Lecture
Digital image processing, or the acquisition of digital images, is the creation of a digital representation of the visual characteristics of an object, such as a physical scene or the internal structure of an object. The term often implies or includes the processing, compression, storage, printing, and display of such images. A key advantage of a digital image over an analog image, such as a film photograph, is the ability to make digital copies of the original object an unlimited number of times without any loss of image quality.
Digital images can be classified by the type of electromagnetic radiation or other waves whose variable attenuation as it passes through objects, or reflects off them, conveys the information that makes up the image. In all classes of digital images, the information is converted by image sensors into digital signals, which are processed by a computer and output as an image in visible light. For example, the visible-light medium enables digital photography (including digital videography) using various kinds of digital cameras (including digital video cameras). X-rays enable digital X-ray imaging (digital radiography, fluoroscopy, and CT), while gamma rays enable digital gamma imaging (digital scintigraphy, SPECT, and PET). Sound enables ultrasonography (for example, medical ultrasound examination) and sonar, while radio waves enable radar. Digital images lend themselves well to image analysis using software, as well as to image editing (including image manipulation).
Before the advent of digital imaging, the first photograph, «View from the Window at Le Gras», was taken in 1826 by the Frenchman Joseph Nicéphore Niépce. When Joseph was 28 years old, he discussed with his brother Claude the possibility of reproducing images using light. His attention to new innovations began in 1816. In fact, he was more interested in building an engine for a boat. Joseph and his brother worked on this for quite a long time, and Claude successfully promoted his innovations, moving abroad and promoting them in England. Joseph was able to focus on photography, and finally in 1826 he managed to take his first photograph of a view from a window. It required an exposure of 8 hours or more.
The first digital image was obtained in 1920 by the Bartlane cable picture transmission system. British inventors Harry G. Bartholomew and Maynard D. McFarlane developed this method. The process consisted of «a series of negatives on zinc plates that were exposed for varying lengths of time, thus creating different densities». The Bartlane cable picture transmission system generated, at both the transmitting and receiving ends, a perforated data card or tape that was then reproduced as an image.
In 1957, Russell A. Kirsch created a device that generated digital data which could be stored on a computer; it used a drum scanner and a photomultiplier tube.
Digital image processing was developed in the 1960s and 1970s, mainly to avoid the operational drawbacks of film cameras, for scientific and military missions, including the KH-11 program. As digital technology became cheaper in the following decades, it replaced older film-based methods for many purposes.
In the early 1960s, while developing compact, lightweight, portable equipment for airborne nondestructive testing of naval aircraft, Frederick G. Weighart and James F. McNulty (an American radio engineer) at Automation Industries, Inc., then in El Segundo, California, jointly invented the first apparatus for generating a real-time digital image, which took the form of a fluoroscopic digital radiograph. Rectangular-wave signals were detected to form the image on the fluoroscope's fluorescent screen.
The charge-coupled device was invented by Willard S. Boyle and George E. Smith at Bell Labs in 1969. While researching MOS technology, they realized that electrical charge was analogous to a magnetic bubble and could be stored on a tiny MOS capacitor. Since it was fairly simple to fabricate a row of MOS capacitors in sequence, they connected a suitable voltage to them so that the charge could be transferred from one to the next. The CCD is a semiconductor circuit that was later used in the first digital video cameras for television broadcasting.
Early CCD sensors suffered from shutter lag. This problem was largely resolved with the invention of the pinned photodiode (PPD). It was invented by Nobukazu Teranishi, Hiromitsu Shiraki, and Yasuo Ishihara at NEC in 1980. It was a photodetector structure with low lag, low noise, high quantum efficiency, and low dark current. In 1987, PPDs began to be incorporated into most CCD devices, becoming an integral part of consumer electronic video cameras and later digital cameras. Since then, PPDs have been used in nearly all CCD sensors and later in CMOS sensors as well.
The NMOS active-pixel sensor (APS) was invented by Olympus in Japan in the mid-1980s. This was made possible by advances in MOS semiconductor device fabrication, as MOSFET scaling reached micron and then submicron levels. The NMOS active-pixel sensor was fabricated by Tsutomu Nakamura's team at Olympus in 1985. The CMOS active-pixel sensor (CMOS sensor) was later developed by Eric Fossum's team at NASA's Jet Propulsion Laboratory in 1993. By 2007, sales of CMOS sensors had surpassed those of CCD sensors.
An important advance in digital image compression technology was the discrete cosine transform (DCT). DCT compression is used in JPEG, which was introduced by the Joint Photographic Experts Group in 1992. JPEG compresses images to much smaller file sizes and has become the most widely used image file format on the Internet.
These various scanning ideas formed the basis for the first digital camera designs. Early cameras took a long time to capture an image and were poorly suited for consumer purposes. It was only with the adoption of the CCD (charge-coupled device) that digital cameras truly became popular. The CCD became part of the imaging systems used in telescopes and the first black-and-white digital cameras in the 1980s. Color was eventually added to the CCD, and today it is a standard camera feature.
