This document provides an overview of digital image processing techniques in MATLAB. It discusses topics such as reading and displaying images, arithmetic operations on images, intensity transformations, spatial filtering, image restoration, working with different image types, morphological operations, and segmentation. Code examples are provided for common image processing functions such as imread(), imshow(), imadd(), imfilter(), rgb2gray(), edge detection filters and thresholding methods.

1. DIGITAL IMAGE PROCESSING
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Dr.S.SHAJUN NISHA, MCA.,M.Phil.,M.Tech.,MBA.,Ph.D
Assistant Professor & Head
PG and Research Dept. of Computer Science
Sadakathullah Appa College
shajunnisha78@gmail.com
+91 99420 96220

2. MATLAB Environment
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3. Procedure to create a new script
NewScript
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4. Saving a new script
SaveSave As
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5. Running a program
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6. IMAGE I/O OPERATIONS
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7. Reading and displaying an Image
Syntax
A = imread(filename)
imshow(A)
Example
rgb=imread(‘peppers.png’)
imshow(rgb)
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8. Displaying output with caption
Syntax
A = imread(filename)
imshow(A)
title(‘caption of the output image')
Example
rgb=imread(‘cameraman.tif’)
imshow(rgb)
title(‘cameraman')
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9. Displaying pair of images
Syntax
imshowpair(I,J,'montage’)
Example
I = imread('cameraman.tif’);
J = imread(‘peppers.png’)
imshowpair(I,J,'montage')
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10. Displaying multiple images using subplot
Syntax
subplot(x,y,z)
Example
I = imread('cameraman.tif');
figure,subplot(3,3,1),imshow(I),title('Cameraman');
J = imread('peppers.png');
subplot(3,3,2),imshow(J),title('Peppers');
k = imread('eight.tif');
subplot(3,3,3),imshow(k),title('eight');
L = imread('rice.png');
subplot(3,3,4),imshow(L),title('rice');
M = imread('onion.png');
subplot(3,3,5),imshow(M),title('onion');
N = imread('pears.png');
subplot(3,3,6),imshow(N),title('pears');
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11. Reading and saving a file
Syntax
f=imread(filename)
imshow(f)
imwrite(f,’filename’)
Example
rgb=imread(‘peppers.png’)
imshow(rgb)
imwrite(rgb,’newrgbfile.jpg’)
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12. Arithmetic operations on image
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13. Adding two images
Syntax
Z = imadd(X,Y)
Example
I = imread('rice.png’);
J = imread('cameraman.tif’);
K = imadd(I,J,'uint16’);
imshow(K,[])
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14. Subtracting images
Syntax
Z = imsubtract(X,Y)
Example
I = imread('rice.png');
J=imread('cameraman.tif');
K = imsubtract(I,J);
imshow(K)
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15. Multiply an image
Syntax
Z = immultiply(X,Y)
Example
a=imread('cameraman.tif’)
imshow(a);
J = immultiply(a,0.5);
figure,imshow(J);
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16. Dividing an image
Syntax
Z = imdivide(X,Y)
Example
I = imread('rice.png');
J = imdivide(I,2);
imshow(J)
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17. Complementing images
Syntax
J = imcomplement(I);
Example
I = imread('cameraman.tif');
J = imcomplement(I);
imshow(J)
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18. Absolute difference of image
Syntax
K = imabsdiff(I,J);
Example
I = imread('cameraman.tif');
J=imread('rice.png');
K = imabsdiff(I,J);
imshow(K)
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19. Mathematical operations
I = imread('rice.png’);
J = imread('cameraman.tif’);
K = imadd(I,J,'uint16’);
figure,subplot(3,3,1),imshow(K),title(‘Addition’);
L = imsubtract(I,J);
subplot(3,3,2),imshow(L),title('Subtraction’);
M = immultiply(J,0.5);
subplot(3,3,3),imshow(M),title('Multiplication');
O = imdivide(J,2);
subplot(3,3,4),imshow(O),title('Division');
P= imcomplement(J);
subplot(3,3,5),imshow(P),title('Complement');
Q = imabsdiff(I,J);
subplot(3,3,6),imshow(Q),title('Absolute difference');
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20. Intensity transformations
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21. Adjusting intensity of an image
Syntax
I=imadjust(filename)
Example
I = imread('cameraman.tif');
J=imadjust(I,[0.5 0.75],[0,1]);
imshowpair(I,J,'montage');
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22. Histogram equalization of an image
Syntax
J=histeq(I)
Example
I = imread('cameraman.tif’);
J=histeq(I,50)
imshowpair(I,J,'montage');
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23. Adaptive histogram equalization
Syntax
J = adapthisteq(I)
Example
I = imread('cameraman.tif’);
J = adapthisteq(I);
imshowpair(I,J,'montage');
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24. Histogram of an image
Syntax
J=histeq(I)
Example
I = imread('cameraman.tif’);
figure,imshow(I);
figure,imhist(I);
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25. Spatial filtering
