← ACARA Digital Technologies Years 5–6

One bit gives two colours

One bit per pixel can only be 0 or 1, so each pixel can only be one of two colours, like black and white. A photo needs many more colours, so it needs more bits.

Part of: ACARA Digital Technologies Years 5–6 — Representing Data with Numbers — Module 17, ACARA Digital Technologies Years 7–8 — Representing Text, Images and Sound — Module 28

Understanding One bit gives two colours in ACARA Digital Technologies Years 5–6

What it does: This key uses blue and yellow, showing that one bit can stand for any two colours you choose. One bit can only separate two colours, so a photo needs more bits for each pixel. A bit is a binary digit, so it can only be 0 or 1. That gives two choices. In this code 0 means white and 1 means black, so 1 is a black pixel. The two values 0 and 1 can stand for any two colours, as long as we agree which is which. The code says 0 is green and 1 is red, so a 0 pixel is green.

Common mistakes: Each bit has 2 possible values, so the number of colours is 2 ** bits. With 1 bit that gives 2 colours, not 3. It should be colours = 2 ** bits. The key says 1 means white, so a pixel of 1 prints white. The comment should say white, not black.

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This module's key terms are also in a printable crossword (Modules 59–71) and word search (Modules 44–71).

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Learning
Duo
How many different values can one bit hold?
Two: 0 and 1Ten: 0 to 9
Matches
1 bit = 3 colours
↓
One bit can only be 0 or 1, so it gives 2 colours, not 3.
Applying
Meanings
Term
1 bit = 2 colours
Meaning
One bit per pixel can only be 0 or 1, so each pixel can only be one of two colours, like black and white. A photo needs many more colours, so it needs more bits.
Practice
bits ← 1
Testing
Gaps
1 bit = colours
Check Answer
Spots
1bits = 1
2colours = 3 ** bits

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Quick Questions

1. How many different values can one bit hold?
A. Two: 0 and 1 ✓
B. Ten: 0 to 9
A bit is a binary digit, so it can only be 0 or 1. That gives two choices.
2. If each pixel uses 1 bit, how many colours can one pixel be?
A. 2 colours ✓
B. 256 colours
One bit has two values, so each pixel can only be one of two colours.
3. A 1-bit picture uses 0 for white and 1 for black. What does a pixel with the value 1 show?
A. A white pixel
B. A black pixel ✓
In this code 0 means white and 1 means black, so 1 is a black pixel.
4. Can a 1-bit image use blue and yellow instead of black and white?
A. No, it must be black and white
B. Yes, any two colours can be the pair ✓
The two values 0 and 1 can stand for any two colours, as long as we agree which is which.
5. A pixel is stored as 1 bit. Which pixel value is NOT possible?
A. 2 ✓
B. 0
One bit can only be 0 or 1. The number 2 needs more than one bit.

Match the Pairs

1 bit = 2 colours → One bit per pixel can only be 0 or 1, so each pixel can be one of only two colours.
0 = white, 1 = black → A key that gives each of the two bit values one colour, so every pixel is either white or black.
The two colours do not have to be black and white. Any pair of colours works if 0 and 1 each get one. → 0 = blue, 1 = yellow
A photo has thousands of different colours, so one bit per pixel is not enough to store it. → 1 bit = 2 colours, photo = many colours
1 bit = 3 colours → One bit can only be 0 or 1, so it gives 2 colours, not 3.
0 = red, 1 = green, 2 = blue → A single bit cannot be 2. It can only be 0 or 1, so the key can only have two colours.

Key Term

1 bit = 2 colours
One bit per pixel can only be 0 or 1, so each pixel can only be one of two colours, like black and white. A photo needs many more colours, so it needs more bits.

Fill in the Blanks

1. 1 bit = 2 colours
Hint: Type how many different colours one bit can show.
2. A black and white image uses 1 bit per pixel
Hint: Type the number of bits each pixel needs when it can only be one of two colours.
3. A row of 8 pixels needs 8 bits in total
Hint: Each pixel uses one bit, so type the total number of bits for the row.
4. Colour pair key: 0 = red, 1 = blue
Hint: Type the other binary digit a single bit can be.
5. A photo needs more bits per pixel than 1
Hint: Type the word that says how the number of bits compares, because a photo has many colours.

Spot the Error

Question 1
A bits = 1
B colours = 3 ** bits
C print(colours)
Line B — Each bit has 2 possible values, so the number of colours is 2 ** bits. With 1 bit that gives 2 colours, not 3. It should be colours = 2 ** bits.
Question 2
A key = {0: "black", 1: "white"}
B pixel = 1
C colour = key[pixel]
D print(colour) # black
Line D — The key says 1 means white, so a pixel of 1 prints white. The comment should say white, not black.
Question 3
A # one bit per pixel
B valid = [0, 1, 2]
C pixel = 1
Line B — One bit can only be 0 or 1. The value 2 cannot be stored in a single bit, so the list should be [0, 1].
Question 4
A bits = 1
B colours = 2 ** bits
C if colours == 4:
D print("black and white")
Line C — One bit gives 2 colours, so the check must be colours == 2. Checking for 4 would never match, so black and white would not print.
Question 5
A pixel_values = [0, 1, 2]
B count = len(pixel_values)
C print(count, "colours")
Line A — A 1-bit pixel can only be 0 or 1. Adding 2 would make three values, so the list should be [0, 1].

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