Text and Images Flashcards
What is a bitmap image?
A collection of pixels where each pixel is assigned a value that represents it’s colour.
What is a pixel?
picture element
The smallest block of colour in an image
What is colour/bit depth?
The number of bits used to represent the colour of a single pixel
Rule for colour depth
For n bits you can store 2^n different colour codes
What is image resolution?
The number of pixels in the image
image size
number of pixels x colour depth
What is meant by image metadata?
Image files usually also contain metadata .
Metadata means ‘data about data’
It provides additional information about the image.
Computers needs this data to interpret the file
6 examples of image metadata
file format - eg JPG, GIF, BMP, PNG resolution colour depth time/date the image was taken camera settings GPS data
how captured camera images are converted to digital photo files
Image is turned into pixels
Pixels form a grid
Each pixel is give a binary value
Each pixel is given a colour
Pixels are stored in the correct sequence
Meta data is also stored about the image e.g. dimensions/resolution/colour depth
Different file formats are used e.g. JPEG
What happens when you increase the colour depth of an image?
The quality of the image increases
You are more accurately able to represent the range of colours
Also increases the memory size of the image
What happens when you increase the number of pixels in an image?
The density of pixels in the same sized area increases
improving sharpness
Can enlarge without visible loss of quality
Increases the memory size of the image
Examples of character sets
ASCII
Extended ASCII
Unicode
What is a character set?
A character set is a complete set of the characters and their character codes that can be recognised by a computer system.
What is character code?
A value/binary number that represents a character
What is ASCII?
American Standard Code for Information Interchange.
A character set used to represent 128 characters
It uses 7 bits
