ImagesData Representation

Objectives

Understand the terms bitmap & pixel

Understand how bitmap images are stored using binary in a computer system

Understand the term metadata and what it is for (height, width, colour-depth)

Types of images

There are two ways in which we can store an image on a computer

Bitmap Image

Vector Image

Looking at Bitmaps in detail

Bitmap images are a collection of pixels arranged in a grid pattern

A pixel is a point on the screen which is made up of 3 different colours – RGB (Red, Green & Blue).

These colours can then make any colour we wish, by mixing them together.

How to represent colour in binary Just like other data colour is represented in binary Colour groups or a collection of colour is called a pallet We can change the number of colours in a pallet by

changing the number of bits that we use of colour.

1 bit2 Bits

4 Bits

2 Possible values

0 = Black

1 = White

4 Possible values

00 = Black

01 = Dark Grey

10 = Light Grey

11 = White

16 Possible

values

0000 = Red

0001 = Orange

……

1110 = Indigo

1111 = Violet

Parts of the image An image will come with two parts

Metadata

Image data

Meta Data

• It specifies the picture’s resolution, i.e 14 px by 14px

• The colour depth (how many pixels are used for the pallet)

Image Data

• This is the binary that makes up the image

• Basically a long string of 0s and 1s

Time to play

It’s now time to have a go at making your own bitmap image using Hama beads