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ICDL Image Editing study materials
ICDL Image Editing study resources

ICDL Image Editing (ICDL) practice questions

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Question 1Imaging concepts

What is a pixel in a bitmap image?

  1. A measurement of printer output density
  2. The smallest addressable unit of a bitmap image Correct answer.
  3. A closed shape drawn from mathematical coordinates
  4. A tag that records camera settings

Explanation

A bitmap (raster) image is a grid of picture elements, and each pixel holds one colour value for that position. Shapes defined by coordinates belong to vector graphics, and output density is a printing measure rather than a picture element.

Question 2Imaging concepts

Which file type stores an image as scalable mathematical descriptions rather than a grid of pixels?

  1. BMP
  2. PNG
  3. JPEG
  4. SVG Correct answer.

Explanation

SVG is a vector format that records shapes as paths, curves and coordinates, so it can be scaled without loss of sharpness. JPEG, BMP and PNG all store a fixed grid of pixels.

Question 3Imaging concepts

Which statement describes JPEG compression?

  1. It permanently discards some data to reduce file size Correct answer.
  2. It stores every pixel exactly as captured with no data loss
  3. It is limited to a palette of 256 colours
  4. It supports animation and full alpha transparency

Explanation

JPEG is a lossy format: data is discarded during encoding and cannot be restored when the file is reopened. Lossless formats such as PNG or TIFF keep every pixel value intact, and palette limits and animation apply to GIF.

Question 4Imaging concepts

In an RGB image, which three colours are combined additively to create other colours?

  1. Cyan, magenta and yellow
  2. Red, green and blue Correct answer.
  3. Hue, saturation and brightness
  4. Red, yellow and blue

Explanation

RGB is an additive model: red, green and blue light are added together, and combining all three at full strength produces white. Cyan, magenta and yellow form the subtractive model used for inks.

Question 5Imaging concepts

What does a resolution of 300 ppi describe?

  1. The number of inches wide the printed page will be
  2. The number of colours each pixel can display
  3. The number of bits used per colour channel
  4. The number of image pixels printed per inch Correct answer.

Explanation

Pixels per inch expresses how densely image pixels are packed when the picture is output, which controls how large the print appears and how sharp it looks. Colour depth and physical page size are separate attributes.

Question 6Imaging concepts

Which feature most distinguishes PNG from JPEG for web graphics?

  1. Smaller file sizes for photographic content
  2. Lossless compression and transparency Correct answer.
  3. Support for multiple animated frames
  4. Native storage of raw camera sensor data

Explanation

PNG compresses without discarding data and can store an alpha channel, so it suits logos, text and graphics needing transparency. JPEG gives smaller photographic files but has no transparency, and raw sensor data is stored in proprietary raw formats.

Question 7Imaging concepts

An image is 1920 pixels wide and 1080 pixels high. What is its aspect ratio?

  1. 1:1
  2. 3:2
  3. 4:3
  4. 16:9 Correct answer.

Explanation

Aspect ratio is width divided by height: 1920 ÷ 1080 reduces to 16:9. A 4:3 image at the same width would be 1440 pixels high, and a 1:1 image would be square.

Question 8Imaging concepts

Which operation removes pixels from the edges of an image without changing the size of the remaining pixels?

  1. Scaling
  2. Cropping Correct answer.
  3. Rotating
  4. Resampling

Explanation

Cropping discards the outer areas of an image and keeps the remaining pixels at their original size and resolution. Resampling and scaling recalculate pixel values and therefore change how each pixel is represented.

Question 9Imaging concepts

In an indexed colour image, what do the stored pixel values refer to?

  1. Layers within a document
  2. Coordinates of a vector path
  3. Channels of a CMYK file
  4. Entries in a fixed colour table Correct answer.

Explanation

Indexed colour stores a small number, such as 0–255, in each pixel and looks up the actual colour in a palette table. This keeps files small but limits the image to the number of colours the table holds.

Question 10Imaging concepts

Why is CMYK rather than RGB normally used to prepare images for commercial printing?

  1. CMYK models the subtractive inks used by printers Correct answer.
  2. CMYK files are always smaller than RGB files
  3. CMYK images can store transparency in four channels
  4. CMYK supports a wider range of colours than RGB

Explanation

Printers lay down cyan, magenta, yellow and black inks, which subtract light from white paper, so CMYK reflects the printing process. RGB describes emitted light and covers a different, generally larger, portion of the visible spectrum.

Question 11Imaging concepts

Which statement about enlarging a raster image with interpolation is accurate?

