Year 9 lesson 2 Pixels

• Computing
• Lower Secondary (Key Stage 3)

Pixels

By the end of this lesson you will be able to record the RGB values of a colour and understand what these values are.

Why do humans use denary instead of binary?

How many bits are in a byte?

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

how many kilobytes are in a megabyte?

1. 1
2. 100
3. 1000
4. 10000

What are images made up from?

The number of pixels is called the resolution. The resolution of an image is calculated the same way as the area of a square:

width * height

resolution = 12 * 19 = 228

By the end of this lesson you will be able to record the RGB values of a colour and understand what these values are.

The TikTok logo on a mobile device has a resolution of 1080*1920 which is 2 million pixels or 2 megapixels. a mega pixel is 1 million pixels.

By the end of this lesson you will be able to record the RGB values of a colour and understand what these values are.

Higher resolution images are great because they have increased image quality, but that comes at a cost to file size. this means the higher the resolution the better the image but it costs more storage, has a higher processing time and loading time.

By the end of this lesson you will be able to record the RGB values of a colour and understand what these values are.

How do we calculate the resolution of an image?

Every pixel as it is a computer image is made of binary digits. remember binary is not about numbers it's how computers represent everything. The fixed number of binary bits used to represent a pixel is called colour depth. 

By the end of this lesson you will be able to record the RGB values of a colour and understand what these values are.

By the end of this lesson you will be able to record the RGB values of a colour and understand what these values are.

0 = white

1 = red

2 colours make up this image, for two colours we need a colour depth of 1. This is because we can use 0 - white and 1- dark blue. We assign the binary values to colours when making our own art, in a computer these values are pre-assigned.

By the end of this lesson you will be able to record the RGB values of a colour and understand what these values are.

By the end of this lesson you will be able to record the RGB values of a colour and understand what these values are.

Look at this image, how many colours does it have? and how would we represent this?

By the end of this lesson you will be able to record the RGB values of a colour and understand what these values are.

What is the colour depth of the image?

2 binary bits, so a  color depth of 2

00	white
01	yellow
10	blue
11	red

Note: if you are using 2 bits you cannot use 1 bit, all bits must be the same not a mix of 1,2 or even 3 bits.

By the end of this lesson you will be able to record the RGB values of a colour and understand what these values are.

What are the individual elements in the image called?

There are 448 individual elements in a image. What is this number called?

What is the colour depth of a four colour image?

How do painters make orange?

In practice, colour is commonly represented using 24 bits. 8 for each colour (red,green,blue) 

An example:

Purple is R240,G53,B230). This is then translated into binary, for example the value 240 - 11110000.

Red - 11110000

Green - 00110101

Blue - 11100110
 

By the end of this lesson you will be able to record the RGB values of a colour and understand what these values are.

By the end of this lesson you will be able to record the RGB values of a colour and understand what these values are.

Representation size:

How many bits are required to represent an image?

Resolution x Colour depth!!!

By the end of this lesson you will be able to record the RGB values of a colour and understand what these values are.

If a picture is 10 pixels x 10 pixels and has red, blue, yellow and green in it. How many bits are needed to represent the image

1. 100
2. 200
3. 104
4. 400

Carry on the completing the worksheet you were given and here is the link for the RGB calculator.

               Click here               

By the end of this lesson you will be able to record the RGB values of a colour and understand what these values are.

What is RGB?

What do computers do with these values?

Overall I feel I learned a little/ a lot this lesson

😒🙁😐🙂😃