like a photograph.