Topic 7 - Data representation (Images & Sound)

Why is hexadecimal code used in computing?

to simplify binary representation as it is easier to write numbers as hex than binary

Do computers use hexadecimal directly?

Computers do not use hexadecimal, it is translated into binary for a computer to use.

What base is the hexadecimal number system?

Hex is a base 16 number system

Which digits and letters are used in hexadecimal?

0 1 2 3 4 5 6 7 8 9 A B C D E F

Why is it difficult for humans to read binary numbers?

The computer uses binary numbers and it is difficult for human beings to read them

Why do humans use hexadecimal?

The hexadecimal number system is easier for humans to use

In hexadecimal, which digits are used for values 0 to 9?

ten digits are used from 0 to 9

In hexadecimal, which symbols represent values 10 to 15?

A, B, C, D, E and F symbols are used

What decimal value does hexadecimal symbol A represent?

10

What decimal value does hexadecimal symbol B represent?

11

What decimal value does hexadecimal symbol C represent?

12

What decimal value does hexadecimal symbol D represent?

13

What decimal value does hexadecimal symbol E represent?

14

What decimal value does hexadecimal symbol F represent?

15

How many bits make up a single hex digit?

A 4-bit binary sequence.

How many hex digits are needed to write an 8-bit binary number?

two hex digits

How is hexadecimal used when identifying computing errors?

the hex number identifies the memory location of an error.

How is hexadecimal used in web design and image editing?

representing colours on web pages and image-editing software.

What format is used to represent colours in hexadecimal?

RRGGBB

In the #RRGGBB format, what does the '#' symbol indicate?

shows that the number has been written in hex format

In the #RRGGBB format, what does 'RR' represent?

reds

In the #RRGGBB format, what does 'GG' represent?

greens

In the #RRGGBB format, what does 'BB' represent?

blues

How many values exist for each of the three colours in hexadecimal format?

256 values

How many hex numbers are used for each colour in #RRGGBB format?

Two hex numbers

What colour is represented by the hexadecimal code #FFFF00?

yellow

In what format is all data represented in a computer system?

binary

By what method is an image displayed on a computer screen?

bitmap representation

What is another name for bitmap images?

raster images

What does bitmap representation refer to?

how patters of bits in a pixel maps to a specific colour

What is a pixel?

a tiny coloured square

How are pixels arranged in a bitmap image?

horizontal rows

How is the resolution of an image measured?

in the number of pixels per row (width) and the number of pixel rows (height)

What type of image quality does high resolution provide?

good quality

How is image size measured?

in the number of pixels per inch - ppi (also referred to as dots per inch – dpi)

What stands for PNG?

Portable Network Graphics

What stands for JPEG?

Joint Photographic Experts Group

What stands for GIF?

Graphics Interchange Format

What stands for TIFF?

Tagged Image File Format

What stands for PSD?

Photoshop Document

What stands for XCF?

Gimp Project File

What type of compression does PNG use?

lossless compression

What happens to image quality during PNG compression and decompression?

image quality is not compromised

What feature does PNG allow that is useful for logos and graphics?

transparent background

What type of compression does JPEG use?

lossy compression

What is the trade-off when using JPEG compression?

smaller file sizes but some loss of image quality

What compression types does TIFF support?

both lossless and lossy compression

When should PNG be used?

when you need lossless compression, transparency, and sharp details in graphics.

When should JPEG be chosen?

for photographs and images where a balance between file size and acceptable loss of quality is needed.

Why are most web graphics saved as JPGs?

to support download speeds.

When should TIFF be chosen?

when working with high-quality images, detailed graphics, and professional print projects.

Where did the term 'photoshopped' originate?

from the popular image editing software Adobe Photoshop.

What does the term 'photoshopped' describe?

an image that has been edited using software

What objects do vector graphics use?

geometrical objects, for example, curves, points and polygons.

What is a vector image made up of?

paths, each of which has a mathematical formula or vector.

What does a vector indicate using coordinates?

how the each part of the image is shaped and what colour it is bordered with or filled by

What does a data file for a vector image contain?

the points where the paths start and end, how much the paths curve and the colours that fill or border the paths.

What happens to resolution when a vector image is enlarged (scaled)?

it doesn’t lose resolution

What does .ai stand for?

Adobe Illustrator Document

What does .eps stand for?

Encapsulated Postscript

What does .ps stand for?

PostScript

What does .pdf stand for?

Portable Document Format

What does .svg stand for?

Scalable Vector Graphics

What does .swf stand for?

Shockwave Flash

Which takes up more storage space, a bitmap image or a vector image?

A bitmap image takes up more space than a vector image

Why is compression used on image files?

to reduce an image file’s size and also to change some of the attributes of an image file

What must be done to a compressed file when it is used?

a file has to be decompressed when used

What are the two types of compression?

Lossy compression and Lossless compression

What happens to data during lossy compression?

some data is removed and discarded

How can an image be compressed using lossy compression?

by reducing its amount of colours used

What size file does lossy compression produce?

a much smaller compressed image file

Where should lossy compression be used?

to place an image on the Web

What types of images is lossy compression not suitable for?

drawings or graphs

What happens to picture quality during lossless compression?

the quality of a picture remains the same and does not deteriorate.

What happens when a lossless compressed file is decompressed?

decompressed to its original quality and can be restored without any changes.

Are files reduced in size without loss of data in lossless compression?

Files are reduced in size without the loss of data.

What is Run Length Encoding (RLE)?

One method of lossless compression

What does Run Length Encoding look for in a file?

consecutive runs of the same data.

How does Run Length Encoding store consecutive runs of data?

stored as one item of data, instead of many.

How does Run Length Encoding represent a run of identical pixels?

by the colour value and the count of how many times it repeats.

Why is JPEG used for digital camera images?

due to its small size and quality of image

Why is GIF unsuitable for high-quality photographs?

Compresses images so much so that it is unsuitable for high-quality photographs where detail is required

What type of compression does GIF use?

lossy compression

What is image size?

simply the number of pixels that an image contains.

How is image size expressed?

height and width.

What determines the range of colours in an image?

The number of bits

What is colour depth?

The number of bits that determines the range of colours.

What is monochrome?

1 bit - we can store 2 colours, 0 (black) and 1 (white)

How many colours can be stored with 2 bits?

4

How many colours can be stored with 3 bits?

8

What elements are used to estimate image file size?

the image height in pixels, the image width in pixels, the colour depth per pixel

What is image resolution?

a way of describing how tightly packed the pixels are.

Why do low-resolution images look blocky or pixelated?

the pixels are larger and therefore, fewer are needed to fill the space.

How does higher resolution affect image file size?

The higher the resolution of an image, the larger its file size will be.

How is digital image resolution measured?

in pixels per inch (PPI).

What does 72ppi mean?

72 pixels in each square inch of the image.

What does 300ppi mean?

300 pixels in each square inch

What is metadata?

extra data contained in files, such as data about the file itself

How is sound represented on a computer system?

digital data.

How is analogue sound converted for a computer system?

converted (digitised) from its analogue format (a series of sound waves) into digital format (binary digits).