← ACARA Digital Technologies Years 7–8

Comparing raster and vector images

Raster images store a colour number for every pixel and blur when enlarged; vector images store shape instructions and stay sharp at any size.

Part of: ACARA Digital Technologies Years 7–8 — Representing Text, Images and Sound — Module 45

Understanding Comparing raster and vector images in ACARA Digital Technologies Years 7–8

What it does: A photo has millions of small colour changes. A raster image can store each one as a pixel colour number, which shapes alone cannot do. A logo is made of simple shapes such as rectangles and circles. A vector format like SVG stores those shapes as instructions, so the logo stays sharp when resized. Zooming in makes the pixels bigger, so you see blocky squares. There is no extra detail stored to fill in the gaps. The computer recalculates the shapes at the new size, so the edges stay crisp at any zoom level.

Common mistakes: Photos are usually raster images because they need a colour for every pixel. It should be photo_type = 'raster'. Vector images store shape instructions, not pixel colours. It should be stores = 'shape instructions'.

Class: _____________________ · Name: _____________________ · Date: _________

Free printable worksheet with full answer key — or add this module to a class and your students practise it interactively.

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This module's key terms are also in a printable crossword (Modules 153–172) and word search (Modules 153–188).

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Each concept is reinforced from every angle — learned, then applied, then tested.

Learning

Duo

What does a raster image store?

Instructions for drawing shapesA colour number for every pixel

Matches

zoom(photo.jpg, 800%) -> stays sharp

↓

A photo is a raster image. Zooming in enlarges its pixels, so it gets blurry or blocky and does not stay sharp.

Applying

Meanings

Term

raster vs vector

Meaning

Raster images store a colour number for every pixel and blur when enlarged; vector images store shape instructions and stay sharp at any size.

Practice

Testing

Gaps

< cx="50" cy="50" r="40" />

Check Answer

Spots

1photo_type = 'vector'

2stores = 'colour per pixel'

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Quick Questions

1. What does a raster image store?

A. A colour number for every pixel ✓

B. Instructions for drawing shapes

Raster (bitmap) images are grids of pixels, and each pixel has its own colour number. Vector images store shape instructions.

2. What does a vector image store?

A. Shape instructions, like a circle with a size and colour ✓

B. A long list of pixel colours

Vector images are made from instructions for shapes, lines and colours. The computer redraws the shapes whenever it displays them.

3. You zoom in a lot on a raster photo. What happens?

A. It stays perfectly sharp

B. It looks blurry or blocky ✓

Zooming in makes the pixels bigger, so you see blocky squares. There is no extra detail stored to fill in the gaps.

4. You zoom in a lot on a vector logo. What happens?

A. It turns into blocky squares

B. It stays sharp and smooth ✓

The computer recalculates the shapes at the new size, so the edges stay crisp at any zoom level.

5. Which type of image suits a photo of your pet?

A. Raster ✓

B. Vector

Photos have millions of tiny colour changes. Raster images can record each one pixel by pixel, so they suit photos.

Match the Pairs

<circle cx="50" cy="50" r="40" fill="red"/> → A vector image stores a shape instruction like this, so it stays sharp at any size.

pixel(2,3) = 255,0,0 → A raster image stores a colour number for every pixel, so it blurs when enlarged.

Photos suit raster images because every tiny detail needs its own pixel colour → photo.jpg = raster: one colour number per pixel

Logos and clip art suit vector images because a few shapes can describe them and they scale cleanly → <svg><rect width="80" height="40"/></svg>

zoom(photo.jpg, 800%) -> stays sharp → A photo is a raster image. Zooming in enlarges its pixels, so it gets blurry or blocky and does not stay sharp.

logo.svg stores a colour for every pixel → An SVG logo is a vector image. It stores shape instructions, not a colour number for each pixel.

Key Term

raster vs vector

Raster images store a colour number for every pixel and blur when enlarged; vector images store shape instructions and stay sharp at any size.

Fill in the Blanks

1. <circle cx="50" cy="50" r="40" />

Hint: Type the SVG shape tag that describes a round shape. Vector images store shape instructions like this.

2. <rect x="10" y="10" width="80" height="40" />

Hint: Type the attribute that sets how wide the rectangle is. A vector stays sharp because it stores sizes, not pixels.

3. FOR EACH pixel IN image STORE colour_number

Hint: Type the name of the tiny square unit that a raster image stores a colour number for.

4. <svg width="100" height="100"> <circle r="40" /> </svg>

Hint: Type the tag name that wraps a vector image file (a common scalable format for logos).

5. IF zoom > 100 AND type = "raster" THEN DISPLAY "Blurry pixels"

Hint: Type the comparison operator that checks if the image is enlarged beyond its normal size.

Spot the Error

Question 1

A photo_type = 'vector'

B stores = 'colour per pixel'

C enlarged = 'blurry'

Line A — Photos are usually raster images because they need a colour for every pixel. It should be photo_type = 'raster'.

Question 2

A logo_type = 'vector'

B stores = 'pixel colours'

C enlarged = 'sharp'

Line B — Vector images store shape instructions, not pixel colours. It should be stores = 'shape instructions'.

Question 3

A photo = 'raster'

B zoom_in(photo, 800)

C result = 'sharp'

Line C — A raster photo has a fixed number of pixels, so zooming in makes it blurry or blocky. It should be result = 'blurry'.

Question 4

A logo = 'vector'

B zoom_in(logo, 800)

C print('Zoomed in')

D result = 'pixelated'

Line D — A vector logo is redrawn from its shape instructions at the new size, so it stays sharp. It should be result = 'sharp'.

Question 5

A <svg width="80" height="80">

B <circle cx="40" cy="40"

C r="30" fill="red" />

D </sgv>

Line D — An SVG vector image is written as shape instructions and must end with the matching closing tag. It should be </svg>.

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