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26. Applying filter
Syntax
B = imfilter(A,h)
Example
originalRGB = imread('peppers.png’);
imshow(originalRGB)
h = fspecial('motion', 50, 45);
filteredRGB = imfilter(originalRGB, h);
figure, imshow(filteredRGB)
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27. Columnwise neighborhood operations
Syntax
B = colfilt(A,[m n],block_type,fun)
Example
I= imread('tire.tif');
I2 = uint8(colfilt(I,[5 5],'sliding',@mean));
imshow(I) title('Original Image’)
figure imshow(I2)
title('Filtered Image')
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28. Pre defined 2D filter
Syntax
h = fspecial(type)
Example
I= imread('cameraman.tif’);
imshow(I);
H = fspecial('disk',10);
blurred = imfilter(I,H,'replicate’);
imshow(blurred);
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29. 2-D order-statistic filtering
Syntax
B = ordfilt2(A,order,domain)
Example
A = imread('snowflakes.png’);
figure imshow(A)
B = ordfilt2(A,25,true(5));
figure imshow(B)
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30. 2-D median filtering
Syntax
J = medfilt2(I)
Example
I = imread('eight.tif’);
figure, imshow(I)
J = imnoise(I,'salt & pepper',0.02);
K = medfilt2(J);
imshowpair(J,K,'montage')
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31. Image restoration
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32. Add noise to image
Syntax
J = imnoise(I,'gaussian’)
Example
I= imread('eight.tif');
imshow(I)
J = imnoise(I,'salt & pepper',0.02);
imshow(J)
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33. Deblur image using regularized filter
Syntax
J = deconvreg(I,psf)
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34. Deblur image using Wiener filter
Syntax
J = deconvwnr(I,psf,nsr)
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35. Taper discontinuities along image edges
Syntax
J = edgetaper(I,PSF)
Example
original = imread('cameraman.tif’);
PSF = fspecial('gaussian',60,10);
edgesTapered = edgetaper(original,PSF);
figure, imshow(original,[]);
figure, imshow(edgesTapered,[]);
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36. Working with different types of
images
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37. Color image to gray scale image
Syntax
I = rgb2gray(RGB)
Example
RGB = imread('peppers.png’);
imshow(RGB)
I = rgb2gray(RGB);
figure imshow(I)
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38. Convert grayscale or binary image to indexed
image
Syntax
[X,cmap] = gray2ind(I,c)
Example
I = imread('cameraman.tif');
[X, map] = gray2ind(I, 16);
imshow(X, map);
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39. Convert indexed image to grayscale image
Syntax
I = ind2gray(X,cmap)
Example
[X, map] = imread('trees.tif');
I = ind2gray(X,map);
imshow(X,map) ;
title('Indexed Image’)
figure imshow(I);
title('Converted Grayscale Image')
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40. Convert RGB image to indexed image
Syntax
[X,cmap] = rgb2ind(RGB,Q)
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41. Convert grayscale image to indexed image
using multilevel thresholding
Syntax
X = grayslice(I,N)
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42. Morphological operations
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43. Dilate image
Syntax
J = imdilate(I,SE)
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44. Erode image
Syntax
J = imerode(I,SE)
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45. Morphologically open image
Syntax
J = imopen(I,SE)
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46. Morphologically close image
Syntax
J = imclose(I,SE)
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47. Morphological operations on binary images
Syntax
BW2 = bwmorph(BW,operation)
remove skeleton
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48. Morpological reconstruction
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49. Fill image regions and holes
Syntax
BW2 = imfill(BW,locations)
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50. Morphological reconstruction
Syntax
J = imreconstruct(marker,mask)
original image eroded image
reconstructed image
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51. Segmentation
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52. Find edges in intensity image
Syntax
BW = edge(I)
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53. Canny operator
Syntax
BW = edge(I,’canny’)
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54. Prewitt Operator
Syntax
BW = edge(I,’prewitt’)
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55. Roberts operator
Syntax
BW = edge(I,’roberts’)
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56. Sobel operator
Syntax
BW = edge(I,’sobel’)
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57. Laplacian of Gaussian(LoG)
Syntax
BW = edge(I,’log’)
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58. Global Thresholding
Syntax
g=im2bw(I,T); T=0.2 T=0.5
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59. Global image threshold using Otsu's method
Syntax
T = graythresh(I)
Example
I = imread('coins.png');
level = graythresh(I)
BW = imbinarize(I,level);
imshowpair(I,BW,'montage')
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