Image extensions in MATLAB

Graphics Interchange Format

To extract frames from GIF file.

The image is usually an animated GIF file.

The multiframes are read using the syntax: imread(filename, ‘frames’, ‘all’)

To read ‘n’ number of frames from a GIF file: imread(filename, ‘frames’, 1:n)

Example:

Here, the GIF image is an animated file and contains 8 frames.

The frames that are read will be stored in a 4-D format.

 [A,map]=imread('cute.gif','frames','all');

mov=immovie(A,map);

implay(mov);

To animate the muliframes: use  ‘immovie’ to make a movie from the muliframe image.

Play the movie using ‘implay’.

To view a particular frame:

imshow(A(:,:,4),map);  Here the 4th frame is viewed.

To create avi file from the movie:

movie2avi(mov, 'cute_girl.avi', 'compression', 'None','fps',3);

Here frames per second(fps) is 3. 

Image Shading in MATLAB

         
              Here I tried to shade the RGB image which results in a pencil sketched type image. The user selects the image from the pop-up menu and by adjusting the line value in the slider, the edge thickness is made.

By adjusting the thresh value in the slider the image shade is increased or decreased.
Additional Information:
To make your own pencil sketch without using MATLAB try Autodesk Sketchbook.
Based on the customers review, this software is best to try on low pixel camera images.

Steps To Be Performed:

1.     Input a RGB image

2.     Convert the image to grayscale image.

3.     Find the edges using Sobel Method.[gradient Estimation]

4.     Filter the Image to obtain the image without noise

4.1.          The blurred or unsharp image is subtracted from the image to obtain the sharpened image.

5. Blend the edge and the sharpened image.

MATLAB Code:

function image_shade

The GUI is designed.

global filename A;

scz=get(0,'ScreenSize');

figure('Position',[round(scz(1,3)/4) round(scz(1,4)/8) 700 500],'MenuBar','None','NumberTitle','off','Name','Pencil sketch Application','Resize','off');

axes('Position',[0 0 .7 1],'xtick',[],'ytick',[]);

shade=uicontrol('Style','slider','Position',[500,310 200 20],'Max',1 ,'Min',0.01,'Value',0.56,'Callback',@draw);

thresh=uicontrol('Style','slider','Position',[500,370 200 20],'Max',255,'Min',0,'Value',30,'Callback',@draw);

directory=dir('*.jpg');

files={directory.name}';

tval=uicontrol('style','text','Position',[500,340 100 20]','String','Thresh :');

line=uicontrol('style','text','Position',[500,395 100 20]','String','Line :');

uicontrol('style','text','Position',[500,455 100 20]','String','Filename:');

uicontrol('Style','popupmenu','position',[500 420 160 30],'Value',1,'String',files,'Callback',@displayfile);

    function displayfile(obj,~)

        ptr=get(obj,'value');

        filename=char(files(ptr));

        A=imread(filename);                      

        imshow(A);

    end

    function draw(~,~)

       

        sh=get(shade,'Value');

        thr=get(thresh,'Value');

        thval=strcat('Thresh :', num2str(sh));

        set(tval,'String',thval);

       

        lineval=strcat('Line :', num2str(thr));

        set(line,'String',lineval);

       if(~isempty(A))

        A=imread(filename);

        B=rgb2gray(A);

The Edge of the image is detected using the sobel edge detection method.

C3=~edge(B,'sobel','VERTICAL');

C2=~edge(B,'sobel','HORIZONTAL');

C=uint8(C3.*C2);

The image is sharpened by subtracting the blur image.

F1=uint8(imfilter(B,fspecial('unsharp')/sh));

The blending of the edge and the filtered image is done.

for m=1:size(F1,1)

    for n=1:size(F1,2)

        if(C(m,n)==0)

           F1(m,n)=B(m,n)-thr;

        end

    end

end

imshow(F1);

       end

    end

end

Shaded Image

Original Image

Image Arithmetic in MATLAB with example

Image Arithmetic

    An image is represented in a matrix format.

    To perform image arithmetic the size of the two matrices should be same.

    The operation on two images results in a new image.

    Consider two images A and B with same size.

Image Addition

    In a RGB image, the addition of two images can be done using the ‘+’ operator. C=A+B;

Here, the minimum value of A+B and 255 is taken.

(i.e) C(i,j,1)=min(A(i,j,1)+B(i,j,1),255) where (i,j) represents the pixel position.

Image addition can be used to add the components from one image into other image.

Image Subtraction

A new image is obtained as a result of the difference between the pixels in the same location of the two images being subtracted.

C=A-B; ie. Maximum value of A-B and zero.

C(i,j,:) =max(A(i,j,:)-B(i,j,:),0).

Image subtraction is widely used for change detection.

For detecting the missing components in product assembly,

Example:To detect the defects in the PCB.

Image subtraction is most beneficial in the area of medical image processing called mask mode radiography.

   

Image Multiplication

Image multiplication is used to increase the average gray level of the image by multiplying with a constant.

It is used for masking operations.

C=A.*B;

Image Division

Image division can be considered as multiplication of one image and the reciprocal of other image.

C=A.\B;

Logical Operations:

Logical operations are done on pixel by pixel basis.

The AND and OR operations are used for selecting subimages in an image .

This masking operation is referred as Region Of Interest processing.

Logical AND

To isolate the interested region from rest of the image portion logical AND or OR is used. Consider a mask image L for the image A.

To obtain the interested area, D= and(L,A) ;

We can use L&A also.

The resulting image will be stored in D which contains the isolated image part.

Logical OR

Syntax: D=or(L,A). We can also use L|A

background=imread('back.jpg');

A=imread('tommy1.bmp');

B=imread('jerry1.bmp');

%Image addition

%Both A and B are of same size

object=A+B;

background=imresize(background,[size(object,1) size(object,2)]);

Im3=uint8(zeros(size(object)));

whiteImg=uint8(ones(size(object)));

%Array right division. A./B is the matrix with elements A(i,j)/B(i,j). A and B must

%have the same size, unless one of them is a scalar.

%Image Division

mask=whiteImg./object;
%Logical AND

im3=uint8(mask&background);%uint8(and(mask,background));

figure,imshow(mask);

%Array multiplication. A.*B is the element-by-element product of the arrays A and B.

%Image multiplication

%Multiply the background and the mask image

%And the result with the foreground image to obtain the final Image.

finalImg=(background.*im3)+object;

figure,imshow(finalImg);

MATLAB Programming for Engineers

Example:2

img61.jpg

Sample_Image.jpg

D=imread('img61.jpg');

E=imread('Sample_Image.jpg');

 D=imresize(D,[size(E,1) size(E,2)]);

 A=double(E);

 C=uint8(zeros(size(A)));

 F=E;

 [x,y]=find((A(:,:,1)+A(:,:,2)+A(:,:,3))>650);

 for i=1:size(x,1)

    C(x(i),y(i),:)=1; 

    F(x(i),y(i),:)=0;    

 end

 C=C.*D;

  

  C=C+F;

  imshow(C);