Introduction to image processing

Image : An image is an array, or a matrix, of square pixels (picture elements) arranged in columns and rows. An image is a rectangular grid of pixels. It has a definite height and a definite width counted in pixels.

Each pixel has a color. The color is a 32-bit integer. The first eight bits determine the redness of the pixel, the next eight bits the greenness, the next eight bits the blueness, and the remaining eight bits the transparency of the pixel.

1 1 1 1 1 1 1 1	1 1 1 1 1 1 1 1	1 1 1 1 1 1 1 1	1 1 1 1 1 1 1 1
Transparency	Red	Green	Blue

Types of Image - 

• Analog images
• Digital image

Analog images :  are the type of images that we, as humans, look at.  They include such things as photographs, paintings, TV images, and all of our medical images recorded on film or displayed on various display devices, like computer monitors.  What we see in an analog image is various levels of brightness (or film density) and colors.  It is generally continuous and not broken into many small individual pieces.

Digital Image : DIGITAL IMAGES are electronic snapshots taken of a scene or scanned from documents, such as photographs, manuscripts, printed texts, and artwork. The digital image is sampled and mapped as a grid of dots or picture elements (pixels). Each pixel is assigned a tonal value (black, white, shades of gray or color), which is represented in binary code (zeros and ones). The binary digits ("bits") for each pixel are stored in a sequence by a computer and often reduced to a mathematical representation (compressed). The bits are then interpreted and read by the computer to produce an analog version for display or printing.
The advantage of digital images is that they can be processed, in many ways, by computer systems.

Pixel Values: As shown in this bitonal image, each pixel is assigned a tonal value, in this example 0 for black and 1 for white. 

Image processing : 

Image processing is a method to convert an image into digital form and perform some operations on it, in order to get an enhanced image or to extract some useful information form it.

• The two types of methods used for Image Processing
• Analog Image Processing : Analog or visual techniques of image processing can be used for the hard copies like printouts and photographs
• Digital Image Processing : Digital Processing techniques help in manipulation of the digital images by using computers. As raw data from imaging sensors from satellite platform contains deficiencies.

Image processing involves changing the nature of an image in order to either

• 1. improve its pictorial information for human interpretation, 
• 2. render it more suitable for autonomous machine perception. 

We shall be concerned with digital image processing, which involves using a computer to change the nature of a digital image (see below). It is necessary to realize that these two aspects represent two separate but equally important aspects of image processing.
A procedure which satisfies condition

• a procedure which makes an image “look better”—may be the very worst procedure for satisfying condition 
• Humans like their images to be sharp, clear and detailed; machines prefer their images to be simple and uncluttered.

Image Sharpening:

Original Image                   After Edges Detection

Image Noisy Removal

De-blurred

Edges Detection