  1. It recovers fine detail that was lost when the image was captured
  2. It adds invented pixels, so edges appear softer Correct answer.
  3. It keeps the file size unchanged because no pixels are added
  4. It converts the image into a vector graphic that scales without loss

Explanation

Interpolation estimates new pixel values from neighbouring pixels, so no original detail is created and the result looks softer. True detail can only come from a higher-resolution original or a vector source.

Question 12Imaging concepts

What is the main reason GIF is a poor choice for full-colour photographs?

  1. It is limited to a palette of 256 colours Correct answer.
  2. It always uses lossy compression that blurs detail
  3. It cannot be displayed in web browsers
  4. It stores no information about image size

Explanation

GIF is an indexed format capped at 256 colours, so continuous photographic tones become banded or dithered. It also uses lossless compression, so the colour limit rather than compression quality is the main drawback.

Question 13Imaging concepts

A logo must stay sharp on business cards and on a large billboard. Which file should be used?

  1. A GIF with an indexed palette
  2. A vector file such as SVG Correct answer.
  3. A JPEG at 300 ppi
  4. A bitmap saved at 72 ppi

Explanation

Vector artwork is defined by paths and coordinates, so it can be output at any size with no loss of sharpness. Bitmap files are tied to a fixed pixel grid and become blocky when scaled far beyond their native size.

Question 14Imaging concepts

A camera produces images of 4000 × 3000 pixels. How many megapixels is that?

  1. 12 Correct answer.
  2. 16
  3. 7
  4. 24

Explanation

Multiply the two dimensions to get the total pixel count: 4000 × 3000 = 12,000,000 pixels, which is 12 megapixels. One megapixel equals one million pixels.

Question 15Imaging concepts

What does the alpha channel of an image control?

  1. The amount of sharpening applied to edges
  2. The total number of colours in the palette
  3. The transparency level of each pixel Correct answer.
  4. The colour temperature of the white point

Explanation

An alpha channel stores an opacity value for every pixel, allowing an image to blend with whatever lies behind it. Colour information is held separately in the RGB or CMYK channels.

Question 16Imaging concepts

In HSL colour adjustment, what does the saturation value describe?

  1. The opacity of the layer the colour sits on
  2. How pure or greyish the colour appears Correct answer.
  3. The position of the colour on the colour wheel
  4. How light or dark the colour is

Explanation

Saturation measures the intensity of a colour, ranging from fully grey at zero to vivid at maximum. Hue gives the position on the colour wheel and lightness gives how light or dark the colour is.

Question 17Imaging concepts

What is the purpose of anti-aliasing when rendering text or edges?

  1. To soften jagged edges by blending boundary pixels Correct answer.
  2. To convert colour images into greyscale
  3. To increase the file's bit depth automatically
  4. To compress the image without losing detail

Explanation

Anti-aliasing fills boundary pixels with intermediate colours so that diagonal and curved edges appear smooth at normal viewing size. It changes appearance only and does not change colour depth or compression.

Question 18Imaging concepts

An editor saves a photo with a very low JPEG quality setting. What is the likely result?

  1. The colour mode is converted to CMYK automatically
  2. The image becomes lossless and larger in file size
  3. Visible blocky artefacts appear around detailed areas Correct answer.
  4. The image gains an alpha channel for transparency

Explanation

Lower JPEG quality discards more information, and the 8 × 8 block structure of the encoder becomes visible as blocky artefacts and colour smearing. The file shrinks, and the change is permanent once saved.

Question 19Imaging concepts

A 1200 × 900 pixel image is printed at 300 ppi. What size will the print be?

  1. 12 × 9 inches
  2. 8 × 6 inches
  3. 4 × 3 inches Correct answer.
  4. 2 × 1.5 inches

Explanation

Divide each pixel dimension by the output density: 1200 ÷ 300 = 4 inches wide and 900 ÷ 300 = 3 inches high. Lower ppi values would produce a larger print from the same pixels.

Question 20Imaging concepts

What is stored in the EXIF data of a digital photograph?

  1. The colour profile only, with no other fields
  2. The compressed pixel values of each colour channel
  3. A second copy of the image used for backup
  4. Camera model, date and exposure settings Correct answer.

Explanation

EXIF is metadata written alongside the image data and records capture details such as camera model, date and time, aperture, shutter speed and ISO. It does not contain pixel values or a backup copy.

Question 21Imaging concepts

A greyscale image has a bit depth of 4. How many distinct shades can it contain?

  1. 64
  2. 256
  3. 16 Correct answer.
  4. 4

Explanation

Bit depth gives 2 raised to the power of the number of bits, so 2⁴ = 16 possible values. Each additional bit doubles the number of shades available.

