Cambridge IGCSE0417

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Information Communication Technology 0417 Chapter Notes

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In this chapter

  1. 1Placing and Resizing Images
  2. 2Cropping, Rotating, and Flipping
  3. 3Brightness, Contrast and Colour Depth
  4. 4Grouping and Layering Images
  5. 5Reducing Image File Size

1. Placing and Resizing Images

In most software, you can insert an image and then precisely control its position and size. For precise placement, you can use the image formatting options to set its position relative to the page margins or anchors in the text, often specified in cm or inches from the top and left edges. Resizing an image changes its dimensions. To maintain the original proportions and avoid distortion, you should always drag the corner handles. Dragging the side or top/bottom handles will stretch or squash the image, changing its aspect ratio.

Key term

Aspect Ratio: The proportional relationship between the width and height of an image.

Examiner insight

Examiners look for precision; when asked to place an image at specific coordinates, state the values you used in your answer or show a screenshot of the properties dialog box.

Common pitfall

Stretching an image by dragging a side handle instead of a corner handle, which distorts the image by changing its aspect ratio.

Worked example 12 marks

In a word processing document, insert an image named 'logo.png'. Position the image exactly 4cm from the top margin and 5cm from the left margin.

  1. 1

    Click 'Insert' > 'Picture' and select 'logo.png'.

  2. 2

    Right-click the image and choose 'Format Picture' or a similar option like 'Size and Position'.

  3. 3

    Navigate to the 'Position' tab.

  4. 4

    Under 'Horizontal', set the absolute position to 5cm from the 'Page' or 'Left Margin'.

  5. 5

    Under 'Vertical', set the absolute position to 4cm from the 'Page' or 'Top Margin'.

  6. 6

    Click 'OK' to apply the changes.

Worked example 22 marks

An image is 10cm wide and 8cm high. Resize it so its height is 6cm, while maintaining the aspect ratio. What is the new width?

  1. 1

    Right-click the image and choose 'Format Picture' > 'Size'.

  2. 2

    Ensure the 'Lock aspect ratio' checkbox is ticked.

  3. 3

    In the 'Height' input box, change the value from 8cm to 6cm.

  4. 4

    The width will automatically update to maintain the ratio. The original ratio is 10:8 or 1.25. The new width will be 6cm * 1.25 = 7.5cm.

  5. 5

    The new dimensions are 7.5cm (width) x 6cm (height).

Recap

  • Images can be positioned precisely using coordinate values from the page margins.
  • Resizing changes the dimensions of an image.
  • Always drag corner handles to resize an image and maintain its aspect ratio.
  • Dragging side handles will distort the image.
  • The 'Lock aspect ratio' option in formatting tools ensures no distortion occurs during resizing.

Quick check

  1. What is the function of the 'Lock aspect ratio' option when resizing an image?1 mark
  2. Which handles should you drag to resize an image without distorting it?1 mark

2. Cropping, Rotating, and Flipping

These are three common ways to transform an image. Cropping removes unwanted outer parts of an image to improve composition or focus on a specific area. Unlike resizing, it changes the image content. Rotating turns an image around a central point, either by a specific angle (e.g., 15 degrees) or in standard 90-degree increments. Flipping creates a mirror image. A horizontal flip swaps the left and right sides, while a vertical flip swaps the top and bottom.

Key term

Cropping: The process of removing unwanted outer areas of an image to improve its framing or composition.

Examiner insight

When asked to describe a process, clearly state the tools used (e.g., 'the Crop tool') and the actions taken (e.g., 'drag the handles inwards').

Common pitfall

Confusing cropping with resizing. Cropping removes parts of the image content, while resizing scales the entire image.

Worked example 13 marks

You have an image of a group of people, but you only want to show one person's face. Describe the steps to achieve this.

  1. 1

    Select the image.

  2. 2

    Find and select the 'Crop' tool, usually located in the 'Picture Format' tab.

  3. 3

    Black cropping handles will appear around the image.

  4. 4

    Drag the handles inwards to frame the desired person's face.

  5. 5

    The areas to be removed will appear greyed out.

  6. 6

    Click the 'Crop' button again or press 'Enter' to apply the crop. The unwanted parts of the image are now removed.

Worked example 22 marks

In your document, make a copy of an image. Flip the copy horizontally and then rotate it clockwise by 90 degrees.

  1. 1

    Select the original image and copy it (Ctrl+C).

  2. 2

    Paste the copy into the document (Ctrl+V).

