Digital image processing
It allows a much wider range of algorithms to be applied to the input data and can avoid problems such as the build-up of noise and distortion during processing.
[5] Many of the techniques of digital image processing, or digital picture processing as it often was called, were developed in the 1960s, at Bell Laboratories, the Jet Propulsion Laboratory, Massachusetts Institute of Technology, University of Maryland, and a few other research facilities, with application to satellite imagery, wire-photo standards conversion, medical imaging, videophone, character recognition, and photograph enhancement.
They used image processing techniques such as geometric correction, gradation transformation, noise removal, etc.
on the thousands of lunar photos sent back by the Space Detector Ranger 7 in 1964, taking into account the position of the Sun and the environment of the Moon.
Later, more complex image processing was performed on the nearly 100,000 photos sent back by the spacecraft, so that the topographic map, color map and panoramic mosaic of the Moon were obtained, which achieved extraordinary results and laid a solid foundation for human landing on the Moon.
That changed in the 1970s, when digital image processing proliferated as cheaper computers and dedicated hardware became available.
This led to images being processed in real-time, for some dedicated problems such as television standards conversion.
As general-purpose computers became faster, they started to take over the role of dedicated hardware for all but the most specialized and computer-intensive operations.
[8] The charge-coupled device was invented by Willard S. Boyle and George E. Smith at Bell Labs in 1969.
As it was fairly straightforward to fabricate a series of MOS capacitors in a row, they connected a suitable voltage to them so that the charge could be stepped along from one to the next.
This was enabled by advances in MOS semiconductor device fabrication, with MOSFET scaling reaching smaller micron and then sub-micron levels.
The first optical mouse, invented by Richard F. Lyon at Xerox in 1980, used a 5 μm NMOS integrated circuit sensor chip.
[26] DCT compression became the basis for JPEG, which was introduced by the Joint Photographic Experts Group in 1992.
[30] Medical imaging techniques produce very large amounts of data, especially from CT, MRI and PET modalities.
The cost and feasibility of accessing large image data sets over low or various bandwidths are further addressed by use of another DICOM standard, called JPIP, to enable efficient streaming of the JPEG 2000 compressed image data.
DCTs are widely used for encoding, decoding, video coding, audio coding, multiplexing, control signals, signaling, analog-to-digital conversion, formatting luminance and color differences, and color formats such as YUV444 and YUV411.
This revolutionary diagnostic technique earned Hounsfield and physicist Allan Cormack the Nobel Prize in Physiology or Medicine in 1979.
As of 2015[update], annual shipments of medical imaging chips reached 46 million units, generating a market value of $1.1 billion.
[43][44] Digital image processing allows the use of much more complex algorithms, and hence, can offer both more sophisticated performance at simple tasks, and the implementation of methods which would be impossible by analogue means.
This allows the coordinate vector to be multiplied by a 3×3 matrix, enabling translation shifts.
These three affine transformations can be combined into a single matrix—thus allowing rotation around any point in the image.
MM operations, such as opening and closing, are composite processes that utilize both dilation and erosion to modify the structure of an image.
For example, applying opening to an image I' with a structuring element B would first reduce small details (through erosion) and then restore the main shapes (through dilation).
This ensures that unwanted noise is removed without significantly altering the size or shape of larger objects.
Both opening and closing can be visualized as ways of refining the structure of an image: opening simplifies and removes small, unnecessary details, while closing consolidates and connects objects to form more cohesive structures.
Additional post processing techniques increase edge sharpness or color saturation to create more naturally looking images.
Westworld (1973) was the first feature film to use the digital image processing to pixellate photography to simulate an android's point of view.
[48] Image processing is also vastly used to produce the chroma key effect that replaces the background of actors with natural or artistic scenery.
Face detection can be implemented with mathematical morphology, the discrete cosine transform (DCT), and horizontal projection.
Process explanation Image quality can be influenced by camera vibration, over-exposure, gray level distribution too centralized, and noise, etc.
