A pixel is the smallest element of a bitmap image , stored as a binary code that is unique to the colour in that pixel.

Define image resolution .

Image resolution is the total amount of pixels that make up a bitmap image , calculated by multiplying the height and width of the image in pixels.

What does screen resolution refer to?

The total amount of pixels horizontally in a display .

Define pixel density .

Pixel density is the number of pixels per square inch (PPI) of a display.

Why can a smartphone screen be viewed close up without pixelation?

Smartphones have very high screen resolutions in much smaller screens , giving a much higher PPI , often over 300 PPI .

Define colour depth .

Colour depth is the number of bits stored per pixel in a bitmap image.

What formula gives the number of colours available from a given colour depth?

Number of colours = 2ⁿ , where n is the number of bits .

How many colours can a 1-bit and a 2-bit image represent?

A 1-bit image can represent 2 colours and a 2-bit image can represent 4 colours .

How many colours can an 8-bit and a 24-bit image represent?

An 8-bit image can represent 256 colours , and a 24-bit true colour image can represent 16,777,216 colours .

The size of a bitmap file is estimated as resolution multiplied by .

The size of a bitmap file is estimated as resolution multiplied by colour depth .

What is the file size in bytes of a bitmap with a resolution of 250,000 and a colour depth of 24 bits?

250,000 × 24 = 6,000,000 bits , which divided by 8 gives 750,000 bytes .

A bitmap section is 10 pixels wide and 5 pixels high with up to 256 colours. What is its estimated file size in bytes?

256 colours needs 8 bits per pixel; 10 × 5 = 50 pixels, and 50 × 8 = 400 bits, so the file is 50 bytes .

Name four things stored in a bitmap file header.

The file type , the file size , the image resolution , the colour depth , and any type of compression used.

Why does increasing the resolution increase the file size?

The higher the resolution, the more pixels are in the image, so more bits are stored .

Why does increasing the colour depth increase the file size?

The higher the colour depth, the more bits per pixel are stored.

True or False? A higher quality bitmap image can be produced with no cost to file size.

False. As resolution and colour depth increase, the file size becomes bigger , so striking a balance between quality and file size is always a consideration; compression can help reduce the size.

Define vector graphic .

A vector graphic is an image created from mathematical equations and points , where only the mathematics used to create the image are stored.

What data is stored to create a circle in a vector graphic?

The centre point as x and y coordinates, and the radius .

A vector graphic contains a list, which is included in the file header.

A vector graphic contains a drawing list, which is included in the file header.

Name the three things a typical drawing list contains.

The commands used to create each object , the attributes that define the properties of each object , and the relative position of each object .

Why does scaling up a vector graphic not cause a loss of quality?

The dimensions of the image are not defined , so the mathematics are simply recalculated at the new size.

Give a situation where a vector graphic is the right choice.

Where the same image will be made bigger and smaller and a loss of quality is unacceptable , such as a logo used on both a pencil and a billboard.

What is a bitmap image made from, compared with a vector image?

A bitmap is made from pixels , which are tiny coloured squares, while a vector is made from shapes and lines defined using maths .

How do bitmap and vector file sizes compare?

A bitmap is larger , depending on its resolution, while a vector is smaller because it uses formulas rather than pixels.

What is each format best for?

Bitmaps are best for photographs and detailed images , while vectors are best for logos, icons and text graphics .

Name three questions to ask when choosing between a bitmap and a vector image.

Does the image need to be resized ? Does it need to be drawn to scale ? Does it need to look real ?

True or False? A bitmap image can be resized without losing quality.

False. A bitmap loses quality when resized and pixelates; it is the vector image that can be resized without losing quality.

Why must analogue sound be converted before a computer can use it?

Computers represent all data in binary , so sound waves that begin as analogue must be converted into a digital form .

Converting a sound wave into binary is called to digital conversion.

Converting a sound wave into binary is called analogue to digital conversion.

Sampling is measuring the loudness, or amplitude, of the analogue sound wave at a point in time .

What does the amplitude of a sound wave represent?

The loudness — the higher the amplitude, the louder the sound.

What happens to each sample once it is measured?

Each sample generates a value which is represented in binary and stored on secondary storage.

Define sampling rate .

The sampling rate is the number of samples taken per second of the analogue wave, measured in Hertz (Hz) .

How many samples of a sound wave does 1 Hertz represent?

1 Hertz is equal to 1 sample of the sound wave.

Define sampling resolution .

Sampling resolution is the number of bits used to represent each sound sample .

Which property of a bitmap image is sampling resolution equivalent to?

The bit depth of a bitmap image — they measure the same thing in different contexts.

What are the sampling rate and sampling resolution of a typical audio CD?

A sampling rate of 44.1 kHz , which is 44,100 samples per second, and a sampling resolution of 16 bits , recorded in stereo.

What effect does a higher sampling rate have on quality and file size?

A higher sampling rate captures more detail and better sound quality , but stores more data, giving a larger file size .

What effect does a higher sampling resolution have on quality and file size?

A higher sampling resolution gives a bigger range and better sound quality , but stores more data per sample, giving a larger file size .

True or False? Raising the sampling rate improves sound quality with no cost to the file.

False. A higher sampling rate means more data is stored , giving a larger file size .

A LevelComputer ScienceCambridge (CIE)Flashcards1. Information representationMultimedia

Multimedia (Cambridge (CIE) A Level Computer Science): Flashcards

Exam code: 9618

1/41

0Still learning

Know0

FrontBitmap Images
Define pixel.

