What I Should Know

Unit 1 – Bitmap Graphics

Use this checklist to review our unit, ticking each box as you go

1. Binary Basics

I’ve reviewed Binary Basics and so I know: Chips are made from circuits that can be off or on Off and on is represented by 0 and 1 This is called binary A single 0 or 1 is called a bit and 8 bits make a byte In a byte, the place values are 128-64-32-16-8-4-2-1 How to use place values to convert binary to ‘normal’ decimal numbers

2. Bitmap Basics

I’ve reviewed Bitmap Basics and so I know: Images such as photos as called bitmaps Bitmaps are made from a grid of pixels Each pixel’s colour is stored as a binary number The number of bits used is called colour depth For example, with 8 bits you can have 256 colours

3. Types of Image Files

I’ve reviewed Types of Image Files so I know: The details about GIF images The details about JPG images The details about PNG images

4. Key Editing Tools

I’ve reviewed Key Editing Tools so I know: The purpose of these tools: Select, Marquee,

Lasso and Magic Wand

1. Binary Basics

Amazingly, all digital devices like PCs and phones handle data such as text and images using binary numbers.

Binary uses just two digits to represent computer chip circuits

where electric signals are either on or off:

0 = off 1 = on

Each single 1 or 0 is called a bit. But you can’t do much with

just one bit!

So we put eight bits together to make a byte.

Binary bytes look confusing but we use place values to convert

them to decimal numbers like this:

128 64 32 16 8 4 2 1

0 0 1 0 1 0 1 0

32 8 2 = 42

dd/mm/yy

+

+

X 2 X 2

2. Bitmap Basics

Images such as photos are called bitmaps. They are made from a grid of tiny squares called pixels. Each pixel’s colour is stored as a number in binary.

0 0 0 0 0 0 0 0

0 1 1 0 0 1 1 0

0 1 1 0 0 1 1 0

0 0 0 0 0 0 0 0

0 1 0 0 0 0 1 0

0 0 1 0 0 1 0 0

0 0 0 1 1 0 0 0

0 0 0 0 0 0 0 0

This example uses just one bit that’s either 0 or 1.

So you can only have 2 colours eg black & white.

To store more colours, you need more bits. This is called

colour depth:

1 bit = 2 colours

2 bits = 4 colours

3 bits = 8 colours

4 bits = 16 colours

5 bits = 32 colours

6 bits = 64 colours

7 bits = 128 colours

8 bits = 256 colours

dd/mm/yy

x 2

x 2

3. Types of Image Files

There are big differences between these types of image files:

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PNG JPG GIF

Colour depth

8 bits 1 byte

Number colours

256 16.8 m 16.8 m

Layers

Trans- parency

Anim- ation

Not smooth

True colour

Editable

layers

24 bits 3 bytes

32 bits 4 bytes

4. Key Editing Tools

These special tools help us edit images in more creative ways.

dd/mm/yy

Select

Marquee

Magic wand

Lasso