Question 22Imaging concepts

Two monitors are both 8-bit RGB, yet one reproduces noticeably more vivid greens. What best explains this?

  1. One monitor applies lossy compression to the signal
  2. The monitors have different colour gamuts Correct answer.
  3. One monitor stores images at a larger pixel count
  4. One monitor uses a higher bit depth than the other

Explanation

Gamut is the range of colours a device can actually reproduce, and it varies between panels even when the bit depth is identical. Bit depth limits the number of steps within a gamut, but the gamut itself determines which colours are reachable.

Question 23Imaging concepts

A vector logo is exported to a 1000 × 1000 pixel bitmap for screen use. What determines whether its curves look smooth?

  1. The size of the palette used by the bitmap
  2. The compression level chosen for the output file
  3. The number of anchor points defined in the vector path
  4. The export resolution and anti-aliasing applied Correct answer.

Explanation

Once rasterised, the shape is sampled onto a pixel grid, so smoothness depends on how many pixels describe the curve and whether boundary pixels are blended. Anchor points describe the source shape, not the rendered quality.

Question 24Imaging concepts

A photograph's histogram shows a tall spike pressed against the far right edge. What does this indicate?

  1. The image has very low contrast overall
  2. Highlight detail has been clipped and is lost Correct answer.
  3. The image is underexposed and lacks shadow detail
  4. The image contains no pure white tones

Explanation

The right edge of a histogram represents the brightest tones, so a spike there means many pixels have reached maximum value and their detail cannot be recovered. Clipping at the left edge would indicate lost shadow detail instead.

Question 25Imaging concepts

What advantage does a progressively encoded web image offer over a baseline one?

  1. The image can be edited without recompression
  2. The colours are stored with greater precision
  3. A blurry preview appears during download Correct answer.
  4. The file is always smaller in byte size

Explanation

Progressive (interlaced) encoding arranges the data so a coarse version of the whole image displays first and sharpens as more data arrives. It does not change the colour depth or guarantee a smaller file.

Question 26Imaging concepts

Which description best matches a raster image?

  1. A list of colour codes saved as plain text
  2. A stack of linked editing layers
  3. A grid of pixels holding colour values Correct answer.
  4. A set of mathematical paths and shapes

Explanation

Raster (bitmap) images are built from a rectangular grid of pixels, and each pixel stores a colour value. Because the picture is defined pixel by pixel, its appearance is tied to a fixed pixel count. Paths and shapes describe vector graphics instead.

Question 27Imaging concepts

In an additive colour model such as RGB, which colour results from mixing red light and green light at full strength?

  1. Magenta
  2. Cyan
  3. Yellow Correct answer.
  4. White

Explanation

Adding red and green light produces yellow in an additive model, because the two sets of wavelengths together stimulate the eye's red and green receptors. Mixing all three primaries gives white, while cyan, magenta and yellow arise from subtractive mixing of inks or from other pairings.

Question 28Imaging concepts

What does the pixels-per-inch value of an image file describe?

  1. The physical width of the paper the image is printed on
  2. How many printer dots are laid down along one inch
  3. How many image pixels are placed in one inch of output Correct answer.
  4. How many separate colours the output device can reproduce

Explanation

Pixels per inch expresses how densely the image's own pixels are packed when it is placed at a given physical size. It is a property of the image-to-output relationship rather than of the printer's hardware. Printer dots per inch describes the output device instead.

Question 29Imaging concepts

What does the colour gamut of a device describe?

  1. The number of bits used for each colour channel
  2. The speed at which colours are converted
  3. The maximum screen brightness the device reaches
  4. The range of colours a device can reproduce Correct answer.

Explanation

A gamut is the boundary of colours a particular device, ink set or colour space is able to represent. Different devices have different gamuts, which is why colours can shift when files move between them. Bit depth governs how many steps are available inside that range, not its extent.

Question 30Imaging concepts

Why would an editor retouch a photograph at 16 bits per channel rather than 8?

  1. It allows a wider choice of file formats to be saved
  2. It makes the final file smaller for web delivery
  3. It gives more levels to darker tones where steps are visible Correct answer.
  4. It increases the pixel dimensions of the image

Explanation

Higher bit depth provides many more discrete levels per channel, so smooth tonal transitions survive repeated adjustments without visible banding. The extra data also protects shadow and highlight detail during heavy edits. It does not change pixel count or make files smaller.

Question 31Imaging concepts

What is the role of an embedded ICC profile in an image file?

