IMT Autumn Term Flashcards
What is a digital image?
A rectangular grid of coloured dots called picture elements or pixels
What is a digital image made up of a grid of pixels called?
A raster image
Why use raster images?
Representing images as grids of pixels lets us store them in the computer’s memory
How is a raster image stored as?
As a list of numbers, which specify the colours of its pixels
What type of colour model is RGB?
Additive
What type of colour model is CMYK?
Subtractive
What does RGB stand for?
Red, green and blue
What does CMYK stand for?
Cyan, magenta, yellow, and key (black)
What does the ‘A’ stand for in the RBGA colour model?
The alpha channel
Which file formats support transparency (alpha channels)?
BMP, PNG and TIFF
Which file formats do not support transparency (alpha channels)?
PNG and GIF (GIF however allows you to set one colour to be a transparent background colour)
What is colour depth/bit depth?
The number of bits in memory used to store a pixel
Does a greater colour depth increase or decrease file size?
Increase
What does insufficient colour depth lead to?
Banding
What is the artistic use of banding called?
Posterization
What does gamut mean?
Gamut refers to the range of colours that can be reproduced by a colour model
Which of the two colour models (RBG and CMYK) have a larger gamut?
RGB
What does pixel resolution mean?
It refers to the number of pixels that make up an image
How does a higher pixel resolution impact on an image?
It gives the image more detail and quality
What is spatial resolution?
The relationship between the physical size and pixel dimensions
What is spatial resolution expressed in for monitors?
Pixels per inch (PPI)
What is spatial resolution expressed in for print?
Dots per inch (DPI)
What is aspect ratio?
The proportional relationship between the width and height of an image
What aspect ratio is used in early film?
4:3
What aspect ratio is used for HD TV?
16:9
What aspect ratio is used for monoscopic VR
2:1
What does HSV stand for?
Hue (H), saturation (S) and brightness (V)
Why use the HSV colour model?
It is easier to estimate the colour value and changes to hue or brightness do not require changes to all values
What is a selection?
An isolated region of an image
