APS 审核复习digital image processing

Digital image processing is the use of computer algorithms算法to perform image processing on digital images. As a subcategory子种类or field of digital signal processing, digital image processing has many advantages over analog image模拟图像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 signal distortion变形失真during processing. Since images are defined over two dimensions 二维(perhaps more) digital image processing may be modeled in the form of multidimensional systems.
A digital image processing allows the use of much more complex algorithms for image processing, and hence因此, can offer both more sophisticated复杂的performance at simple tasks, and the implementation of methods which would be impossible by analog means.
Applications
Digital camera images
Digital cameras generally include dedicated专用的digital image processing chips to convert转换the raw data原始数据from the image sensor图像传感器into a color-corrected image in a standard image标准图像file format文件格式. Images from digital cameras often receive further processing to improve their quality, a distinct独特的明显的advantage that digital cameras have over film cameras. The digital image processing typically is executed by special software programs that can manipulate the images in many ways.
Intelligent transportation systems
Digital image processing has a wide applications in intelligent transportation systems智能交通系统, such as automatic number plate recognition自动车牌识别and traffic sign recognition交通标志识别.
digital image acquisition图像获取
Digital imaging or digital image acquisition is the creation of digital images, typically from a physical scene场景. The term is often assumed to imply or include the processing, compression, storage, printing, and display of such images. The most usual method is by digital photography with a digital camera but other methods are also employed.
Digital imaging was developed in the 1960s and 1970s, largely to avoid the operational weaknesses of film cameras, for scientific and military missions including the KH-11 program. As digital technology became cheaper in later decades it replaced the old film methods for many purposes.
Methods
A digital photograph may be created directly from a physical scene by a camera or similar device. Alternatively, a digital image may be obtained from another image in an analog medium, such as photographs, photographic film, or printed
paper, by an image scanner or similar device.Many technical images—such as those acquired with tomographic equipment, side-scan sonar, or radio tele scopes—are actually obtained by complex processing of non-image data. Weather radar maps as seen on television news are a commonplace example. The digitalization of analog real-world data is known as digitizing, and involves sampling (discretization) and quantization.
Finally, a digital image can also be computed from a geometric model or mathematical formula. In this case the name image synthesis is more appropriate, and it is more often known as rendering.
Digital image authentication is an issue for the providers and producers of digital images such as health care organizations, law enforcement agencies and insurance companies. There are methods emerging in forensic photography to analyze a digital image and determine if it has been altered.
image enhancement
Camera or computer image editing programs often offer basic automatic image enhancement features that correct color hue and brightness imbalances as well as other image editing features, such as red eye removal, sharpness adjustments, zoom features and automatic cropping. These are called automatic because generally they happen without user interaction or are offered with one click of a button or mouse button or by selecting an option from a menu. Additionally, some automatic editing features offer a combination of editing actions with little or no user interaction. Image restoration
Image restoration is the operation of taking a corrupted/noisy image and estimating the clean original image. Corruption may come in many forms such as motion blur, noise, and camera misfocus
image coding or Digital data compression
Many image file formats use data compression to reduce file size and save storage space. Digital compression of images may take place in the camera, or can be done in the computer with the image editor. When images are stored in JPEG format, compression has already taken place. Both cameras and computer programs allow the user to set the level of compression.
Some compression algorithms, such as those used in PNG file format, are lossless, which means no information is lost when the file is saved. By contrast, the JPEG file format uses a lossy compression algorithm by which the greater the compression, the more information is lost, ultimately reducing image quality or detail that can not be restored. JPEG uses knowledge of the way the human brain and eyes perceive color to make this loss of detail less noticeable.。