MATLAB denoise, will MATLAB median filtering be lower after denoising than before denoising?

1.Read the image.

2.Do FFT

3.FFT is displayed

4.Observe the noise in the spectrum with the naked eye. (Sinusoidal interference is a few points in the spectrum)5The area with noise in the spectrum is set to 0(or low-pass) 6Inverse FFT transformation.

7.Display. 1.Read the image.

im=imread('File name');

2.Do FFT

im fft=(fftshift(fft2(im)))fftshift is to put the low-frequency component in the middle, which is customary to do.

3.FFT is displayed

im_magfft=abs(im_fft);

temp1=log(im_magfft+1);% otherwise the amplitude is too large to show the full dynamic range.

xmin = min(min(temp1));

xmax = max(max(temp1));

scaf = 255/(xmax-xmin);

im_ftd = floor(scaf*(temp1 - xmin));

figure;

imshow(im_ftd);

4.Observe the noise in the spectrum with the naked eye. (Sinusoidal interference is a few points in the spectrum)5The area with noise in the spectrum is set to 0(or low-pass) is an example of low-pass.

r = 70;% of the center radius of the low pass, observe for yourself.

for i=1:m

for j=1:n

if ((i-m/2)^2+(j-n/2)^2) elsemask(i,j) = 0;

endend

endim2_fft=im_fft.*mask;

6.Inverse FFT transformation.

im2=ifft(ishiftfft(im2_fft));

7.Display. imshow(im2);

I have a book to pass on to you.

Summary. Hello, glad your question, not necessarily, depends on the type and intensity of the noise. The purpose of denoising in the value filtering method is to replace the noise in the image with the average value of the adjacent pixels in order to reduce the noise in the image and thus improve the image quality.

However, if the noise is too strong, then the denoised image may be blurry than the image before the denoise.

Hello, glad your question, not necessarily, depends on the type and intensity of the noise. The purpose of denoising in the value filter method is to replace the noise in the image with the average value of the adjacent pixels, masking the leakage to reduce the noise in the image, thereby improving the image quality. However, if the noise is too strong and the macro segment is bad, the denoised image may be blurry than the image before the denoise.

Fellow, I really didn't understand, I can be more specific.

Hello, to put it simply, the MATLAB median filter method is lower after denoising than before denoising, which means that the noise is suppressed, but at the same time, useful information is suppressed, making the overall signal weaker. This is because the value filter works: it changes the value of each pixel to the median of the pixels around it, which means that the noise is suppressed, but the useful information is also suppressed, because their pixel value may be changed.

Hello dear MATLAB median filtering method will be lower after denoising than before denoising. Noise is an important cause of image interference. There may be a variety of noise in the actual application of an image, which may be generated during transmission or in processing such as quantization.

According to the relationship between noise and signal, it can be divided into three forms: (f(x,y) represents the given original image, g(x,y) represents the image signal, and n(x,y) represents the noise. 1) Additive noise, this kind of noise has nothing to do with the input image letter difference line number, the noisy image can be expressed as f(x,y)=g(x,y) + n(x,y), channel noise and noise generated by the camera scanning image of the light guide camera tube belong to this kind of noise.

2) Multiplicative noise, this kind of noise is related to the image signal, the noisy image banquet can be expressed as f(x,y)=g(x,y)+ n(x,y)g(x,y), the noise when the flying point scanner carries the image, the coherent noise in the TV image, and the particle noise in the film belong to this kind of noise. 3) Quantization noise, this kind of noise has nothing to do with the input image signal, it is the quantization error in the quantization process, and then it is reflected to the receiving end and generated.

(1)j = imnoise(i,type);

2)j = imnoise(i,type,parameters);

where i is the gray matrix of the original image, and j is the gray matrix of the image after adding noise.

In general, it is sufficient to use (1) to indicate that the parameters are allowed to be modified, and (1) to use the default parameters;

As for type, there can be five types, namely:'gaussian'(Gaussian white noise),'localvar'(zero-mean Gaussian white noise in relation to the grayscale value of the image),'poisson'(Poisson noise),'salt & pepper'(salt and pepper noise) and'speckle'(speckle noise); The setting of the parameter value in specific (2) can be based on personal needs; For the rest of the situation and if you still don't understand, please refer to the MATLAB help file.

Use here'salt & pepper'(Salt and Pepper Noise) and set its parameter to. Examples of this are as follows:

l = imread(‘image_;

j = imnoise(l, ‘salt & pepper’,

imshow(j);An immediate pop-up window shows the added noise.

Stored at 100% quality with added noise, the default value of quality is 75

The above program means adding salt and pepper noise to the original image, but be careful to put the image in the same subdirectory as the m file of the above program.

How to learn VB well

One. What is VB?

VB is Visual

Basic programming language.

Writing a computer program requires the use of a computer programming language. Computer programming languages are the bridge between humans and computers. Just like human languages, there are many computer programming languages.

At present, the most widely used languages are "C++", "Pascal", "Basic", etc. Among the many computer programming languages, the basic language is the easiest to learn and use.

Basic is English for Beginner's

allpurpose

symbolic

instruction

The abbreviation of code, which means universal symbol instruction for beginners**, has always been the language of choice for beginner programming applications.

Two. What is the use of learning VB?

VB can do a lot of things, whenever you want to.

Application. Database program. As long as you can think of it, you can basically do it.

However, large and complex programming such as operating systems is now generally programmed in C. It's hard to do with VB. If you want to be a programmer, you can't just know VB.

It's better to learn a little bit more. For example, an asp database. net。

That's how we make better things.

Three. How to learn VB well

VB is an easy-to-learn language, which is typically easy to get started and hard to master.

Today, VB is still the most widely spoken language in the world. The more suitable field is the MIS of the C S architecture, and the derived language VBSict is a very suitable language for the B S architecture MIS, etc., and its simplicity and easy modification are very suitable for the situation of changing management system requirements. The support for the database is also very good, there is MS support in the back, what are you worried about, but any language is evolving, VB is no exception, LZ can be learned on the basis of the present.

.NET architecture, to meet the needs of development.

If you're not a coincidence, I can introduce a way to learn:

1.Read the book first, and have a general understanding of some basic things, no"A blind man touches an elephant"

2.Learn from small things (it's all about practice), e.g. VB

Trigonometric functions. Clock. I think there will be in the book. You can also check out the tutorials on the web.

3.A very important piece of advice: when you have already seen results, it is better to go to a VB advanced tuition school. To use an analogy: if you practice the best, you have to have someone to help you open up the meridians.

4.Suggested books:

1) "Learn Programming by Example--Visual

Basic Programming

Xidian University Press.

2) VB programming tutorial edited by Cao Qing, Qiu Lihua and Guo Zhiqiang published by Machinery Industry Press.