Resampling – When rotating by 90° most programs rotate without resampling (no loss of quality). Arbitrary angles require resampling; choose “Bicubic” or “Lanczos” for the best result.
2. Flip (reflect) an image
Horizontal flip – mirror left‑to‑right.
Vertical flip – mirror top‑to‑bottom.
Useful for correcting scanned pages or creating symmetrical designs.
3. Resize an image
Two ways to specify the new size
Pixels – exact width × height (e.g., 1200 × 800 px). Best when you need a precise dimension for a web layout.
Percentage – relative to the original size (e.g., 50 %). Handy for quick reductions.
Maintain aspect ratio
Always tick the “Maintain aspect ratio” (or “Lock”) box unless a deliberate distortion is required.
In Paint: Home → Resize → check “Maintain aspect ratio”.
In Photoshop: Image → Image Size → ensure the chain‑link icon is active.
In Word/PowerPoint: drag a corner handle while holding Shift.
Changing DPI (resolution)
Screen images: 72 – 96 dpi is sufficient.
Print images: 300 dpi (or 150 dpi for large posters) is the usual requirement.
Removing metadata reduces file size and protects privacy.
Keyboard shortcuts (where available)
Ctrl + O – Open file (Paint, Word, PowerPoint, Photoshop).
Ctrl + S – Quick save.
Ctrl + Shift + S – Save As.
Ctrl + Z – Undo.
Alt + H, R, R – Rotate right 90° in Word/PowerPoint.
Ctrl + Alt + I – Open Image Rotation dialog in Photoshop.
Ctrl + W – Open Resize dialog in Paint.
Ctrl + Shift + U – Open “Save for Web” in Photoshop.
Common problems & solutions
Problem
Possible cause
Solution
Image appears sideways after rotation
Wrong 90° increment selected
Undo (Ctrl + Z) and choose the correct rotation option.
Blurry or jagged edges after rotation
Software resampled the image using a low‑quality algorithm
Use a “Rotate without resampling” command (e.g., Photoshop → Image → Image Rotation → 90° Clockwise) or select “Bicubic” resampling for arbitrary angles.
File size becomes much larger
Saved in a different format or with higher colour depth
Re‑save using the original format, lower colour depth, or adjust JPEG quality (60‑80 %).
Blank space appears after rotating a portrait image
Canvas size not automatically trimmed
Crop the extra space, or use “Fit Canvas to Image” (Photoshop → Image → Trim).
Image quality drops after several edits
Repeated saving in a lossy format (JPEG)
Work on a lossless copy (PNG or TIFF) and only export the final version as JPEG.
Orientation tag is ignored on another device
EXIF orientation not applied by the viewing software
Rotate the image permanently (not just the tag) and save; or strip the EXIF data before sharing.
E‑safety & copyright (Cambridge syllabus wording)
Only use images you have created, that are in the public domain, or that are licensed under Creative Commons (CC‑BY, CC‑BY‑SA, etc.).
When a licence requires attribution, give credit in the format: Author, Title, Source, licence (e.g., “John Doe, Sunset, Flickr, CC‑BY‑2.0”).
Do not edit or redistribute copyrighted images without permission.
Check file size and format before opening downloaded images to avoid malware.
Open an image in at least two different programmes (e.g., Paint and Word).
Rotate the image:
90° clockwise
180°
Arbitrary angle (e.g., 45°) in Photoshop or GIMP.
Flip the image horizontally and vertically.
Resize the image:
Using pixels (e.g., 1024 × 768 px)
Using a percentage (e.g., 50 %).
Maintain aspect ratio and note the DPI before and after.
Crop the image to remove unwanted borders.
Adjust brightness and contrast to improve visual quality.
Group two images in Word/PowerPoint, or place them on separate layers in Photoshop/GIMP and change their stacking order.
Save the edited image using “Save As”:
Choose PNG for a graphic with text.
Choose JPEG (quality 70 %) for a photograph.
Explain (AO3) how each of the following affects resolution, file size and suitability for screen or print:
Rotation (especially arbitrary angles).
Resizing (pixel vs percentage, DPI change).
File‑format choice (PNG vs JPEG vs GIF).
Identify at least two e‑safety or copyright considerations when using an image sourced from the Internet.
Troubleshoot a common problem (e.g., blurry edges after rotation) using the solutions table.
Summary
Image editing is a core ICT skill for the Cambridge IGCSE 0417 syllabus. Mastery of rotation, flipping, resizing, cropping, brightness/contrast adjustment, grouping/layers, and appropriate saving ensures that students can produce professional‑looking visual material while controlling resolution, DPI and file size. Understanding when to use PNG, JPEG, GIF or TIFF, and how to optimise export settings, links directly to the syllabus requirement for “file‑size control”. Finally, applying e‑safety and copyright rules guarantees responsible and legal use of digital media.
Your generous donation helps us continue providing free Cambridge IGCSE & A-Level resources,
past papers, syllabus notes, revision questions, and high-quality online tutoring to students across Kenya.