

Digital Image Processing





Image – a two-dimensional function f(x,y).



Where, x and y = Spatial (plane) coordinates



Image is a 2-D array specifically arranged in rows and columns.

Color image - It has 24 bit color depth = 8 x 8 x 8 bits = 256 x 256 x 256 colors = ~16 million colors











Grayscale image - In a (8-bit) grayscale image each picture element has an assigned intensity that ranges from 0 to 255. A grey scale image is not a black and white image, but includes many shades of grey.











Gray level of image - Amplitude of f at any pair of coordinates (x,y) .





Digital image - When x, y and the amplitude values of f are all finite, discrete quantities.

Digital image is composed of a finite number of elements, each of which has a particular location and value.





Pixel - the element of a digital image.













Field of digital image processing - Processing digital images by means of a digital computer

Humans are limited to the visual band of the electromagnetic spectrum, imaging machine cover almost the entire electromagnetic spectrum, ranging from gamma to radio waves.





Image processing - Discipline in which both input and output of process are images.





Computer vision – To use computers to imitate human vision, including learning and being able to make inferences and take actions based on visual inputs.





Image analysis / Image understanding - The area in between image processing and computer vision.





Levels of Image processing -

1. Low level processes - Image preprocessing to reduce noise, contrast enhancement, and image sharpening.

Both its inputs and outputs are images.





2. Mid level processes - Segmentation and classification.

It s information sources for the most part are images, however its yields are characteristics (e.g., contours, edges etc.) extricated from those images.





3. High level processes - “making sense” of an ensemble of recognized objects and performing cognitive functions normally associated with vision.

Benefits of digital image processing -

Pictorial information gets improved for human interpretation

Improvement in processing of Image data for storage ,transmission and representation

Autonomous machine perception becomes easier