  1. It logs where and when the image was edited
  2. It compresses the image data to reduce file size
  3. It defines how the image's colour values map to device colours Correct answer.
  4. It records the camera settings used for the shot

Explanation

An ICC profile is a colour-management description of how numeric colour values should be interpreted so that colours appear consistently across devices. Without it, an application can only guess the intended colour space. Capture settings and edit history belong to metadata fields such as EXIF.

Question 32Imaging concepts

An image's histogram shows all tones gathered in the middle, with no pixels near either end. What does this indicate?

  1. The image is very high in contrast
  2. The image has low contrast with unused tonal range Correct answer.
  3. The image is mostly pure black
  4. The image has been converted to greyscale

Explanation

A histogram that clusters in the middle means no pixels sit at the darkest or brightest extremes, so the tonal range is compressed and the picture looks flat. Extending the tones toward both ends would raise contrast. A greyscale conversion affects colour data, not the shape of the tonal spread.

Question 33Imaging concepts

Photographs taken indoors under tungsten lamps look strongly orange. Which correction addresses the cause?

  1. Adjust the white balance to a warmer setting
  2. Reduce the saturation of the whole image
  3. Adjust the white balance to neutralise the colour cast Correct answer.
  4. Convert the image to greyscale

Explanation

A colour cast from a light source with an unusual colour temperature is corrected by setting white balance so that neutral objects render as neutral. The adjustment counteracts the warm bias of the lighting rather than pushing further in the same direction. Global saturation or greyscale changes alter the picture but do not fix the underlying cast.

Question 34Imaging concepts

Which statement about lossless compression is accurate?

  1. It always produces smaller files than lossy methods
  2. It can only be applied to vector graphics
  3. It preserves every original pixel value exactly Correct answer.
  4. It removes fine detail the eye is unlikely to notice

Explanation

Lossless compression exploits redundancy in the data so the file can be rebuilt to exactly the original values when decompressed. Nothing is discarded, so repeated open-and-save cycles cause no cumulative degradation. Lossy methods achieve smaller files precisely because they throw information away.

Question 35Imaging concepts

Which resampling method best preserves the hard edges of pixel art when it is enlarged?

  1. Bicubic interpolation
  2. Bilinear interpolation
  3. Nearest neighbour Correct answer.
  4. Lanczos resampling

Explanation

Nearest neighbour copies the value of the closest source pixel to each new pixel, so sharp boundaries stay sharp and the blocky character of pixel art is retained. The other methods average neighbouring pixels, which introduces softness or ringing along edges. That smoothing is welcome for photographs but not for pixel art.

Question 36Imaging concepts

Why is dithering applied when an image is reduced to a small palette?

  1. To remove noise from a scanned photograph
  2. To raise the file's bit depth automatically
  3. To mix available colours so gradients look smoother Correct answer.
  4. To sharpen edges before printing

Explanation

With few colours available, smooth transitions would otherwise show as visible bands. Dithering scatters pixels of the available colours in patterns so the eye blends them into apparent intermediate tones. It works within the existing palette and cannot increase the number of stored colours.

Question 37Imaging concepts

A vector drawing is exported as a 400 x 400 pixel bitmap. What determines whether its curves look smooth?

  1. The colour mode of the source document
  2. The number of anchor points in the original path
  3. The resolution chosen for the export Correct answer.
  4. The amount of metadata stored in the file

Explanation

Once a vector is rasterised, its smoothness depends on how many pixels are available to describe the curves, which is set by the export resolution. A low pixel count forces curves into visible stair steps. The anchor count and colour mode affect other qualities but cannot add the missing pixels.

Question 38Imaging concepts

A vivid green from an RGB photograph is prepared for a CMYK brochure. What typically happens to colours that fall outside the CMYK gamut?

  1. They are converted automatically into a spot colour
  2. They are preserved exactly because CMYK covers all RGB colours
  3. They are saved in the alpha channel for later recovery
  4. They are shifted to the nearest reproducible colour, often duller Correct answer.

Explanation

Ink-based CMYK reproduction covers a smaller range of colours than emissive RGB, so highly saturated colours cannot be matched exactly. Colour management maps them to the closest achievable values, and the result usually looks less vivid. The original values are not retained for later recovery in a standard conversion.

Question 39Imaging concepts

Why can some image encoders store colour detail at a lower resolution than brightness detail with little visible loss?

  1. Brightness values can be rebuilt from the file's metadata
  2. Colour channels are always compressed without any loss
  3. Colour detail is always held in a separate alpha channel
  4. Human vision resolves brightness detail better than colour detail Correct answer.

