Data Representation Flashcards
Distinguish between bitmap and vector graphics
Bitmap images are made up of pixels, and vector images are made up of points and curves
Describe color depth and image resolution
What do computers use to store and process images?
The computers store and process images using binary codes so that you can see them on the screen.
What are the two forms that an image is usually presented in?
Bitmap images – made of small parts called pixels.
Vector images – made using coordinates and geometry.
What are vector images made up of?
Points and curves
What are bitmap images made up of?
Pixels (units of light)
Each pixel in an image is made up of…
binary numbers
How do you find the size of an image?
Height x width
Image resolution can be expressed as what?
The number of pixels that an image contains per inch.
Resolution is usually measured in…
dots per inch (dpi)
Magazines often use either…
300 dpi or even 600 dpi.
What is the resolution of a 100 by 70 pixel image?
100 * 70 = 7000 pixels
What do you need to have more colors in your images
You need more bits
What does color depth describe?
Color depth describes the number of bits of memory that are used to store the color information about each pixel in a bitmap image.
What does having 2-bits per pixel mean?
Having 2 bits per pixel means that you can use 4 colors in your image.
00 = white
01 = black
10 = gray
11 = blue
(2^n, and n is the number of bits)
What’s the equation for finding bits per pixel (aka color depth)?
2^n, n being the number of bits
What are two things that impact the file size?
Resolution and color depth
How much does 1 KB equal to?
1000 bytes
File size is normally measured in what?
Bytes
What is the file size of an image that is 800x800 pixels and has a color depth of 4 bits? Give your answer in KB.
Calculate the total pixels: 800800=640,000 pixels.
Calculate total bits: 640,0004=2,560,000 bits.
Convert bits to bytes: 2,560,000 / 8 =320,000 bytes.
Convert bytes to kilobytes: 320,000 / 1000=320 KB
What is the file size in bytes of a bitmapped graphic that is 100 * 100 pixels and has a color depth of 2 bits?
Calculate the total pixels: 100100=10,000 pixels.
Calculate total bits: 10,0002=20,000 bits.
Convert bits to bytes: 20,000 / 8 =2,500 bytes.
What does metadata mean?
Metadata means ‘data about data’.
What does metadata do?
Metadata is added to an image file to allow the file to be saved and reproduced accurately.
What are examples of metadata?
Image dimensions (e.g. width in pixels, height in pixels)
Color depth
File format – e.g. JPEG, GIF or PNG
Date and time of creation
Geographical location of creation
Details about the device used to create the image
Camera settings
What is the additive process?
Mixing red, green and blue colors (RGB) to project colors onto a screen
How do computer screens work?
Computer screens work by combining three colors. It begins with a black screen, and then colors are added using a process called “Additive process” by mixing red, green and blue colors (RGB).
How can different colors be shown on a screen using the additive process?
By adjusting the brightness of these lights
What are the numbers that are used to represent colors in computer graphics?
Numbers from 0 to 255
What do the colors 0-255 do in computer graphics?
They display different pixel brightnesses
What does it mean for the red value light to be at 0?6
The red colored pixel is completely off
What does it mean for the red value light to be at 255?
The red pixel is completely on
How many possibile values for all of the 3 primary colors are there?
There are in total of 256 possible values for each primary color, including 0. Therefore, a total of 256x256x256= 16,777,216 possible colors can be created.
What are the smallest and largest numbers of color bits (using 8) than can be represented by hexadecimal?
The smallest number 0 that can be represented using 8 bits is 00000000. And the largest number 255 that can be represented using 8 bits is 11111111.
How many possibilities are there for representing the three primary colors in 8 bits?
With 256 different possible values for three primary colors, 8 bits are needed to represent a number. Therefore, 28=2 x 2 x 2 x 2 x 2 x 2 x 2 x 2=256.
How many bits are required to represent 3 primary colors?
For three primary colors, 3x8=24 bits in total is required to represent a color.
Therefore, RGB (255, 51, 153) in binary number is…
111111110011001110011001
