Unit 3 - Data Representation
What are bitmap images made up of?
-A grid of pixels
What are the 2 most common types of alphanumeric data?
-ASCII -Unicode
What are the 2 types of image?
-Bitmap (raster) with grids of pixels -Vector (object) composed of graphical objects that can be resized
What are vector images used for?
-Complex drawings
What is the effect of enlarging bitmap images?
-Enlargement produces jagged edges
What are examples of bitmap image formats?
-GIF -JPEG -TIFF -BMP -PNG
What are vector images made up of?
-Geometrically defined shapes
What requirements are required for vector images?
-Higher computational requirements
How do you represent a number using 2's complement?
-If positive, represent the same as unsigned binary number -If negative, find the positive representation first, then invert all digits after the first 1 that appears from the left most bit
What is the resolution of output of a bitmap image limited by?
-Image resolution
What requirements are required for bitmap images?
-Large storage requirements
What is colour depth?
-Number of bits used to represent a single colour
What is image resolution?
-Number of pixels used to represent an image
What is frame rate?
-Number of still images recorded every second, measured in frames per second (fps)
What is the effect of enlarging vector images?
-Objects scale smoothly
What is the resolution of output of a vector image limited by?
-Output device
What are the input devices to form a bitmap images?
-Scanners -Digital cameras
What are the 2 ways of representing a signed binary integer?
-Sign and magnitude -Two's complement (most common)
What are the problems with the sign and magnitude method?
-Sign and magnitude computation algorithms complex and difficult to implement in hardware -Can only represent a total of 2^(n-1) as you lose the left most bit to represent +/- -0 has 2 representations -Addition & subtraction requires the sign bit to be handled separately
What is the formula for the total number of values an unsigned binary number of n-bits can represent?
-Total of 2^n values
How do you represent a number using sign and magnitude?
-Use left-most bit for sign (0 for +, 1 for -) -Rest of the bits used for magnitude
What are bitmap images used for?
-Used for realistic images with continuous variations in shading, colour, shape and texture
-What is the range for an n-bit sign and magnitude number?
- -2^(n-1) + 1.........-0 - +0.......... 2^(n-1) - 1
What is the range of a 2's complement number of n-bits?
- -2^(n-1).....2^(n-1) - 1
What is the range of values an unsigned binary number of n-bits can represent?
- 0......2^n - 1
What is the formula for the total number of values a 2' complement binary number of n-bits can represent?
- 2^n numbers
What is the formula for calculating the size of bitmap images?
Number of pixel rows * number of pixel columns * colour depth in bits
