数字图像处理课件(冈萨雷斯第三版)复习材料

(1) 名词解释 RGB Red Green Blue，红绿蓝三原色 CMYK Cyan Magenta yellow blacK , 用于印刷的四分色 HIS Horizontal Situation Indicator 水平位置指示器 FFT Fast Fourier Transform Algorithm (method) 快速傅氏变换算法 CWT continuous wavelet transform 连续小波变换 DCT Discrete Cosine Transform 离散余弦变换 DWT DiscreteWaveletTransform 离散小波变换 CCD Charge Coupled Device 电荷耦合装置 Pixel: a digital image is composed of a finite number of elements,each of which has a particular lication and value,these elements are called pixel 像素 DC component in frequency domain 频域直流分量 GLH Gray Level Histogram 灰度直方图 Mather(basic)wavelet：a function (wave) used to generate a set of wavelets, 母小波，用于产生小波变换所需的一序列子小波 Basis functions basis image 基函数基图像 Multi-scale analysis 多尺度分析 Gaussian function 高斯函数 sharpening filter 锐化滤波器 Smoothing filter/convolution 平滑滤波器/卷积 Image enhancement /image restoration 图像增强和图像恢复

（2）问答题 1. Cite one example of digital image processing Answer: In the domain of medical image processing we may need to inspect a certain class of images generated by an electron microscope to eliminate bright, isolated dots that are no interest.

2.Cite one example of frequency domain operation from the following processing result, make a general comment about ideal highpass filter (figure B) and Gaussian highpass filter(figure D) A. Original image B. ideal highpass filter In contrast to the ideal low pass filter, it is to let all the signals above the cutoff frequency fc without loss, and to make all the signals below the cutoff frequency of FC without loss of. C. the result of ideal highpass filter D. Gaussian highpass filter High pass filter, also known as "low resistance filter", it is an inhibitory spectrum of the low frequency signal and retain high frequency signal model (or device). High pass filter can make the high frequency components, while the high-frequency part of the frequency in the image of the sharp change in the gray area, which is often the edge of the object. So high pass filter can make the image get sharpening processing E. The result of Gaussian filter 3.The original image, the ideal lowpass filter and Gaussian lowpass filter are shown below B nd C .D and E are the result of the either filter B or C A. Draw lines to connect the filter with their result B. Explain the difference of the two filters Due to excessive characteristics of the ideal low-pass filter too fast Jun, it will produce a ringing phenomenon.Over characteristics of Gauss filter is very flat, so it is not ringing

4.What is the result when applying an averaging mask with the size 1X1? 5.State the concept of the Nyquist sampling theorem from the figure belovy The law of sampling process should be followed, also called the sampling theorem and the sampling theorem. The sampling theorem shows the relationship between the sampling frequency and the signal spectrum, and it is the basic basis of the continuous signal discretization. In analog / digital signal conversion process, when the sampling frequency fs.max greater than 2 times the highest frequency present in the signal Fmax fs.max>2fmax, sampling digital signal completely retained the information in the original signal, the general practical application assurance sampling frequency is 5 ~ 10 times higher than that of the signal of the high frequency; sampling theorem, also known as the Nyquist theorem

6.A mean filter is a linear filter but a median filter is not, why? Mean filter is a typical linear filtering algorithm, it is to point to in the target pixels in the image to a template, this template including its surrounding adjacent pixels and the pixels in itself.To use in the template to replace all the pixels of average pixel values.Linear filter, median filter, also known as the main method used in the bounded domain average method. Median filter is a kind of commonly used nonlinear smoothing filter and its basic principle is to put the little value in a digital image or sequence to use value at various points in the field of a point at which the value to replace, its main function is to let the surrounding pixel gray value differences between larger pixel change with the surrounding pixels value close to the values, which can eliminate the noise of the isolated points, so median filter to filter out the salt and pepper noise image is very effective.

（3）算法题 1.The following matrix A is a 3*3 image and B is 3*3 Laplacian mask, what will be the resulting image? (Note that the elements beyond the border remain unchanged)