What is the primary difference between how vector graphics and bitmap images are stored?

Vector graphics store mathematical equations and geometric properties (like coordinates and radius), whereas bitmap images store a grid of individual colored pixels. This allows vectors to be much smaller in file size for simple illustrations.

Why do bitmap images lose quality when enlarged, while vector graphics do not?

Bitmaps have a fixed number of pixels; enlarging them stretches these squares, causing 'pixelation.' Vectors are recalculated using math at any size, ensuring the edges remain perfectly smooth regardless of the scale.

When should a designer choose a bitmap format over a vector format?

A designer should choose bitmap formats for photographs or images with complex, non-geometric textures and subtle color gradients. Vectors are inefficient for these because they would require millions of tiny mathematical paths to mimic natural detail.

What is a common mistake when trying to convert a high-detail photograph into a vector format?

The resulting file size often becomes significantly larger than the original bitmap. This happens because the software must create thousands of complex mathematical shapes to represent the fine details and color shifts of the photo.

What happens to the file size of a vector graphic when you increase its physical dimensions?

The file size remains exactly the same. Since the file only stores the mathematical instructions (e.g., 'draw a circle with radius $r$'), changing the value of $r$ does not increase the amount of data stored in the file.

Why is it incorrect to say a vector graphic has a 'resolution' of 300 DPI?

Vector graphics are resolution-independent and do not have a fixed pixel count. Resolution only becomes relevant when the vector is 'rasterized' (converted to pixels) for printing or display on a screen.

What is a 'drawing list' in the context of vector graphics?

A drawing list is a set of commands and mathematical parameters stored in the file header. It tells the computer exactly which shapes to draw, where to place them, and what attributes (like color) to apply.

Define 'attributes' as they relate to vector objects.

Attributes are the specific properties assigned to a geometric shape, such as its fill color, line thickness, transparency level, and start/end coordinates. These properties can be edited independently for every object in the file.

What are three common file extensions for vector graphics?

Common vector file extensions include .svg (Scalable Vector Graphics), .ai (Adobe Illustrator), and .eps (Encapsulated PostScript). These formats store mathematical paths rather than pixel grids.

How does the concept of 'relative position' help in vector graphics?

Relative position allows objects to be defined in relation to one another or a central coordinate system. This ensures that if the entire image is moved or scaled, the spatial relationships between the internal shapes remain perfectly preserved.

Revision Notes

AS-Level

Cambridge International Examinations

Computer Science

1. Information representation

Vector graphics

Vector Graphics

Summary

Vector graphics are a method of representing digital images using mathematical equations and geometric primitives such as points, lines, and curves. Unlike pixel-based formats, vector images store the instructions to recreate shapes, allowing for infinite scalability and efficient storage of non-photographic content.

1. Definition & Core Concepts

Vector graphics are digital images created from mathematical formulas that define geometric shapes rather than a fixed grid of pixels. Instead of storing color data for every coordinate, the computer stores the properties of objects, such as the start and end points of a line or the center and radius of a circle.

The fundamental building blocks of these graphics are points and paths, which are manipulated using mathematical equations to form complex illustrations. Because the image is defined by math, the computer can recalculate the visual representation at any size or zoom level without losing clarity.

Comparison between a smooth vector circle defined by math and a pixelated bitmap circle.

2. Underlying Principles

Vector files utilize a drawing list located in the file header, which contains a sequence of commands and parameters required to render the image. This list specifies the geometric primitives to be drawn, their relative positions, and their specific visual properties.

Each object in a vector graphic is defined by its attributes, which include properties like line thickness (stroke), fill color, transparency, and curvature. By modifying these attributes in the drawing list, the entire appearance of an object can be changed without affecting other parts of the image.

3. Methods & Techniques

To create a vector object, a user defines anchor points and the paths that connect them, often using specialized drawing software like Adobe Illustrator or Inkscape. The software translates these user actions into mathematical coordinates and commands that are saved into the file format.

When a vector image is opened, the computer's graphics engine reads the drawing list and renders the image in real-time based on the current display resolution. This process ensures that the image always looks as sharp as the screen allows, regardless of the zoom level or physical dimensions.

4. Key Distinctions

5. Exam Strategy & Tips

6. Common Pitfalls & Misconceptions

Vector Graphics

Summary

1. Definition & Core Concepts

Comparison between a smooth vector circle defined by math and a pixelated bitmap circle.

2. Underlying Principles

3. Methods & Techniques

4. Key Distinctions

The primary difference between vector and bitmap graphics lies in their composition and scalability. While bitmaps are made of a fixed grid of pixels that blur when enlarged, vectors are resolution-independent and maintain perfect quality at any scale.

Feature	Vector Graphics	Bitmap Images
Composition	Mathematical equations/paths	Grid of colored pixels
Scalability	Infinitely scalable	Loses quality (pixelates) when resized
File Size	Small (stores formulas)	Large (stores every pixel)
Best For	Logos, icons, typography	Photographs, complex textures

5. Exam Strategy & Tips

Identify the Use Case: If a question asks for a format suitable for a logo that needs to appear on both a business card and a massive billboard, always choose vector graphics due to their infinite scalability.
Check File Extensions: Remember that common vector formats include .svg, .ai, and .eps. If you see .jpg or .png, those are bitmap formats and will lose quality when scaled.
Understand the Header: Be prepared to explain that the file header of a vector graphic contains the 'drawing list,' which is the set of instructions the computer uses to rebuild the image from scratch.

6. Common Pitfalls & Misconceptions

A common misconception is that vector graphics are always better than bitmaps; however, vectors struggle to represent photorealistic detail. Because every color transition in a vector must be defined by a new shape or gradient, a photograph converted to vector would result in a massive, inefficient file size.

Another error is assuming that vector files have a fixed 'resolution' or 'dimension'. In reality, vector graphics do not have defined dimensions in the file itself; they are only assigned dimensions when they are exported or printed to a physical medium.