Add salt and pepper noise to image

How to add salt and pepper noise to an image

          To obtain an image with ‘speckle’ or ‘salt and pepper’ noise we need to add white and black pixels randomly in the image matrix.

First convert the RGB image into grayscale image.

Then generate random values for the size of the matrix.

Here I used MATLAB function ‘randint’.

This function will generate random values for the given matrix size within the specified range.

For instance, consider an image matrix of size 4X3

Imgmatrix =

   237   107   166

   234    95   162

   239   116   169

   56   126    89

Generate random values for a 4X3 matrix with range 0 to 10.

randint(4,3,[0,10])

ans =

     4    10     4

     7     8     4

    10     0     5

     3    10     9

    

Now we can replace with pixel value zero (black) in the image matrix if there is ‘0’ value in the random matrix.

Now the image matrix will have black pixels.

Imgmatrix =

   237   107   166

   234    95   162

   239   0   169

   56   126    89

 

Similarly, replace the image matrix pixel value with ‘255’ if there is value ‘10’ in the random matrix.

The white pixels are now added.

Imgmatrix =

   237   255   166

   234    95   162

   255   0   169

   56   126    89

Black=0 white=255

 

MATLAB CODE:

A=imread('taj.jpg');

B=rgb2gray(A);

black=3;

white=253;

%Adjust the values in 'black' and 'white' to increase the noise.

NoiseImg = B;

    Rmatrix = randint(size(B,1),size(B,2),[0,255]);

    NoiseImg(Rmatrix <= black) = 0;

    NoiseImg(Rmatrix >=white) = 255;

    RImg=medfilt2(NoiseImg);

    figure,subplot(1,2,1),imshow(NoiseImg),title('Add ''Salt and Pepper'' Noise');

    subplot(1,2,2),imshow(RImg),title('After Noise Removal');

 I used the MATLAB function 'medfilt2' to remove noise. 

Learn how to remove the noise without using the 'medfilt2' function.

I can't sleep Illusion

In this illusion, I used slanted lines in two different directions  to highlight the foreground from the background.

First, the background is formed with slanting lines in one direction.

Steps to form background with slanting lines:

1.       Get the size of the foreground image. For instance, MXN =5X8

2.       Initialize a matrix of size 1XN=1X8.

3.       Generate values for the matrix.
Eg. [10  10 250 250 10 10 250 250]ie [BBWWBBWW] B-Black, W-White

4.       Initialize another matrix of size MXN. In the first row copy the random values.

5.       For the second row perform circshift. By circshift the pixel at the first column will be moved to the last column and the remaining pixels are shifted to left by one.Eg [10 250 250 10 10 250 250 10].
      Now the colors will be [BWWBBWWB].

6.       Continue to perform circshift  for all the rows.  Now the slanting lines are formed.
   10    10   250   250    10    10   250   250

   10   250   250    10    10   250   250    10

   250   250    10    10   250   250    10    10

   250    10    10   250   250    10    10   250

    10    10   250   250    10    10   250   250

MATLAB CODE:

%Read the Image

TImg=imread('sleep.jpg');

m=size(TImg,1);

n=size(TImg,2);

if(mod(n,2)~=0)

    n=n-mod(n,2);

end   

if(mod(n,4)~=0)

        n=n-mod(n,4);

end

BImg=uint8(zeros([1 n 3]));

flag=0;

%Values for first column (bbwwbbwwbbww)

for i=1:2:n

    if(flag==1)

            BImg(1,i:i+1,:)=10;

            flag=0;

    else

            BImg(1,i:i+1,:)=240;

            flag=1;

    end

end

%Initialization

A=uint8(zeros([m size(BImg,2) 3]));

Arot=uint8(zeros([m size(BImg,2) 3]));

SImg=uint8(zeros([m size(BImg,2) 3]));

FImg=uint8(zeros([m size(BImg,2) 3]));

A(1,:,:)=BImg(1,:,:);

%Slanting lines

for i=2:m

    BImg=circshift(BImg,[1,-1]);

    A(i,:,:)=BImg(1,:,:);

end

Steps to perform on foreground Image:

1.       Rotate the background image from left to right.

2.       Convert the foreground image into binary image and negate it. Then perform image multiplication with the rotated background image.

MATLAB CODE:

%Flip the image from left to right

Arot(:,:,1)=fliplr(A(:,:,1));

Arot(:,:,2)=fliplr(A(:,:,2));

Arot(:,:,3)=fliplr(A(:,:,3));

%Foreground

BImg=uint8(~im2bw(TImg));

BImg=imresize(BImg,[size(Arot,1) size(Arot,2)]);

SImg(:,:,1)=BImg.*Arot(:,:,1);

SImg(:,:,2)=BImg.*Arot(:,:,2);

SImg(:,:,3)=BImg.*Arot(:,:,3);

SImg(SImg==0)=1;

Image Mask:

1.       Multiply the background image with the binary foreground image to obtain the mask.

MATLAB CODE:

%Background Image mask

BImg1=uint8(im2bw(TImg));

BImg1=imresize(BImg1,[size(Arot,1) size(Arot,2)]);

FImg(:,:,1)=BImg1.*A(:,:,1);

FImg(:,:,2)=BImg1.*A(:,:,2);

FImg(:,:,3)=BImg1.*A(:,:,3);

FImg(FImg==0)=1;

Combine Foreground Image and the background Image mask.

MATLAB CODE:

%Combine Background mask with foreground.

Zig=FImg.*SImg;

figure,imshow(Zig);

            

GUESS THE IMAGE: 
If you can read this then give your reactions...

I used square font to make this illusion. You can download the font at:http://fontzone.net/font-download/SF+Square+Head+Bold/

Check this link for more optical Illusion Images: Images from Blog

Black and White-Optical illusion

Today, Some of my friends in Facebook posted black and white optical illusion photo saying 'ITS FREAKING AWESOME'.
After seeing the image, I found it's actually black and white illusion. Yes, convert the image to binary and do logical not of the image. When you look or concentrate at one point on the image ,maybe in center you can see a logical not of the image (i.e) White pixels will be black and black pixels will be white.

The most interesting thing is, you can try with your own photo.

MATLAB CODE:


A=imread('illusion.jpg');

B=uint8(zeros(size(A)));
A=~im2bw(A);

Logical Not on Binary Image

for i=1:size(A,1)
    for j=1:size(A,2)
        if(A(i,j)==1)
            B(i,j,:)=255;
        end
    end
end

Stare at the dots on image for 20 to 30 secs. Close your eyes or look up towards the ceiling.
You can see a binary image. i.e im2bw(A);

To draw the dots on the image:

C=uint8(ones(4 ,4, 3));
C(:,:,1)=C(:,:,1)*200;
C(:,:,2)=C(:,:,2)*0;
C(:,:,3)=C(:,:,3)*250;
%Find the mid point of the image and draw 3 dots.


midx=round(size(B,1)/2);
midy=round(size(B,2)/2)+30;
for i=1:size(C,1)
    for j=1:size(C,2)
B(midx+i+5,midy+j,:)=C(i,j,:);
B(midx+i-5,midy+j,:)=C(i,j,:);
B(midx+i+15,midy+j,:)=C(i,j,:);
    end
end

Check this Illusion also:I cant sleep Illusion
Check this link for more optical Illusion Images: Images from Blog