Images and Sound 1.2 Flashcards
types of image files - bitmap
BMP
JPG
GIF
PNG
TIFF
types of image files - vector
SVG
Bitmap images
-made from pixels
pixel is given
- a colour
-binary number which represents that colour
image resolution
the concentration of pixels within a
specific area
Increasing the number of colours in bitmap
More bits per pixel =
more colour combinations
bit depth
number of colours
higher bit depth
better variety of colours
bit depth formula
2 to the power of n
n = bits
size of a bitmap image
measured in pixels (width x height).
colours in pixel
Each pixel has a proportion
of red, green and blue
-makes one colour
colour values
expressed in
software as denary RGB values and in hexadecimal
metadata
Colour depth in bits per pixel
Resolution (Height and width in pixels)
Date created
Author
pros of colour values being in hex
-easier to read/write = reduces errors
RGB value range
-0 to 255
-each colour must be 8 bits to store range
entire pixel bit range
3 * 8 = 24 bits
transparency channel
-32 bits per pixel 8 bits are given
-allow a background to show through
image size in bits
width * height * colour depth
image size in bytes
(width * height * colour depth) /8
analogue sound signals are
continuous
Digital signals are
discrete
how is Sound digitized
by repeatedly measuring and
recording the sound wave
A to D converters
Sounds is converted to a digital form
= stored + processed by a computer
An Analogue to Digital Convertor (ADC)
is used to
convert inputs to digital signals
A Digital to Audio Convertor (DAC)
is used to
convert digital signals to outputs
sound sampling
measurement of amplitude of a
sound wave at a given time
how is sound sampled
-sample resolution (bit depth)
-sampling rate
sampling rate
number of samples taken per second
(Hz)
Sample resolution
The number of bits used to record
each measurement
More bits used per sample =
- the height of the wave to be more accurately measured
- increases file size
Hertz
1Hz = 1 sample per second
sampling rate frequency
The greater the frequency, the greater the accuracy, and file size
Calculating sound file sizes
sample rate x bit depth x duration
Recording quality improves:
the more frequent
the more accurately recorded the wave height
Increasing the sampling rate (frequency) =
means
recording more data points
Increasing the bit-rate =
improves the accuracy of each
data point
Lossy compression
removes sounds that
we can’t easily hear or that is unecessary
Lossy compression cons
-leaves out some data
=affects quality
Lossy compression pros
useful for storing,
downloading or streaming
-as it is smaller
Lossless compression
-reduce the file size
when compressed but do not
lose any information
-can be decompressed
eg of lossless
FLAC (Free Lossless Audio Codec)
ALAC (Apple Lossless Audio Codec)
WMA Lossless
(Windows Media Audio)
