representing images Flashcards
bit patterns, images, sound and other data (25 cards)
what is a bitmap image?
an image formed from rows of different coloured pixels
what is a pixel?
this is the smallest element of a bitmap image.
how do you calculate a bitmap resolution?
by calculating the area of the image which is made using pixels
what does resolution in bitmap mean?
the quality of the image, how many pixels there are in an image and it’s scale size.
how many bits per pixel is required for 256 colours
8-bit, 2 to the power 8 gives 256.
what does rasterization mean?
creating a bitmap
name four common bitmap files
- JPG
- JPEG
- PNG
- GIF
how do you calculate the bit depth?
2 to the power n.
what is the range for RGB values?
RBG (red, green and blue) is ranged between 0 - 255
how do you calculate the file size?
the number of pixels * bit depth. you then divide by 8 to convert bits to bytes. You would always need to give your answer in bytes if it is not stated in the exam.
what is metadata?
this is data about data that is stored in the same file as the image data.
what is colour depth and how is it calculated?
the number of bits in a single pixel.
give 3 example of a meta data
- resolution of the image
- location of the image
- time the image was taken
what is the standardized number of colours a pixel can be for an RGB display
16, 777, 216
what does the term “resolution independent” mean?
this is when resizing something does not make the resolution change.
what are vector graphics?
these are images that are made up of lists of objects and their properties (attributes).
what are drawing lists?
The list of images that the vector graphics have to create.
name some properties when creating a vector graphic
- positions; x and y coordinates
- dimensions; width and height
- appearance; fill, stroke, stroke-width
- note that there is no colour property by itself, you have to state this in the fill, stroke property.
why are vectors resolution independent?
This is because they are made of equations. If you want it to become bigger you might multiply it by 2 or any other number which gives it, its highest resolution.
name 3 advantages of using a bitmap?
- can be compressed into smaller sizes
- simple to edit
- has a better visual appeal and can go into depth with details.
name 2 advantages of using vectors
- resolution independent
- less storage space
name 4 disadvantages of using bitmaps
- often has large file sizes
- poor scalability
- resolution dependent
- limited colour depth
name 2 disadvantage for using vectors
- difficult to create a gradient
- not easy to compress vectors
in what real-world situations would you use bitmaps?
- photographs
- represent images on the computer