  3. 3

    With the new copy selected, go to the 'Picture Format' tools.

  4. 4

    Find the 'Rotate' option and select 'Flip Horizontal'. The image is now a mirror image of the original.

  5. 5

    Go back to the 'Rotate' option and select 'Rotate Right 90°'. The image is now flipped and rotated.

Recap

  • Cropping removes unwanted outer portions of an image.
  • Resizing makes the entire image smaller or larger, while cropping changes its composition.
  • Rotating turns an image around a central point.
  • Flipping creates a mirror image, either horizontally or vertically.

Quick check

  1. What is the key difference between cropping and resizing an image?2 marks

3. Brightness, Contrast and Colour Depth

You can adjust an image's appearance to make it clearer or to create a specific mood. Brightness controls the overall lightness or darkness of an image. Increasing brightness makes every pixel lighter. Contrast is the difference between the light and dark areas. Increasing contrast makes whites whiter and blacks blacker, which can make an image look more 'punchy' but may cause loss of detail in very bright or dark areas. Colour Depth refers to the number of colours an image can display. It's measured in bits, where the number of colours is 2 to the power of the bit depth. A higher colour depth means more colours and a more realistic image, but a larger file size.

Number of colours = 2^(Colour Depth)

Key term

Colour Depth: The number of bits used to indicate the colour of a single pixel, which determines the total number of colours the image can contain.

Fun fact

A standard 24-bit JPEG image can display over 16.7 million different colours, which is more than the human eye can distinguish.

Worked example 14 marks

A photograph taken indoors without a flash appears too dark. Which two adjustments could you make to improve its visibility, and what would each do?

  1. 1

    Adjustment 1: Increase Brightness. This will make all pixels in the image lighter, making the overall scene more visible.

  2. 2

    Adjustment 2: Decrease Contrast. If the dark areas are completely black, decreasing the contrast might bring back some detail from the shadows, although increasing brightness is the primary solution for an image that is too dark overall.

  3. 3

    Alternatively, if the image is dark but also 'flat', increasing contrast after increasing brightness can help restore definition.

Worked example 22 marks

An image has a colour depth of 8-bit. How many different colours can it display?

  1. 1

    The formula for the number of colours is 2^(Colour Depth).

  2. 2

    In this case, the colour depth is 8 bits.

  3. 3

    Calculation: 2^8 = 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 = 256.

  4. 4

    The image can display 256 different colours.

Recap

  • Brightness adjusts the overall lightness or darkness of an image.
  • Contrast adjusts the difference between the light and dark parts of an image.
  • Colour depth determines the number of colours an image can contain.
  • A typical 24-bit image can display over 16.7 million colours (2^24).

Quick check

  1. What adjustment would you make to an image that looks 'washed out'?1 mark
  2. How many colours are in a 1-bit image?1 mark

4. Grouping and Layering Images

When working with multiple images or objects in a document, it's useful to manage them together. Grouping allows you to select multiple objects and treat them as a single unit. Once grouped, you can move, resize, or rotate all the objects together without changing their positions relative to each other. Layering refers to the stacking order of objects. Objects can be placed on top of or behind one another. You can use commands like 'Bring to Front', 'Send to Back', 'Bring Forward', and 'Send Backward' to control which objects are visible when they overlap.

Key term

Grouping: A function that allows multiple separate objects to be combined so they can be manipulated as a single object.

Examiner insight

Candidates who can successfully group multiple objects and then apply a transformation (like rotation) to the entire group demonstrate a higher level of skill.

Common pitfall

Forgetting to ungroup objects when you need to edit just one of them. Always remember to ungroup, make your change, and then regroup if necessary.

Worked example 13 marks

You have inserted a company logo and a text box with the company name. You want them to always stay together when moved. How do you achieve this?

  1. 1

    Select the first object (the company logo).

  2. 2

    Hold down the 'Shift' or 'Ctrl' key on your keyboard.

  3. 3

    While holding the key, click on the second object (the text box). Both objects should now be selected.

  4. 4

    Right-click on one of the selected objects.

  5. 5

    From the context menu, find the 'Group' option and select 'Group'.

  6. 6

    The two objects will now be treated as one and can be moved or resized together.

Worked example 23 marks

You have a large background image, a medium-sized photo, and a small caption text box. Arrange them so the background is at the very back, the photo is in the middle, and the caption is on top.

  1. 1

    Select the large background image.

  2. 2

    Right-click it and choose 'Send to Back'. This places it at the bottom layer.

