Summary — Everything In This Chapter
Bitmap images
Made of pixels, each stored as binary. Best for photos. Loses quality when enlarged.
Vector images
Made of mathematical equations and points. Best for logos. Scales perfectly forever.
Positioning & resizing
Placing images with precision, resizing while keeping (or breaking) aspect ratio.
Cropping
Cutting away and permanently discarding unwanted parts of an image.
Rotating & reflecting
Turning an image around a point, or flipping it into a mirror image.
Grouping & layering
Organising multiple images so they move together, or stack in a chosen order.
1. What Is a Bitmap Image?
Think about zooming right into a digital photo on your phone until it looks blocky — that's you seeing the individual pixels. A bitmap image is basically a giant grid of tiny coloured squares, like a mosaic made of thousands (or millions) of little tiles.
Key Definition
A pixel ("picture element") is the smallest single element of a bitmap image. Every pixel is stored as a unique binary code that represents its exact colour.
Because every single pixel needs its own binary code, a bitmap file is really just a huge, long list of colour codes — one for each square in the grid, read left to right, top to bottom. That's why bitmaps are the natural choice for photographs: real-world scenes have millions of tiny colour variations (shadows, gradients, textures) that only a pixel-by-pixel grid can capture accurately.
Zoomed-out photo: Zoomed-in (pixelated):
┌─────────────┐ ┌─┬─┬─┬─┬─┐
│ 🌅 sunset │ --> ├─┼─┼─┼─┼─┤ each square = 1 pixel
│ picture │ ├─┼─┼─┼─┼─┤ each pixel = its own binary colour code
└─────────────┘ └─┴─┴─┴─┴─┘
Why does image quality cost file size?
This is the trade-off examiners love to ask about. The more colours an image uses and the more detail it contains, the higher the quality — but also the more binary data that has to be stored, because there are more unique pixels needing more precise colour codes. A simple bitmap with only 2 colours needs far less data per pixel than a photo-realistic image using millions of colours.
Real-world analogy
A bitmap is like painting a picture using thousands of tiny individual coloured squares (like a mosaic tile floor). If you want more detail, you need more, smaller tiles — and that means more tiles to record and store.
Q1. Explain what is meant by a "pixel", and describe the relationship between pixel colour depth and file size.
Q2. Why is a bitmap image a sensible format for storing a digital photograph of a sunset, rather than a vector?
2. What Is a Vector Image?
Now flip the idea completely. Instead of storing a colour for every tiny square, a vector image stores instructions — mathematical formulas and coordinate points that describe how to the shapes that make up the picture.
Key Definition
A vector image is created from mathematical equations and points. Only the maths needed to reconstruct the image is stored — not individual pixel colours.
For example, to store a circle, the computer doesn't need to remember the colour of every pixel inside it. It just needs to remember:
- Centre point
- Radius — how big the circle is
Exam Tips