Great strides have been made in the field of digital image processing. Negatives and exposure are alien concepts to many, and the first digital image in 1920 eventually led to cheaper equipment, increasingly powerful yet simple software, and the growth of the Internet.
The continuous development and production of physical equipment and hardware related to digital image processing has affected the environment in this field. From cameras and webcams to printers and scanners, hardware is becoming sleeker, thinner, faster, and cheaper. As the cost of equipment decreases, the market expands for new enthusiasts, allowing more consumers to experience the thrill of creating their own images.
Everyday personal laptops, family desktop computers, and corporate computers are capable of running photographic software. Our computers are more powerful machines with growing capabilities for running any type of program, especially digital image processing software. And this software is quickly becoming both smarter and simpler. Although the features of modern programs reach the level of precise editing and even 3D image rendering, user interfaces are designed to be convenient for both advanced users and beginners.
The Internet makes it possible to edit, view, and share digital photographs and graphics. A quick browse of web pages can easily reveal the graphic works of budding artists, news photographs from around the world, corporate images of new products and services, and much more. The Internet has clearly proven to be a catalyst in fostering the growth of digital image processing.
Online photo sharing is changing our understanding of photography and photographers. Online sites such as Flickr, Shutterfly, and Instagram give billions of people the ability to share their photographs, whether amateur or professional. Photography has evolved from a luxurious medium of communication and sharing into something more than a fleeting moment in time. Subjects have also changed. In the past, photographs mostly depicted people and family. Now we photograph anything. We can capture our day and share it with everyone with a single touch of our fingers.
In 1826, Niépce was the first to develop photography, using light to reproduce images, and the progress of photography has increased dramatically over the years. Now everyone is a photographer in their own way, whereas in the early 1800s and 1900s the value of durable photographs was highly prized and valued by both consumers and producers. According to a magazine article on five ways the digital camera has changed us, the following is stated: The impact on professional photographers has been dramatic. Once, a photographer would not dare to waste a frame unless nearly certain it would work. The use of digital image processing (photography) has changed the way we interact with our environment over the years. Part of the world is perceived differently through the visual representation of lasting memories; this has become a new form of communication with friends, family, and loved ones around the world without personal interaction. With photography, it is easy to see those you have never seen before and to feel their presence without them being nearby — for example, Instagram is a form of social media where anyone can take, edit, and share photos of whatever they want with friends and family. Facebook, Snapchat, Vine, and Twitter are also ways in which people express themselves with few or no words and can capture every important moment. Preserving lasting memories, which used to be difficult, is now easy, because now anyone can take pictures and edit them on their phones or laptops. Photography has become a new means of communication, and over time it is growing rapidly, which has affected the world around us.
A study conducted by Basey, Maines, Francis, and Melbourne found that drawings used in the classroom have a significant negative effect on lower-order content in students' lab reports, lab perspectives, excitement, and time-on-task efficiency. Documentation-style instruction had no significant effect on students in these areas. It also found that students were more motivated and enthusiastic about learning when digital images were used.
In education.
The field of medical imaging
In the field of technology, digital image processing has become more useful than analog image processing, considering modern technological progress.
Digital image processing for augmented reality (DIAR) is a comprehensive field within the broader context of augmented reality (AR) technology. It involves the creation, processing, and interpretation of digital images for use in augmented reality environments. DIAR plays an important role in improving the user experience by providing realistic overlays of digital information on the real world, thereby bridging the gap between the physical and virtual worlds.
DIAR is used in many sectors, including entertainment, education, healthcare, the military, and retail. In entertainment, DIAR is used to create immersive gaming experiences and interactive films. In education, it provides a more engaging learning environment, and in healthcare it assists with complex surgical procedures. The military uses DIAR for training purposes and battlefield visualization. In retail, customers can virtually try on clothing or visualize furniture in their homes before making a purchase.
With the continuous development of technology, the future of DIAR is expected to see more realistic overlays, improved 3D object modeling, and seamless integration with the Internet of Things (IoT). Incorporating haptic feedback into DIAR systems could further enhance the user experience by adding a sense of touch to visual overlays. In addition, advances in artificial intelligence and machine learning are expected to further improve context-appropriate and realistic overlaid digital images.
Although theories are rapidly becoming reality in modern technological society, the range of possibilities for digital image processing remains wide open. One major application still under development is child safety and protection. How can we use digital images to better protect our children? The Kodak Kids Identification Digital Software (KIDS) program may answer this question. Its beginnings include a digital imaging kit that would be used to compile photographs for student identification cards, which would be useful during emergencies and crimes. More powerful and advanced versions of such applications are still being developed, with improved features constantly being tested and added.
But parents and schools are not the only ones who see the benefit of such databases. Criminal investigation agencies, such as police departments, state forensic laboratories, and even federal bureaus, have recognized the importance of digital imaging for analyzing fingerprints and evidence, making arrests, and maintaining community safety. As the field of digital imaging develops, so too do our capabilities for protecting the public.
