Be able to resize an image as specified to maintain or adjust the aspect ratio of an image

Topic 12 – Images (Cambridge IGCSE ICT 0417)

Learning Objective

Be able to place, resize, crop, rotate and reflect an image, and to maintain or adjust its aspect ratio as required.

12.1 Placing an Image with Precision

Accurate placement is essential for professional‑looking documents, presentations and web pages.

• Inserting the image

  • Microsoft Word / PowerPoint: Insert → Pictures → This Device…
  • Google Docs / Slides: Insert → Image → Upload from computer
  • Paint, Photoshop, GIMP: File → Open… (or drag‑and‑drop).

• Alignment tools

  • Alignment buttons (left, centre, right, top, middle, bottom) on the Layout or Home ribbon.
  • Word/PowerPoint: Align → Align to Page/Slide for exact positioning.
  • Distribute horizontally/vertically to space several images evenly.

• Text‑wrap settings

  • Square, Tight, Through, Top‑and‑Bottom, Behind/Above Text – choose the style that best fits the layout.
  • Word: right‑click the image → Wrap Text → select the desired option.

• Ruler / Grid for precision

  • Show the ruler (View → Ruler) and drag the image until the required X‑ and Y‑coordinates appear.
  • Turn on gridlines (View → Gridlines) and snap the image to a grid intersection for consistent spacing.

12.2 Resizing an Image – Maintaining or Adjusting Aspect Ratio

What is Aspect Ratio?

The aspect ratio describes the relationship between an image’s width and height.

Formula (decimal) Aspect Ratio = width ÷ height

Formula (fraction) If the ratio is given as W : H, then

 new height = new width × (H ÷ W) or new width = new height × (W ÷ H)

Example: 800 px × 600 px → 800 ÷ 600 = 1.33 (≈ 4 : 3).

Why Keep the Aspect Ratio?

• Preserves the original shape – no stretching or squashing.
• Prevents distortion that looks unprofessional.
• Ensures the image fits correctly in documents, presentations or web pages.

Calculating New Dimensions (maintaining the ratio)

1. Determine the original aspect ratio (as a decimal or fraction).
2. If the new width is known:
   

   new height = new width ÷ aspect‑ratio (decimal)
   or new height = new width × (height ÷ width) (fraction).

3. If the new height is known:
   

   new width = new height × aspect‑ratio (decimal)
   or new width = new height × (width ÷ height) (fraction).

Step‑by‑Step Example (maintaining ratio)

1. Original size: 1200 px × 800 px → aspect‑ratio = 1200 ÷ 800 = 1.5 (or 3 : 2).
2. Required width: 900 px.
3. New height = 900 ÷ 1.5 = 600 px (or 900 × 2 ÷ 3 = 600 px).
4. Resulting size: 900 px × 600 px – still 3 : 2.

Percentage‑Based Scaling (exam‑style)

• Many programs allow you to resize by a percentage (e.g., 50 %).
• When “Maintain aspect ratio” is active, the same percentage is applied to width & height automatically.
• Example: an image 800 px × 600 px resized to 75 % → 800 × 0.75 = 600 px, 600 × 0.75 = 450 px.

Adjusting the Aspect Ratio (when a different ratio is required)

• Crop the image – removes part of the picture, keeping the remaining pixels unchanged (lossless).
• Stretch / compress – changes width and height independently; usually avoided because it distorts the picture.

Practical Methods in Common Software

12.3 Cropping an Image (Changing Aspect Ratio without Distortion)

Cropping removes unwanted edges and changes the aspect ratio while keeping the remaining pixels unchanged.

General Steps (most programmes)

1. Select the image.
2. Choose the Crop tool (scissors icon in Paint, Crop button in Word/PowerPoint, Crop Tool in Photoshop/GIMP).
3. Drag a rectangle over the part you want to keep. Use the “Aspect Ratio” lock (e.g., 4 : 3) if a specific ratio is required.
4. Press Enter or click Apply to confirm.

