Justify the use of a bitmap image or a vector graphic for a given task

1.2 Multimedia: Bitmaps vs. Vector Graphics

In this lesson we’ll learn when to choose a bitmap image (like a JPEG or PNG) and when to pick a vector graphic (like an SVG). Think of a bitmap as a photo made of tiny coloured pixels, and a vector as a set of mathematical instructions that draw shapes.

📷 Bitmaps – When to Use Them

Bitmaps are best for:

  • Photographs or realistic images where colour gradients matter.
  • Complex textures that would be too heavy to describe mathematically.
  • When you need exact pixel data for editing in a raster editor.

⚠️ Warning: Scaling a bitmap up can cause pixelation – the image looks blocky. The resolution is measured in pixels per inch (ppi) or dots per inch (dpi):

$resolution = \frac{pixels}{inches} = ppi$

🎨 Vector Graphics – When to Use Them

Vectors shine when:

  • You need to scale the image to any size without losing quality.
  • Designing logos, icons, or illustrations that must look sharp on all devices.
  • Storing simple shapes like circles, rectangles, and lines.

Vectors use mathematical equations to describe shapes. For example, a circle is defined by:

$x^2 + y^2 = r^2$

🖼️ Comparison Table

Feature Bitmap Vector
File Size (small images) Usually larger due to pixel data Often smaller – just equations
Scalability Poor – pixelation when enlarged Excellent – stays crisp at any size
Editing Complexity Pixel‑by‑pixel editing needed Edit shapes, colours, paths easily
Use Case Example Photograph of a cat 🐱 Company logo 🎯

🧩 Decision Flowchart (Text Version)

  1. Is the image photographic or highly detailed? Yes → Bitmap.
  2. Do you need to resize the image many times? Yes → Vector.
  3. Is the image simple (icons, logos)? Yes → Vector.
  4. Otherwise, Bitmap is usually fine.

📚 Exam Tip Box

Exam Tip: When answering “Justify the use of a bitmap or vector graphic for a given task”, remember to:

  • State the task clearly (e.g., “Create a logo that will be printed on T‑shirts”).
  • Explain the key properties of each format (resolution, scalability, file size).
  • Use a comparison table or bullet list to highlight differences.
  • Give a conclusion that directly answers the question.

Example answer structure:

  1. Task description.
  2. Why a vector is suitable (scalable, small file).
  3. Why a bitmap would be unsuitable (pixelation on large prints).
  4. Final recommendation.

🎓 Quick Practice Question

Imagine you’re designing a website banner that will appear on both desktop and mobile devices. Which format would you choose and why? Write a short justification (2–3 sentences).

Revision

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