What Is Fourier Image Processing?

Image processing A technique that uses a computer to analyze an image to achieve the desired result. Also called image processing. Image processing generally refers to digital image processing. Digital image refers to a large two-dimensional array obtained by taking pictures with industrial cameras, video cameras, scanners and other equipment. The elements of the array are called pixels, and their values are called gray values. Image processing technology generally includes three parts: image compression, enhancement and restoration, matching, description and recognition.

The 21st century is an era full of information. As the visual basis of human perception of the world, images are an important means for humans to obtain information, express information, and transmit information. Digital image processing, which uses computers to process images, has a short history of development. Digital image processing technology originated in the 1920s, when a photo was transmitted from London, England, to New York, USA via a submarine cable, using digital

1) Image transformation: Due to the large image array, processing directly in the spatial domain involves a large amount of calculation. Therefore, various image transformation methods, such as indirect processing techniques such as Fourier transform, Walsh transform, and discrete cosine transform, are often used to convert the processing of the spatial domain into the processing of the transform domain, which not only reduces the amount of calculation, but also obtains more effective Processing (such as Fourier transform can be digitally filtered in the frequency domain). At present, the wavelet transform in emerging research has good localization characteristics in both time and frequency domains. It has also been widely and effectively used in image processing.

2) Image coding and compression: Image coding and compression technology can reduce the amount of data describing the image (ie, the number of bits), in order to save image transmission, processing time, and reduce the memory capacity occupied. Compression can be obtained without distortion, or it can be performed with permissible distortion. Coding is the most important method in compression technology. It is the earliest and more mature technology in image processing technology.

3) Image enhancement and restoration: The purpose of image enhancement and restoration is to improve the quality of the image, such as removing noise and improving the sharpness of the image. Image enhancement does not consider the cause of image degradation, highlighting the part of interest in the image. For example, enhancing the high-frequency components of the image can make the outline of the objects in the image clear and the details are obvious; for example, strengthening the low-frequency components can reduce the influence of noise in the image. Image restoration requires a certain understanding of the causes of image degradation. Generally speaking, a "degradation model" should be established according to the degradation process, and then some filtering method should be used to restore or reconstruct the original image.

4) Image segmentation: Image segmentation is one of the key technologies in digital image processing. Image segmentation is the extraction of meaningful features in an image. The meaningful features include edges and regions in the image. This is the basis for further image recognition, analysis, and understanding. Although many methods for edge extraction and region segmentation have been developed, there is no effective method that is generally applicable to various images. Therefore, the research on image segmentation is still deepening, and it is one of the research hotspots in image processing.

5) Image description: Image description is a necessary prerequisite for image recognition and understanding. As the simplest binary image, its geometric characteristics can be used to describe the characteristics of the object. The general image description method uses two-dimensional shape description. It has two types of methods: boundary description and area description. For special texture images, two-dimensional texture features can be used. With the further development of image processing research, research on three-dimensional object description has begun, and methods such as volume description, surface description, and generalized cylinder description have been proposed.

6) Image classification (recognition): Image classification (recognition) belongs to the category of pattern recognition. Its main content is that after certain preprocessing (enhancement, restoration, compression) of the image, image segmentation and feature extraction are performed to perform decision classification. Image classification often uses classic pattern recognition methods, including statistical pattern classification and syntactic (structural) pattern classification. Fuzzy pattern recognition and artificial neural network pattern classification, which have been newly developed in recent years, have also received increasing attention in image recognition.

Image processing is inseparable from massive and abundant basic data, including multiple formats such as video and still images, such as Berkeley Segmentation Dataset and Benchmark 500 (BSDS500), Simon Fraser University's image database for different light objects, and neural network face recognition data , CBCL-MIT StreetScenes (MIT Street View Database), etc.

Sampling and quantification process

Encode image information to meet transmission and storage requirements. Encoding can compress the amount of information in an image, but the image quality is almost unchanged. For this reason, analog processing technology can be used, and then the code is obtained through analog-digital conversion, but most of them use digital coding technology. The encoding method includes a method of processing an image point by point, and a method of applying some transformation to the image or encoding based on a region or a feature. Pulse code modulation, differential pulse code modulation, prediction code, and various transformations are common coding techniques.

The data volume of an image obtained by digitization is huge. A typical digital image usually consists of 500 × 500 or 1000 × 1000 pixels. If it is a moving image, the amount of data is larger. Therefore, image compression is necessary for image storage and transmission.

There are two types of compression algorithms for image compression, namely lossless compression and lossy compression. The most commonly used lossless compression algorithm takes the difference between neighboring pixel values in space or time, and then encodes it. Run-length codes are examples of such compressed codes. Most of the lossy compression algorithms use image exchange methods, such as fast Fourier transform or discrete cosine transform of the image. Both JPEG and MPEG, which have become international standards for image compression, are lossy compression algorithms. The former is used for still images and the latter is used for dynamic images. They are all implemented by chips ^[2]

The goal of image enhancement is to improve the quality of the picture, such as increasing contrast, removing blur and noise, and correcting geometric distortion. Image restoration is a technique that attempts to estimate the original image when a model of known blur or noise is assumed.

Image enhancement can be divided into frequency domain method and space domain method according to the method used. The former regards the image as a two-dimensional signal, and performs signal enhancement based on the two-dimensional Fourier transform. Using low-pass filtering (that is, passing only low-frequency signals) can remove noise in the picture; using high-pass filtering can enhance high-frequency signals such as edges, and make blurred pictures clear. Representative spatial domain algorithms include local averaging and

The term morphology usually refers to a branch of biology that deals with the shapes and structures of animals and plants. This term is also used in the context of mathematical morphology as a tool for extracting image components that are useful in representing and describing the shape of regions such as boundaries, bones, and convex hulls. In addition, we also pay attention to morphological techniques for pre- and post-processing, such as morphological filtering, thinning, and cropping.

