Big Idea
Images are digital files that can be edited (changed in appearance) or compressed (made smaller for storage and faster transmission). Each technique involves tradeoffs: editing gives you control over how images look, while compression must balance file size against quality loss.
Quick Overview
Image Editing
Changing images by resizing, rotating, cropping, adjusting brightness, and more — to match your purpose.
File Compression
Reducing file size by lowering resolution or colour depth — the tradeoff is quality vs. storage space.
Resolution
Total number of pixels (height × width). Higher = more detail and larger files.
Colour Depth
Number of bits per pixel. Higher = more colours, more detail, larger files.
Image Editing
Image Editing
The process of manipulating images and changing them to suit the user's end goal. This includes changing their size, position, appearance, and how they're arranged with other images.
Think of image editing as having a set of tools available in software like Photoshop, GIMP, or even simpler tools like Paint. You use these tools to reshape, reposition, or adjust images to meet a specific need — whether that's making a photo brighter for a website, cropping out an unwanted person, or rotating a scanned document.
The exam expects you to know about eight key editing techniques. Let's go through each one.
1. Placing an Image with Precision
This refers to positioning an image accurately within a document or other media. It's about exact placement.
- How you do it: Select the image and drag it to the desired location (basic method).
- More precise: Some software offers coordinate-based positioning or alignment tools that let you specify exact pixel positions.
- Real-world example: You're creating a book cover and need a logo to be exactly 50px from the top and 100px from the left. You'd use coordinates or alignment tools to achieve this, rather than dragging by eye.
Practice Question
What is the difference between dragging an image to position it and using alignment tools?
2. Resizing an Image
This means changing the dimensions (width and/or height) of an image.
- How you do it: Select the image and drag its corners or edges to make it larger or smaller.
- Aspect ratio: The ratio of width to height. For example, a photo might be 800px wide and 600px high (aspect ratio 4:3).
- Maintaining aspect ratio: When you resize with aspect ratio locked, the width and height change at the same rate — so a 4:3 image stays 4:3, just bigger or smaller. This prevents distortion (squishing or stretching).
- Ignoring aspect ratio: You can choose to resize freely, which can stretch or squash the image (sometimes intentional, often not).
Analogy: Resizing with Aspect Ratio
Think of a photo frame. If you have a 4×6 photo and want to make it bigger, you can either buy a 8×12 frame (maintains aspect ratio — still looks normal) or squash it into a 10×8 frame (breaks aspect ratio — looks stretched). Maintaining aspect ratio = the photo still looks right.
Aspect Ratio Formula
Practice Question