Y8 - Image Binary

• Computing
• Lower Secondary (Key Stage 3)

Y8 - Image Binary

How do you think a computer stores an image?

Bitmaps

Pixel based

each pixel stored as a binary number

pixelate when enlarged

Vector

coordinate based

uses calculations

will not pixelate

Vector Use

Bitmap use

VECTOR

BITMAP

Uses calculations

smaller in file size

larger in file size

will pixelate

uses pixels

Used for real photos

Will not pixelate

Used for maps

Bit depth

How many bits allocated per pixel

1 bit vs 2 bit

How many bits per pixel is the standard in modern computers?

RGB 24 bit colour

24 bits per pixel

8 for red

8 for green

8 for blue

16.7 million options

one pixel of pure green would be 000000001111111100000000

Hex makes it easier

6 digits of hex

instead of 24 binary digits

Easier to remember

Easy to convert to binary

• 000000 = black
• FFFFFF = white
• 960080 = lilac

Try this

Put this number into google

#642240

What do you think it is?

Can you remember Hex to binary conversion?

Convert 642240 into binary

skills video

comparison

The school want a printing company to make several leaflets to advertise a school open evening event.

They could say...

"Use colour #642240"

or

"use 011001000010001001000000 !!!"

How many colours could you represent using a bit depth of 3

1. 3
2. 4
3. 8
4. 16

How many colours could you represent using a bit depth of 8

1. 8
2. 64
3. 255
4. 256

How many bits are assigned per channel in RGB 24 bit

1. 4
2. 8
3. 12
4. 24

How many digits of hexadecimal are needed to represent a 24 bit colour

1. 6
2. 8
3. 4
4. 1

Image resolution

Number of pixels across the height and width of the image

Density of pixels in a given area (usually dots per inch)

Challenge

Research the term "metadata" when linked to storing images

get some examples

Examples of metadata for a stored image

Impacts

What do you think happens when you increase either the resolution and/or bit depth for an image?

Extension

The need for compression:

open and have a read over this (includes video)