Digital Imaging Fundamentals Ms. Hema C.R. School of Mechatronic Engineering

Hema - Digital Image Fundamental 2 The Digital Image  Digital imaging products like Photo CD, camera etc. enable capture and storage of film images electronically, to process them on the computer, much like the processing of text and drawings.  A film image is represented electronically by continuous analog wave forms.  A digital image is represented by digital values derived from sampling the analog image.

Hema - Digital Image Fundamental 3 The Digital Image  Analog values are continuous. Digital values are discrete electronic pulses that have been translated into strings of zeros and ones the only digits in a binary numbering system.

Hema - Digital Image Fundamental 4 The Digital Image  Before proceeding to take a closer look at the digital image, the difference between the two ways the computer stores image data has to be understood: Vector graphics Raster graphics.

Hema - Digital Image Fundamental 5 The Digital Image  Vector graphics, also known as object-oriented graphics, are created in various drawing programs

Hema - Digital Image Fundamental 6 The Digital Image  Vector images are stored as a display list describing the location and properties of the objects making up the image, such as shapes, arcs and lines.

Hema - Digital Image Fundamental 7 The Digital Image  Raster graphics, also known as bit-mapped graphics, are created by scanners and digital cameras.  From this point on only raster images will be considered.

Hema - Digital Image Fundamental 8 The Digital Image  Raster images are "painted" across the computer screen in an array of square elements called pixels.  Pixel is short for picture element

Hema - Digital Image Fundamental 9 The Digital Image  Each pixel is stored in an area of memory called a bit-map.  Each pixel has a numbered address.

Hema - Digital Image Fundamental 10 The Digital Image  Storing the formula for creating a vector image takes only a few kilobytes.  Storing the location and value of each pixel in a raster image can take thousands of times more memory.

Hema - Digital Image Fundamental 11 The Digital Image  The quality of a raster image is determined at capture by two factors: spatial resolution brightness resolution.

Hema - Digital Image Fundamental 12 The Digital Image  Pixel size is determined by the rate at which the scanner samples the image. A long sampling interval produces an image low in spatial resolution. A shorter interval produces higher spatial resolution

Hema - Digital Image Fundamental 13 The Digital Image  The brightness or color value of each pixel is defined by one bit or by a group of bits.  The more bits used, the higher the brightness resolution.

Hema - Digital Image Fundamental 14 The Digital Image  A 1-bit image can have only 2 values, black or white.  1-bit images simulate grays by grouping black and white pixels. This process is called dithering or half toning.

Hema - Digital Image Fundamental 15 The Digital Image  An 8-bit gray-scale image displays 256 levels of brightness. Each pixel is black, white or one of 254 shades of gray.

Hema - Digital Image Fundamental 16 The Digital Image  A higher resolution 12-bit medical image provides more than 4000 brightness levels.

Hema - Digital Image Fundamental 17 The Digital Image  In a 24-bit image, each pixel is described by three 8- bit sets of numbers representing the brightness values for red, green and blue.

Hema - Digital Image Fundamental 18 The Digital Image  High resolution 24-bit images display 16.7 million colors.

Hema - Digital Image Fundamental 19 The Digital Image  Each pixel in a 24-bit image has one of 256 brightness values for red, green and blue

Digital Imaging Fundamentals The end