Common MATLAB Image operations

Original post address: http://blog.verycd.com/ari/showentry=48371

I. Read and Write image files

1 imread

The imread function is used to read various image files, such as a = imread ('e:/w01.tif ')

Note: The corresponding. tif file w01 must be available on the computer's elastic drive.

2 imwrite

The imwrite function is used to write image files, such as imwrite (a, 'e:/w02.tif ', 'tif ')

3 imfinfo

The imfinfo function is used to read information about an image file, for example, imfinfo ('e:/w01.tif ')

2. Image Display

1 image

The image function is the most primitive image display function provided by MATLAB, such:

A = [1, 2, 3, 4; 4, 5, 6, 7; 8, 9, 10, 11, 12];

Image ();

2 imshow

The imshow function is used to display image files, for example:

I = imread ('e:/w01.tif ');

Imshow (I );

3 colorbar

The colorbar function displays the color bar of an image, for example:

I = imread ('e:/w01.tif ');

Imshow (I );

Colorbar;

4. figure

The figure function is used to set the image display window, for example, figure (1);/figure (2 );

Three-image transformation

1 fft2

The fft2 function is used for two-dimensional Fourier transformation of digital images, for example:

I = imread ('e:/w01.tif ');

J = fft2 (I );

2 ifft2

The ifft2 function is used for two-dimensional Fourier inverse transformation of digital images, such:

I = imread ('e:/w01.tif ');

J = fft2 (I );

K = ifft2 (j );

3. Use fft2 to calculate two-dimensional convolution

The fft2 function can be used to calculate two-dimensional convolution, for example:

A = [8, 1, 6; 3, 5, 7; 4, 9, 2];

B = [, 1;, 1;, 1];

A (8, 8) = 0;

B (8, 8) = 0;

C = ifft2 (fft2 (a). * fft2 ();

C = c );

Conv2 (two-dimensional convolution function) is used for verification, for example:

A = [8, 1, 6; 3, 5, 7; 4, 9, 2];

B = [, 1;, 1;, 1];

C = conv2 (,;

Four functions for generating analog noise and predefined Filters

1 imnoise

The imnoise function is used to generate analog noise for an image, for example:

I = imread ('e:/w01.tif ');

J = imnoise (I, 'gaussian ', 0, 0.02); % simulate gaussian Noise

2 fspecial

The fspecial function is used to generate a predefined filter, for example:

H = fspecial ('sobel '); % sobel horizontal edge enhancement Filter

H = fspecial ('gaussian '); % gaussian low-pass filter

H = fspecial ('laplacian '); % Laplace Filter

H = fspecial ('log'); % Gaussian Laplace (log) Filter

H = fspecial ('average'); % Mean Filter

5. Image Enhancement

1 Histogram

The imhist function is used to display the histogram of a digital image, for example:

I = imread ('e:/w01.tif ');

Imhist (I );

2 histogram homogenization

The histeq function is used to normalize the histogram of digital images, for example:

I = imread ('e:/w01.tif ');

J = histeq (I );

3. Contrast Adjustment

The imadjust function is used to adjust the contrast of a digital image, for example:

I = imread ('e:/w01.tif ');

J = imadjust (I, [0.3, 0.7], []);

4 logarithm Transformation

The log function is used to convert the logarithm of a digital image, for example:

I = imread ('e:/w01.tif ');

J = double (I );

K = log (j );

5 Convolution-based image filtering functions

The filter2 function is used for image filtering, for example:

I = imread ('e:/w01.tif ');

H = [, 1;, 0;-1,-2,-1];

J = filter2 (H, I );

6. linear filtering

Use two-dimensional conv2 convolution for filtering, such:

I = imread ('e:/w01.tif ');

H = [, 1;, 1;, 1];

H = H/9;

J = conv2 (I, H );

7. Median Filter

The medfilt2 function is used for image median filtering, for example:

I = imread ('e:/w01.tif ');

J = medfilt2 (I );

8 sharpen

(1) sharpen an image by using the Sobel operator, for example:

I = imread ('e:/w01.tif ');

H = [, 1;, 0;-1,-2,-1]; % Sobel operator

J = filter2 (H, I );

(2) sharpen an image by using the Laplace operator, for example:

I = imread ('e:/w01.tif ');

J = double (I );

H = [, 0; 1,-;, 0]; % LAPLACE OPERATOR

K = conv2 (J, H, 'same ');

M = J-K;

Example 6

Two-dimensional Fourier transformation and two-dimensional Fourier inverse transformation:

I = imread ('e:/w01.tif ');

Figure (1 );

Imshow (I );

Colorbar;

J = fft2 (I );

K = fftshift (j );

Figure (2 );

L = log (abs (k ));

Imshow (l, []);

Colorbar

N = ifft2 (j)/255;

Figure (3 );

Imshow (n );

Colorbar;