Non‑destructive cropping (Office 365)

• Word/PowerPoint keep the original image hidden; you can restore it with Picture Format → Reset Picture.
• This is useful for AO3 evaluation questions – you can discuss the advantage of non‑destructive editing.

Software‑Specific Tips

12.4 Rotating an Image

Rotation changes the orientation without altering pixel data.

12.5 Reflect (Flip) an Image Horizontally or Vertically

Flipping creates a mirror image – useful for symmetry or correcting orientation.

Quick Checklist before Flipping

• Do you need a mirror image for design symmetry?
• Is the image currently upside‑down or reversed (e.g., scanned text)?
• Will flipping affect readability or meaning? (e.g., text becomes backward.)

12.6 Image Resolution & File Formats (Essential Knowledge)

Resolution (DPI) vs. Pixel Dimensions

• DPI (dots per inch) determines how large an image prints. Screen size is controlled by pixel dimensions; DPI is ignored on‑screen.
• Typical print requirements:

  • 300 dpi – high‑quality colour prints (flyers, brochures).
  • 150 dpi – large‑format prints where viewers stand back.

• Conversion formula: pixels = centimetres × DPI ÷ 2.54 (because 1 in = 2.54 cm).

Choosing the Right File Format

Saving After Editing

• Always save a copy of the original before cropping, resizing, or changing format.
• When an exam question asks for a specific format, use Save As… and select the required type.

12.7 Optional Extension – Adjusting Colour, Brightness & Contrast

These features are not part of the core IGCSE ICT assessment but may appear in higher‑order questions.

• Microsoft Word / PowerPoint: Picture Format → Corrections (brightness/contrast) or Color (saturation, recolour).
• Adobe Photoshop: Image → Adjustments → Brightness/Contrast, Levels, Hue‑Saturation.
• GIMP: Colours → Brightness‑Contrast, Hue‑Saturation.

Quick Reference – Common Aspect Ratios

Common Pitfalls & How to Avoid Them

• Forgetting to lock the ratio – always verify “Maintain aspect ratio” (or “Lock aspect ratio”) before resizing.
• Relying only on percentage scaling – rounding can produce off‑by‑one‑pixel errors; calculate exact pixel values when precision matters.
• Changing DPI unintentionally – DPI affects print size, not on‑screen size. Keep DPI constant unless a specific print requirement is given.
• Destructive cropping – keep an untouched copy of the original image; use non‑destructive cropping where possible.
• Choosing the wrong file format – select JPEG for photographs, PNG for graphics with transparency, and always save a master copy in a lossless format.

Self‑Assessment Questions

1. An image is 1920 px × 1080 px. What will be its height if you resize the width to 1280 px while keeping the aspect ratio?
2. You need an image that fits a 5 cm × 7 cm space on a printed flyer at 300 dpi. What pixel dimensions are required?
3. Explain the difference between cropping an image to change its aspect ratio and stretching it.
4. Describe how you would rotate an image 90° clockwise in Microsoft PowerPoint and then flip it vertically.
5. In Word, you want an image to occupy exactly 4 cm × 6 cm on the page. Which two settings must you adjust?
6. When saving a logo with a transparent background for a website, which file format should you choose and why?

Suggested Diagram

Summary

• Place images precisely using insertion, alignment, wrap‑text, and ruler/grid tools.
• Resize images while maintaining aspect ratio using proportion formulas or percentage scaling; know how to adjust the ratio when required.
• Crop to change the ratio without distortion – remember non‑destructive options in Office 365.
• Rotate (90°, 180°, or any angle) and reflect (horizontal/vertical); you can rotate multiple images at once.
• Understand resolution (DPI) and choose the appropriate file format (JPEG, PNG, etc.) for the task.
• Optional colour/brightness adjustments are useful but not required for the core exam.

Always double‑check that “lock/maintain aspect ratio” is active, keep an original copy of the image, verify final dimensions (pixels or centimetres), and select the correct file format before submitting your work.