Was this flashcard helpful?

Cards in this collection (41)

Define pixel.
A pixel is the smallest element of a bitmap image, stored as a binary code that is unique to the colour in that pixel.
Define image resolution.
Image resolution is the total amount of pixels that make up a bitmap image, calculated by multiplying the height and width of the image in pixels.
What does screen resolution refer to?
The total amount of pixels horizontally in a display.
Define pixel density.
Pixel density is the number of pixels per square inch (PPI) of a display.
Why can a smartphone screen be viewed close up without pixelation?
Smartphones have very high screen resolutions in much smaller screens, giving a much higher PPI, often over 300 PPI.
Define colour depth.
Colour depth is the number of bits stored per pixel in a bitmap image.
What formula gives the number of colours available from a given colour depth?
Number of colours = 2ⁿ, where n is the number of bits.
How many colours can a 1-bit and a 2-bit image represent?
A 1-bit image can represent 2 colours and a 2-bit image can represent 4 colours.
How many colours can an 8-bit and a 24-bit image represent?
An 8-bit image can represent 256 colours, and a 24-bit true colour image can represent 16,777,216 colours.
The size of a bitmap file is estimated as resolution multiplied by .
The size of a bitmap file is estimated as resolution multiplied by colour depth.
What is the file size in bytes of a bitmap with a resolution of 250,000 and a colour depth of 24 bits?
250,000 × 24 = 6,000,000 bits, which divided by 8 gives 750,000 bytes.
A bitmap section is 10 pixels wide and 5 pixels high with up to 256 colours. What is its estimated file size in bytes?
256 colours needs 8 bits per pixel; 10 × 5 = 50 pixels, and 50 × 8 = 400 bits, so the file is 50 bytes.
Name four things stored in a bitmap file header.
The file type, the file size, the image resolution, the colour depth, and any type of compression used.
Why does increasing the resolution increase the file size?
The higher the resolution, the more pixels are in the image, so more bits are stored.
Why does increasing the colour depth increase the file size?
The higher the colour depth, the more bits per pixel are stored.
True or False?
A higher quality bitmap image can be produced with no cost to file size.
False.
As resolution and colour depth increase, the file size becomes bigger, so striking a balance between quality and file size is always a consideration; compression can help reduce the size.
Define vector graphic.
A vector graphic is an image created from mathematical equations and points, where only the mathematics used to create the image are stored.
What data is stored to create a circle in a vector graphic?
The centre point as x and y coordinates, and the radius.
Give two typical examples of a vector image.
Logos and clipart.
A vector graphic contains a list, which is included in the file header.
A vector graphic contains a drawing list, which is included in the file header.
Name the three things a typical drawing list contains.
The commands used to create each object, the attributes that define the properties of each object, and the relative position of each object.
Why does scaling up a vector graphic not cause a loss of quality?
The dimensions of the image are not defined, so the mathematics are simply recalculated at the new size.
Give a situation where a vector graphic is the right choice.
Where the same image will be made bigger and smaller and a loss of quality is unacceptable, such as a logo used on both a pencil and a billboard.
What is a bitmap image made from, compared with a vector image?
A bitmap is made from pixels, which are tiny coloured squares, while a vector is made from shapes and lines defined using maths.
How do bitmap and vector file sizes compare?
A bitmap is larger, depending on its resolution, while a vector is smaller because it uses formulas rather than pixels.
What is each format best for?
Bitmaps are best for photographs and detailed images, while vectors are best for logos, icons and text graphics.
Name three questions to ask when choosing between a bitmap and a vector image.
Does the image need to be resized? Does it need to be drawn to scale? Does it need to look real?
True or False?
A bitmap image can be resized without losing quality.
False.
A bitmap loses quality when resized and pixelates; it is the vector image that can be resized without losing quality.
Why must analogue sound be converted before a computer can use it?
Computers represent all data in binary, so sound waves that begin as analogue must be converted into a digital form.
Converting a sound wave into binary is called to digital conversion.
Converting a sound wave into binary is called analogue to digital conversion.
Define sampling.
Sampling is measuring the loudness, or amplitude, of the analogue sound wave at a point in time.
What does the amplitude of a sound wave represent?
The loudness — the higher the amplitude, the louder the sound.
What happens to each sample once it is measured?
Each sample generates a value which is represented in binary and stored on secondary storage.
Define sampling rate.
The sampling rate is the number of samples taken per second of the analogue wave, measured in Hertz (Hz).
How many samples of a sound wave does 1 Hertz represent?
1 Hertz is equal to 1 sample of the sound wave.
Define sampling resolution.
Sampling resolution is the number of bits used to represent each sound sample.
Which property of a bitmap image is sampling resolution equivalent to?
The bit depth of a bitmap image — they measure the same thing in different contexts.
What are the sampling rate and sampling resolution of a typical audio CD?
A sampling rate of 44.1 kHz, which is 44,100 samples per second, and a sampling resolution of 16 bits, recorded in stereo.
What effect does a higher sampling rate have on quality and file size?
A higher sampling rate captures more detail and better sound quality, but stores more data, giving a larger file size.
What effect does a higher sampling resolution have on quality and file size?
A higher sampling resolution gives a bigger range and better sound quality, but stores more data per sample, giving a larger file size.
True or False?
Raising the sampling rate improves sound quality with no cost to the file.
False.
A higher sampling rate means more data is stored, giving a larger file size.

Sign up to unlock flashcards

By signing up you agree to our Terms and Privacy Policy

Previous:Data RepresentationNext:Compression