Basic operations of mathematical morphology

There are four basic operations in mathematical morphology: corrosion, swelling, opening and closing. The mathematical morphology method uses a "probe" called a structural element to collect image information. When the probe is constantly moving in the image, it can examine the correlation between the various parts of the image to understand the structural characteristics of the image. In continuous space, the corrosion, expansion, opening, and closing operations of grayscale images are expressed as follows.

corrosion

Erodes objects in a "shrink" or "refine" binary image. The way and degree of shrinkage is controlled by a structural element. Mathematically, A is corroded by B, denoted as AB, and defined as:

In other words

Extract some useful metrics, data, or information from the image. The goal is to get some numerical result, not to produce another image. Content of image analysis and

Photography and Printing

Satellite image processing

Medical image processing

Face recognition, feature detection, face identification

Microscope image processing

Car barrier detection ^[6]

Adobe Photoshop

Software features: image processing software with the highest visibility and usage.

Software advantages: Use industry-standard Adobe PhotoshopCS software to get better results faster, while providing essential new features for graphic and web design, photography, and video.

Comparison with counterpart software: This time Adobe did give designers a lot of surprises. Photoshop CS has added many powerful features, especially for photographers. This time it has greatly broken through the previous Photoshop series. The product pays more attention to the limitations of graphic design, and has greatly enhanced and broken the support function of digital darkroom.

Recent version: On November 2, 2016, Adobe Corporation updated its latest version of Photoshop CC 2017. ^[7]

Adobe Illustrator

Software features : Professional vector drawing tools, powerful and friendly interface.

Software advantages: Whether you are a designer and professional illustrator producing print and publishing line art, an artist producing multimedia images, or a producer of Internet pages or online content, you will find that Illustrator is more than just an art product tool, suitable for most From small designs to large complex projects.

Comparison with peer software : extremely powerful and professional. Compatible with other Adobe software such as Photoshop, Primiere and Indesign, which has obvious advantages in the professional field.

CorelDRAW

Software features: Friendly interface design, wide space and delicate operation. Good compatibility.

Software advantages: extraordinary design capabilities are widely used in trademark design, logo production, model drawing, illustration drawing, typesetting and color separation output and many other fields. Market-leading file compatibility and high-quality content can help you turn your ideas into professional work. From distinctive logos and signs to eye-catching marketing materials and pleasing web graphics.

Comparison with peer software : powerful, excellent compatibility, can generate a variety of formats compatible with other software, simpler operation than Illustrator, the application rate is very high in domestic small and medium advertising design companies.

Cow image

Software features: Keniu Image is a new generation of image processing software. It has unique functions such as whitening and removing acne, face-lifting, star scene, and multiple photo overlays. It also has more than 50 kinds of photo effects, which can produce studio-level professional photos in seconds .

Software advantages: picture editing, portrait beauty, scene calendar, adding watermark jewelry, adding various artistic fonts, making dynamic flashing pictures, moving head dolls, multi-picture stitching, the functions that make people think of, have everything, and easy to use.

Comparison with counterpart software: scene calendar, dynamic flash, moving head doll, etc. are not found in traditional image processing software. With Keniu Image, you no longer need professional skills to process photos like Photoshop.

Shadow magic hands

Software Features: "nEO iMAGING" is a software for improving the quality of digital photos and processing effects. Simple and easy to use, you don't need any professional image technology to produce color effects for professional film photography.

Software advantages: Simulate the effect of reversal film, make the photo contrast more vivid, the color is more beautiful, simulate the effect of reverse negative impact, the colors are strange and novel, simulate the effects of many types of black and white film, in contrast, contrast, and digital photos completely different.

Comparison with counterpart software: it is a software for improving the quality of photos and personalizing it. Simple and easy to use, everyone can make beautiful photo frames, art photos, professional film effects, and it's completely free.

ACDSee

Software features: No matter what type of photos you take-family and friends, or artistic photos taken as a hobby-you need photo management software to easily and quickly organize and view, correct and share these photos.

Software advantages: ACDSee 9 can quickly "get photos" from any storage device, and can also use password-protected "Privacy Folder" as a new feature to store confidential information.

Comparison with peer software: powerful email options, slideshows, CD / DVD burning, and web album tools that make sharing photos a breeze. Improve your photos with quick fixes like red-eye removal, color cast removal, exposure adjustment, and the Photo Fix tool.

Macromedia Flash

Software features: A visual web design and website management tool that supports the latest web technologies, including HTML inspection, HTML format control, HTML formatting options, and more.

Software advantages: In addition to new video and animation features, it also provides new drawing effects and better scripting support. It also integrates popular video editing and encoding tools. It also provides software that allows users to test Flash content on mobile phones. new function.

Comparison with peer software: In editing, you can choose the visualization method or the source code editing method you like.

Ulead GIF Animator

Software features: Animated GIF production software published by Ulead. Built-in Plugin has many ready-made special effects that can be applied immediately. It can convert AVI files into animated GIF files, and it can also optimize animated GIF pictures. Animated GIF files placed on the web page to lose weight, so that people can browse the web faster.

Software advantages: This is a very convenient GIF animation software, created by Ulead Systems.Inc. Ulead GIF Animator can not only save a series of pictures in an animated GIF format, but also produce more than twenty 2D or 3D dynamic effects, which is enough to meet your requirements for making web animation.

Comparison with peer software: Unlike other graphic file formats, multiple pictures can be stored in a GIF file. At this time, the GIF displays the pictures stored in turns as a slide show, which forms an animation. ^{[8 ]} .