1.2 Units and Data Flashcards
(32 cards)
What are two ways of storing images in binary?
Bitmap and a vector
What is made from a bitmap?
An image made up of different coloured squares, (pixels) each having a binary value
What is made from a vector?
The mathematics to store the square are stored e.g. a circle can be drawn just by storing the details of X and Y coordinates from the middle, the radius, the width and colour
What is stored as a bitmap?
Photographs not made up of simple shapes
What is stored as a vector?
Technical drawings, logos and clipart
What is metadata?
Additional data is stored along with the image to define the width, height, colour depth, and palette. (It allows the computer to take the binary raw data and make the correct resolution image)
The greater the colour depth and resolution…
the larger the file size of the image
What is each pixel of a bitmap stored in?
Binary
The number of bits required for each pixel depends on …
Number of colours required
e.g. 1 bit has 2 values: black and white
2 bits have 4 possible values : 00,01,10,11. Therefore 2 bits can store 4 colours
How is number of colours calculated?
2^n where n is the number of bits for each pixel
What are photographs stored in?
24-bit colour depth, Each pixel is 2 bits. This is 2^24 = over 16 million colours. The number of different colours the human eye can see
What is sound?
A vibration that propagates as an audible wave of pressure through the air.
What is analogue to digital conversion?
Convert what is an analogue signal into a digital binary one.
What affects quality of a digitally converted sound wave?
Sample rate (speed)
Bit depth (detail)
What is sample rate?
How often per second we are sampling the original analogue sound (record the amplitude of a sound wave). - number of samples stored per second)
What is the bit depth?
The amount of detail we are capturing with each sample (number of bits stored per sample)
What happens when you record a sample more often?
The more often you record a sample the smoother the playback will sound.
The higher the number of samples per second,
The higher the quality the sound will be but also the larger the file size, as we are storing more data per second.
What is the sound file size?
The total number of bits in a sound. Calculated as (number of samples per second) x (number of bits per sample) x (length of sample in seconds)
The higher the number of bits,
the greater the quality of the sound and the larger the file size
Duration
how many seconds of audio the sound file contains
What does compression do?
Reduces number of bits in a file making storage capacity of the file lower and making data transfer useful.
Why is compression useful?
More data can be stored on a storage device and transferred in a smaller amount of time.
What happens in lossy compression?
- Some of the data is lost and cannot be recovered.
This greatly reduces file size and the quality of the image/sound. - It is suitable for images, sound, video
- Cannot be used on text and executable files.
