Storing Images Flashcards
What are most images?
Bitmap images
What are bitmap images made up of?
Tiny dots called pixels
How is the colour of each pixel represented?
By binary code
What is the number of colour in the image related to?
The number of bits the code has
How many bits does a black and white image have?
Black and white image uses two colours so it would need a bit for each pixel. 0-white, 1-black
How many colours would a 2-bit image have?
4 colours. Each pixel, one of 4 binary values- 00, 01. 10 and 11
What is the colour depth?
Number of bits used for each pixel?
How do you find the total number of colours?
2ⁿ ( with n being the number of bits per pixel or bpp)
1 bit = 2¹ = 2 colours
4 bit = 2⁴ = 16 colours
24 bit = 2²⁴= 16,777,216 colours
What bit depth do most devices use?
Most devices use a 24-bit depth with 8 bits for the level of red, green & blue in each pixel.
This colour depth produces more colours than the human eye can see (10 million)
What is the image resolution?
Number of pixels in the image (Width x Height)
What does a higher resolution mean?
The more pixels image made up of = better quality of image
How is File size (in bits) calculated?
image resolution x colour depth
width x depth x colour depth
What does using a greater image resolution/ colour depth do?
It means more bits in the image which can higher image quality but increased file size
What is Metadata?
Information stored in image files which helps the computer recreate image on screen from binary data in each pixel.
What does Metadata include?
File format, height, width, colour depth and resolution