Explanation

The eye contains far more sensors tuned to luminance than to fine chromatic differences, so it detects changes in brightness more readily than changes in hue. Reducing colour resolution therefore removes data the viewer is unlikely to miss. Luminance must be kept at full resolution because losses there are obvious.

Question 40Imaging concepts

Why is gamma encoding applied when an 8-bit image is stored?

  1. It gives more levels to darker tones where steps are visible Correct answer.
  2. It doubles the file's effective colour depth with no extra data
  3. It converts the image from RGB to CMYK for printing
  4. It removes compression artefacts left by a previous save

Explanation

Human perception is far more sensitive to differences in dark tones than in bright ones, whereas 8-bit storage allocates levels in equal steps. Gamma encoding redistributes the available levels so that shadows receive finer gradation. It does not add bit depth, alter colour space, or repair earlier compression.

Question 41Image capture and acquisition

In image work, what does the abbreviation DPI refer to?

  1. Data pixels per image
  2. Digital picture index
  3. Display proportions indicator
  4. Dots per inch Correct answer.

Explanation

DPI stands for dots per inch and describes how many ink dots a printer can place within one inch. It is a measure of output device resolution, not of the pixels stored in an image file.

Question 42Image capture and acquisition

In digital photography, what is a RAW file?

  1. A screenshot saved by the camera software
  2. A vector drawing exported from a camera
  3. Unprocessed sensor data from the camera Correct answer.
  4. A compressed image ready for web use

Explanation

A RAW file stores the unprocessed data captured by the sensor, with little or no in-camera processing applied. This gives more flexibility when editing exposure and colour, but the file normally has to be converted before everyday use.

Question 43Image capture and acquisition

A flatbed scanner is used mainly to:

  1. Turn printed images into digital files Correct answer.
  2. Record video clips in low light conditions
  3. Print digital photographs onto glossy paper
  4. Reduce file sizes for email attachments

Explanation

A scanner shines light onto a flat original and records the reflected light as digital pixel values. It converts analogue material such as prints or documents into an image file.

Question 44Image capture and acquisition

What does the pixel dimension 3000 × 2000 of an image describe?

  1. The compression ratio used when saving
  2. The physical size of the print in inches
  3. The number of colours the image can store
  4. The width and height in pixels Correct answer.

Explanation

Pixel dimensions give the number of pixels across the width and the height of the image grid. Multiplying them gives the total pixel count, here six million pixels.

Question 45Image capture and acquisition

An image of 4000 × 3000 pixels is approximately how many megapixels?

  1. 1.2 megapixels
  2. 12 megapixels Correct answer.
  3. 7 megapixels
  4. 120 megapixels

Explanation

Multiplying 4000 by 3000 gives 12,000,000 pixels, and one megapixel equals one million pixels. The image is therefore about 12 megapixels.

Question 46Image capture and acquisition

Which storage medium is most commonly used inside a consumer digital camera?

  1. Floppy disk
  2. SD memory card Correct answer.
  3. CD-ROM disc
  4. Magnetic tape

Explanation

Consumer cameras normally record images to removable flash memory, most often an SD card. These cards are small, rewritable and can be read by a computer through a card reader.

Question 47Image capture and acquisition

What is the result of taking a screenshot?

  1. A printed copy of the open document
  2. A backup of the hard disk contents
  3. A text file listing open windows
  4. An image of the current screen Correct answer.

Explanation

A screenshot captures the pixels currently displayed on the screen and stores them as a raster image. It records exactly what is visible, including windows and interface elements.

Question 48Image capture and acquisition

An image with an aspect ratio of 4:3 means that:

  1. It stores four colours and three tones
  2. It contains four million pixels in total
  3. Width is 4 units for every 3 of height Correct answer.
  4. It is four times sharper than a 3:2 image

Explanation

Aspect ratio compares the width of an image with its height. At 4:3, every four units of width correspond to three units of height, whatever the actual pixel count.

Question 49Image capture and acquisition

What is the role of a TWAIN driver?

  1. Converting raster images into vectors
  2. Linking software to a scanner or camera Correct answer.
  3. Compressing images before they are saved
  4. Correcting colour balance in a photo

Explanation

TWAIN is a standard interface that lets image-editing software communicate with a scanner or camera. The driver passes the acquired image from the device into the application.

Question 50Image capture and acquisition

What kind of information is stored in EXIF metadata?

  1. Capture settings such as shutter speed and ISO Correct answer.
  2. The number of layers in the image file
  3. Licence terms of the image editing software
  4. The printer colour profile chosen for output

Explanation

EXIF data is written by the camera at the moment of capture and records technical details such as exposure time, aperture, ISO and date. It can also include orientation and GPS information.