2.6 Images Flashcards
How are all images represented?
as strings of 1s and 0s
pixels
a digital image is composed of many small points of colour
each one is called a pixel (picture element)
each pixel has its own colour
the greater the number of pixels, the greater the detail in the picture
image size
the size of an image is the number of pixels in the width W and height H
when a small image is enlarged to cover a larger area it is less sharp as there are fewer pixels per unit area
it has a lower resolution
resolution
number of pixels per unit area
colour depth
number of bits used to encode the colour of each pixel
the more bits are used, the greater the number of actual colours that can be represented in the image
modern cameras and smartphones produce images with a colour depth of 24 bits
image file size
-depends on image size and bit depth
W x H x D (colour depth)
(+ 10% extra for metadata)
-the better the image quality the larger the file
large file sizes can be a problem if they are transferred electronically or storage space is limited
metadata
extra information about the image included with the image
can include:
- make and model of the camera
- dimensions of the image and file size
- speed and aperture settings
- GPS data showing the location where the image was taken
Calculate the file size in MB of an image with the dimensions of 4100 x 2700 pixels and a colour depth of 24 bits.
You may use the decimal prefix 1000 in your calculation. [3]
33.2 MB
+ 10%
Describe the factors that affect the quality of a digital image [4]
number of pixels that make it up
an image with a greater pixel height and width has a better quality than one with a lower
numer of bits used to encode the colour of each pixel is called the colour depth
if more bits are used, more colours can be displayed
if more colours are used then very small colour changes can be represented in the image, increasing the detail
