Images are either vectors or bitmaps. Bitmap images are made out of small parts called pixels. Vector images are made using coordinates and geometry. Images can be compressed to reduce file size.
What is a pixel?
It is an animated object in a game that can move or collide with other objects
It is a single coloured 'dot' in a bitmap image
It is a pair of coordinates that tell the computer where to draw a point on the screen
Why are vector files often high quality, even when you zoom in or out of the image?
Because the precise position of each part of the image can be recalculated using the coordinates and mathematical formulae
Because engineers and people that use vector files often use more powerful computers than people at home
Because screens and printers are much more detailed than they used to be
What is resolution?
It is the total number of pixels in an image
It is a measure of how many pixels are used in a given area
It is a measure of how much an image has been compressed
What does 'dpi' mean?
The number of colours supported by the image format
The number of dots that can be plotted each second on a screen or printer
The number of dots used per horizontal inch in the image
Why do bitmap images often appear blocky if you enlarge them too much?
Because there is only a limited amount of detail in the bitmap image
Because of rounding errors in the calculations for the coordinates and formulae being used to draw the image
Because adding new pixels to the image would take up all of the computer's memory as you zoom in
What is the 'colour depth' of a raster image?
The number of alternative colours that a pixel can use
The number of different colours actually used in the image
The width of the image measured in pixels
Which compressed file format is often used for storing digital camera images?
Which of these is NOT true about compressing an image using JPG?
The file size of the compressed image is always much smaller than the original image
The image may lose some details that are not actually visible to the human eye
JPG can compress photographs better than it can diagrams containing large blocks of the same colour
What is metadata?
Data that is stored in the computer's RAM
Data that is downloaded from photo-sharing websites
Data that describes other data, eg how it is structured or organised
Which of these formats uses lossless compression?