What Is Digital Image Processing？

What Is Digital Image Processing？

Table of content.

What Is Digital Image Processing？

★ Image

An image is an entity obtained by observing the objective world through various observation systems, in different forms and by different means. It can directly or indirectly act on the human eye and subsequently produce visual perception.

★ Images and Information

Approximately 75% of the information humans obtain from the external (objective) world comes from the visual system.

★ Image Representation

A digital image can be represented as a 2-D array:

f(x,y)f(x, y)f(x,y)

  • x, y: Coordinates of a point in the 2-D spatial XY plane

  • f: The value of property F at position (x,y)(x, y)(x,y)

  • x, y can take any real values

  • Property F can correspond to different physical quantities; in grayscale images, it represents gray level (intensity)

★ Image Elements

An image is a collection of many image elements.

  • 2-D image: Pixel (picture element), commonly called pixel

  • 3-D image: Voxel (volume element), commonly called voxel

Extensions:

f(x,y)→f(x,y,z),f(x,y,t)f(x, y) \rightarrow f(x, y, z),\quad f(x, y, t)f(x,y)→f(x,y,z),f(x,y,t)

★ Image Display Examples

★ Digital Image Representation

The input and output of digital images are collectively referred to as digital image processing.

From image processing to computer vision, there exists a continuous and unified progression:

  • Image Processing: Image → Image

  • Image Analysis: Image → Data

  • Image Understanding: Image → Interpretation

 

Origins of Digital Image Processing

★ Bartlane Cable Picture Transmission System

  • 1921: Telegraph printers used special characters to print on encoded paper tape. Output devices evolved from general-purpose to specialized systems.

  • 1922: Images were transmitted twice across the Atlantic Ocean using punched tape; image communication systems incorporated source coding and channel coding to detect errors.

  • 1929: Images were transmitted from London to New York via cable, increasing grayscale levels from the early 5 levels to 15 levels.

 

Historical Development

  • The first large-scale computers powerful enough to perform meaningful image processing tasks appeared in the early 1960s, initially used for satellite image processing, such as correcting various image distortions from spacecraft TV cameras.

  • In the late 1960s and 1970s, digital image processing began to be applied in medical imaging, earth resource remote sensing, and astronomy.

  • 1895: Wilhelm Conrad Röntgen discovered X-rays, winning the 1901 Nobel Prize in Physics.

  • 1975: Godfrey N. Hounsfield and Allan M. Cormack invented Computed Tomography (CT), winning the 1979 Nobel Prize in Physiology or Medicine.

  • From the 1960s to the present, digital image processing has also been widely applied in geography, archaeology, biology, national defense, and industrial fields.

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