Computer Science - Representing Characters and Images in a computer + graphics 💻 Flashcards
What is a character set?
The set of symbols that may be represented by a computer at a particular time.
What are the two main internationally agreed character sets?
ASCII and Unicode
What does ASCII stand for?
American Standard Code for Information Interchange.
Initially, how many bits did ASCII use and how many characters could it represent?
It used 7 bits out of the 8 bit byte, which meant it could represent 128 different characters (2⁷)
How many bits does the extended ASCII use and how many characters can it represent?
It uses all 8 bits and can represent up to 256 characters (2⁸)
In ASCII, upper case letters are stored as the numbers:
65 to 90
In ASCII, lower case letters are stored as the numbers:
97 to 122
In ASCII, numeric digits are stored as the numbers:
48 to 57
In ASCII, the space character is stored as the number:
32
What is unicode?
Unicode is an international standard character set which uses 16 bits to represent the character set.
What is the goal of unicode?
The goal of unicode is to specify a code matching every character needed by every written human language, It aims to be understood by all computer platforms.
The first 256 characters of unicode are…
Identical to ASCII
What are graphics?
Graphics are the display of images and drawings on the computer. It is digitized, meaning that it is turned into a sequence of numbers understandable by the computer.
What is a pixel?
A tiny square of colour, many of these together can form a digital image.
What is “pixel” short for?
It is short for “picture element”
How does a computer know what colour a pixel is?
Each pixel has a specific number which tells the computer what colour the pixel should be.
What is the process of digitization?
The process that takes an image and turns it into a set of pixels.
A computer monitor is made up of…
A computer monitor is made up of millions of tiny squares (pixels)
The more pixels, the…
The more pixels, the better an image looks
What are the two types of graphics?
Bitmapped/raster graphics and Vector graphics.
What is a bitmap?
A bitmap is a method for storing images using pixels.
Why are bitmap graphics called bitmap graphics?
Because it is a “map” of where the “bits” of information are stored.
The information in bitmap graphics are stored as…
The information in bitmap graphics are stored as a sequence of numbers defining the colour of each pixel.
In a simple black and white image, what does a bitmap need to know?
It needs to know if a pixel is “on” or “off”, which can be stored as a 0 or a 1.
In a colour image, what does a bitmap need to know?
It needs lot of bits, normally 24, to store the colour values of each pixel.
What are the common bitmap file formats?
.jpeg, .jpg, .png, .tiff, .gif, .psd (photoshop)
What are the common bitmap editing programs?
Microsoft paint, Adobe photoshop, Corel photo paint & Corel photo paint shop pro (what even is corel-), and The GIMP (all hail THE GIMP)
What is vector?
Graphics made out of geometric shapes (lines, curves) and coordinates to precisely define the parts of the image. Information is stored as formulas.
What are the common vector file formats?
.ai, .cdr, .cmx, .svg, .cgm, .dxf, .wmf
What are the common vector editing programs?
Adobe illustrator, CorelDraw, Xara Xtreme, Serif DrawPlus, Inkscape
What are some key points about vector images?
- Scalable
- Resolution independent
- No background
- Cartoon-like
- Innapropriate for photorealistic images
What are some key points about bitmap images?
- Made with pixels in a grid
- Resolution dependent
- Resizing to a larger size reduces quality
- Easily converted
- Restricted to rectangle
- Minimal support for transparency
Which type of graphic is scalable without loss in quality?
Vector
Which type of graphic is suitable for photographic images?
Bitmap
Which type of graphic takes up more storage?
Bitmap
Which type of graphic uses more processing power?
Vector
Which type of graphic is suitable for logo designs?
Mostly vector, but bitmap graphics can still be used for logos to create a more natural brand.
Which type of graphic is suitable for digital painting/art?
Bitmap
Which type of graphic can group individual elements?
Vector
Which type of graphic can be more easily edited in any program?
Vector
Which type of graphic can create more detailed images?
Bitmap
Why do bitmap graphics take up more storage?
Each pixel has to be stored, and even “blank” pixels contribute to file size.
