Images Flashcards
What is a vector image?
Created using CAD packages and is made up of components defined by geometric formulae and associated properties such as line-colour and style.
How is a vector image stored?
Contains a file called a drawing list which contains a command for each object included in the image such as a list of attributes that define properties of the object. Properties include gemoetric data such as the radius of a circle if it is used, line thickness, colour of a line, and fill colour.
Vector images are scalable if resized as the objects are recalculated.
What is a bitmap image?
An image which is made up of pixels.
Give examples of where bitmap images can be needed
Capturing a image via camera/scanner
Drawing an image in a drawing package
Explain what is meant by a pixel
A picture element which is the smallest identifiable component of a bitmap image, defined by two properties: position in the bitmap matrix and its colour
Explain how a pixel is formed
One bit represents the colour so that the pixel is either black or white.
4 bits = grey scale
8 bits = coloured image
E.g. a 1 bit image can only store 21 pixels which equals
to 2. Therefore, a 1 bit image is monochromatic.
An image with n bits has 2
n colors per pixel
What is meant by colour depth?
The number of bits per pixel
The higher the color depth, the better color quality.
The higher the color depth, the larger the file size.
What is meant by the resolution of the image?
It is the number of pixels per row x the number of rows.
What do you need to consider when considering resolution
The resolution of the image versus the maximum resolution of the image
What is the scalability like for a bitmap image?
The image is scalable but when it is scaled, the number of pixels does not change (increase/decrease). Good quality images, when scaled, are hard to see changes to the image. If an image is magnified too far, the quality deteriorates and the individual pixels can be seen.
How are bitmap images stored?
A large file occupies more memory space and takes longer to transmit across a network. Vector images are smaller than bitmap files.
Bitmap files has to store pixel data as well as a header that defines the resolution of the image and its coding scheme for pixel colours.
How do you calculate the minimum size of a bitmap image?
It is minimum as it does not take into account the header.
Resolution height x resolution width x number of bits
i.e.
1366 x 768 x 24 = 25 178 112 bits.
To convert to MB you have to convert bits to bytes and then bytes to MB
What is the resolution of this image in MB.
800x400 resolution with 24 bits?
0.915
State the different memory sizes from smallest to largest
Bit Byte KB MB GB TB PB
