Pixels

• Computing
• Lower Secondary (Key Stage 3)

Pixels

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

How is this made?

Images are made up of bits of data called pixels. Pixels are the smallest unit of a digital image. Each pixel is a small square that contains a colour.

The combination of pixels creates the whole image.

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

12 * 19 = 

resolution of 

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.

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.

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. 

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

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

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.

Instructions:

Step 1

Create a picture by colouring the individual picture elements in the rectangular grid on the top half of the activity sheet.

You can use one of the available grids (8⨉8, 12⨉12, and 16⨉16), or a part of one of the grids (e.g. 6⨉14 on the 16⨉16 grid).

You can use at most four different colours, but you cannot use more than one colour in a picture element, and you cannot leave a picture element without a colour.

Step 2

Use one or two binary digits to represent the colour of each element.

You can:

Decide which binary digit (or pair of binary digits) corresponds to which colour

You cannot:

Use one binary digit for some colours and two for others — you must use either one or two binary digits for all colours.

One thing I learned this lesson was

one thing I dislike about this lesson was?

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

😒🙁😐🙂😃