IT 2 - storing and compressing Images Flashcards
What are the different Data types?
- A single (two-byte) integer
- Array of two (one-byte) integers
- A string of 2 characters
What are multi-byte integers?
8-bit: 1 byte (0-255)
16 bit: 2 bytes (0-65535)
32 bit: 4 bytes
64 bit: 8 bytes
What do floating-point numbers store>?
Digits and magnitude
What are the 3 components of floating point numbers?
- sign - 1 bit
- Mantissa (fraction, significant) - 23 bits
- Exponent (magnitude) - 8 bits
What is each known point?
Pixel or voxel
What are multidimensional images?
Array of pixels
What is bit?
The smallest unit of storage
A bit stores just a 0 or 1
What is one byte?
Collection of 8 bits
Mathematically what does n bits yield?
2^n patterns
What are the different types of bytes?
Kilobyte, KB, about 1 thousand bytes
Megabyte, MB, about 1 million bytes
Gigabyte, GB, about 1 billion bytes
Terabyte, TB, about 1 trillion bytes (rare)
What are floating-point numbers?
Store numbers that have a decimal in it
Numbers can be very very big or small
Why is floating point binary efficient?
Efficient use of a computer register to represent extremely large values or small, or values that require a high degree of precision
What is floating point binary similar to?
Standard scientific notation in base 10
In 2D array what can compiler follow?
- Row Major
- Column Major
mapping
Why are arrays always created in single dimension in memory?
Memory is linear. and having single integer address
What is row major order?
Method of representing multi-dimensional array in sequential memory
Elements of array are arranged sequentially row by row
Why is Huffman code a type of prefix code?
distinguish consecutive characters because no code is the
prefix of any other code
Where is Huffman code generated from?
histogram, in
which case it is optimal, or from predicted probabilities
What is Run-length encoding (RLE)?
A form of lossless compression
What is RLE?
A simple method of compressing data by specifying the number of times a character or pixel colour repeats followed by value of character or pixel.
What is the aim of RLE?
Reduce no. of bits used to represent a set of data
less storage space and be quicker to transfer
What is lossless compression?
None of the original data is lost when compressed
How to calculate raw size image?
size = X x Y x Z x bytes