  3. 3

    Select the small caption text box.

  4. 4

    Right-click it and choose 'Bring to Front'. This places it on the top layer.

  5. 5

    The medium-sized photo will now automatically be in the middle layer, between the other two objects.

Recap

  • Grouping combines multiple objects into a single unit.
  • Grouped objects can be moved, resized, and rotated together.
  • Layering controls the front-to-back stacking order of overlapping objects.
  • Use 'Bring to Front' and 'Send to Back' to manage layers.

Quick check

  1. What is the purpose of grouping two images?1 mark
  2. Which command would you use to place an image behind all other objects?1 mark

5. Reducing Image File Size

Large image files can slow down websites, take up too much storage space, and be difficult to email. There are two main ways to reduce an image's file size, both of which involve a trade-off with quality. 1. Reducing Resolution: This means reducing the number of pixels in the image (e.g., changing from 4000x3000 pixels to 800x600 pixels). This is very effective at reducing file size but makes the image physically smaller and can result in a loss of sharp detail, making it look blurry if enlarged. 2. Reducing Colour Depth: This means reducing the number of colours the image uses (e.g., from 24-bit colour to 8-bit colour). This can significantly reduce file size but may result in banding or posterization in photographs, where smooth gradients of colour become visible steps. This method is more suitable for simple graphics like logos than for detailed photos.

Image File Size ≈ (Resolution in pixels) × (Colour Depth in bits)

Key term

Resolution: The number of pixels in an image, typically expressed as width × height (e.g., 1920x1080).

Examiner insight

For analysis questions, examiners want you to discuss the trade-offs. A good answer will state that reducing resolution is best for web images, while reducing colour depth is suitable for simple graphics but not for photos.

Worked example 16 marks

Analyse the methods that can be used for reducing the file size of an image and suggest situations where each would be the most appropriate method.

  1. 1

    Method 1: Reducing Resolution. This involves decreasing the number of pixels (width and height). It significantly reduces file size. The impact is a loss of detail and the image cannot be enlarged without appearing pixelated. This method is most appropriate for images intended for web use or email, where screen display size is limited and fast loading is important.

  2. 2

    Method 2: Reducing Colour Depth. This involves lowering the number of bits per pixel, which reduces the number of available colours. This also reduces file size. The impact is a loss of colour fidelity; smooth colour gradients may become blocky (posterization). This method is most appropriate for simple graphics, icons, or logos that use only a few solid colours. It is not suitable for photographic images.

  3. 3

    Conclusion: For a photograph to be displayed on a website, reducing the resolution is the best primary method. For a company logo with three solid colours, reducing the colour depth would be very effective and have little visible impact.

Recap

  • Image file size can be reduced by lowering resolution or lowering colour depth.
  • Reducing resolution decreases the number of pixels in the image.
  • Reducing colour depth decreases the number of colours the image can display.
  • Both methods of file size reduction result in a loss of image quality.
  • The best method depends on the image type and its intended use.

Quick check

  1. Name two ways to reduce the file size of a digital image.2 marks
  2. Which method of file size reduction is generally unsuitable for a colour photograph of a sunset?1 mark

End-of-chapter exercise

Test yourself on the whole chapter. Work through these before moving on.

  1. With reference to manipulating images, define the terms 'crop' and 'flip'.2 marks
  2. Describe the steps to insert an image into a document and resize it to a height of 5cm while maintaining its aspect ratio.3 marks
  3. You have placed an image on a page. How would you create a copy of it, and then place the copy so it is a mirror image of the original?3 marks
  4. Explain the difference between resizing an image and cropping an image. Give an example of when you would use each technique.4 marks
  5. You have three images: a large background (A), a medium portrait (B), and a small logo (C). Describe how to layer them so that the background is at the back, the portrait is in front of it, and the logo is on top of everything.3 marks
  6. You have created a diagram using three separate shapes. Explain how you would group them and then rotate the entire group by 45 degrees.3 marks
  7. Explain, with examples, how reducing image resolution and reducing colour depth can lower the file size of an image. You must also describe the negative impact of each method.6 marks
  8. An image has a colour depth of 16 bits. Calculate the maximum number of colours it can display. Show your working.2 marks
  9. A photograph of a landscape on a cloudy day looks very 'flat' and dull. State one adjustment you could make to improve it and explain why this would help.2 marks
  10. Insert an image into a document. Position it 10cm from the top of the page and aligned to the right margin. Set the text wrapping to 'Tight' so that document text flows around the shape of the image.4 marks

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