Digital imaging can be closely linked to social presence theory, especially when it comes to the social-media aspect of photos taken with our phones. There are many different definitions of social presence theory, but two of them clearly define what it is: «the degree to which people are perceived as real» (Gunawardena, 1995) and «the ability to project oneself socially and emotionally as real people» (Garrison, 2000). Digital imaging allows a person to express their social life through images, giving a sense of their presence to the virtual world. The presence of these images acts as an extension of the self to others, giving a digital representation of what they are doing and who they are with. Digital imaging, in the sense of cameras on phones, helps facilitate this effect of presence with friends on social media. Alexander (2012) states: «presence and representation are deeply embedded in our reflections on images... this is, of course, an altered presence... no one confuses the image with the reality it represents. But we allow ourselves to be captivated by this representation, and only this "representation" is capable of plausibly showing the vividness of the absent». Thus, the digital image allows us to be represented in a way that reflects our social presence.
Photography is a medium used to visually capture particular moments. Thanks to photography, our culture has gained the ability to convey information (such as appearance) with little or no distortion. Media richness theory provides a framework for describing a medium's ability to convey information without loss or distortion. This theory has provided a way to understand human behavior in communication technologies. In an article written by Daft and Lengel (1984, 1986), the following is stated:
Communication media fall along a continuum of richness. The richness of a medium includes four aspects: the availability of immediate feedback, which allows questions to be asked and answered; the use of multiple cues, such as physical presence, tone of voice, body gestures, words, numbers, and graphic symbols; the use of natural language, which can be used to convey understanding of a wide range of concepts and ideas; and the personal focus of the medium (p. 83).
The more a medium is able to convey accurate appearance, social cues, and other similar characteristics, the richer it becomes. Photography has become a natural part of how we communicate. For example, most phones have the ability to send photos in text messages. Snapchat and Vine apps are becoming increasingly popular for communication. Sites such as Instagram and Facebook have also allowed users to achieve a deeper level of richness thanks to their ability to convey information. Shea, V. C. (January–March 2011). Adolescents' use of MSN features, discussion topics, and the development of online friendships: the influence of media richness and communication control. Communication Quarterly, 59(1).
A digital photograph can be created directly from a physical scene using a camera or similar device. Alternatively, a digital image can be obtained from another image on an analog medium, such as photographs, photographic film, or printed paper, using an image scanner or similar device. Many technical images, such as those obtained using tomographic equipment, side-scan sonar, or radio telescopes, are actually obtained through complex processing of non-image data. Weather radar maps, which can be seen on television news, are a common example. The digitization of real-world analog data is known as digitization and involves sampling (discretization) and quantization. A projection image for digital radiography can be made using X-ray detectors that convert the image directly into digital format. Alternatively, phosphor-plate radiography involves capturing the image first on a photostimulable phosphor (PSP) plate, which is then scanned using a mechanism called photostimulated luminescence.
Finally, a digital image can also be computed from a geometric model or a mathematical formula. In this case, the term image synthesis is more appropriate, and it is more commonly referred to as rendering.
The authentication of digital images is a challenge for providers and producers of digital images, such as healthcare organizations, law enforcement agencies, and insurance companies. In forensic photography, methods are emerging for analyzing digital images and determining whether they have been altered.
In the past, digital image processing depended on chemical and mechanical processes; now all of these processes have moved into the electronic realm. For digital image processing to take place, several steps are required: light energy is converted into electrical energy — imagine a grid with millions of tiny solar cells. Each condition generates a specific electrical charge. The charges from each of these "solar cells" are transported and transmitted to firmware for interpretation. Firmware is what understands and translates color and other qualities of light. Pixels are what is noticed next; with varying intensity they create and produce different colors, forming a picture or image. Finally, the firmware records the information for future reference and for reproduction.
Digital image processing has several advantages. First, this process provides easy access to photographs and text documents. Google is at the forefront of this «revolution», with its mission to digitize the world's books. Such digitization will make books searchable, thereby making participating libraries, such as Stanford University and the University of California, Berkeley, accessible worldwide. Digital image processing also benefits the medical world, as it «allows for the electronic transmission of images to third-party providers, referring dentists, consultants, and insurers via modem». This process «is also environmentally friendly, since it does not require chemical processing». Digital image processing is also often used to document and record historical, scientific, and personal events.
Advantages also exist with respect to photographs. Digital image processing will reduce the need for physical contact with original images. In addition, digital image processing creates the possibility of reconstructing the visual content of partially damaged photographs, thereby eliminating the risk that the original will be altered or destroyed. Furthermore, photographers will be «freed from being "chained" to the darkroom», will have more time for shooting, and will be able to complete assignments more efficiently. Digital image processing «means» that «photographers no longer need to rush to deliver film to the office, so they can stay longer on location while still meeting deadlines».
Another advantage of digital photography is that it has spread to camera phones. We can take cameras with us anywhere, as well as instantly send photos to others. This is easy for people and also helps with the process of self-identification for the younger generation.
Critics of digital image processing point to several negative consequences. Increased «flexibility in providing readers with higher-quality images» will tempt editors, photographers, and journalists to manipulate photographs. In addition, «staff photographers will no longer be photojournalists, but camera operators... since editors have the right to decide what they want to "shoot"».
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