Image Rotation in MATLAB - Examples without imrotate function – Part 2

To flip an image left to right without using ‘fliplr’

Grayscale:

 A = imread('cameraman.tif');

 LR = A(1:end,end:-1:1);

 figure, subplot(1,2,1);imshow(A);title('original');         

         subplot(1,2,2);imshow(LR);title('Flipped left to right');

RGB Image:

RGB = imread('peppers.png');

 LR  = RGB(1:end,end:-1:1,:);

 figure, subplot(1,2,1);imshow(RGB);title('original');         

         subplot(1,2,2);imshow(LR);title('Flipped left to right');

To flip an image upside down without using ‘flipud’

Gray Scale:

 A = imread('liftingbody.png');

 UD = A(end:-1:1,1:end);

 figure, subplot(1,2,1);imshow(A);title('original');         

         subplot(1,2,2);imshow(UD);title('Upside Down');

RGB Image:

 UD = RGB(end:-1:1,1:end,:);

 figure, subplot(1,2,1);imshow(RGB);title('original');         

         subplot(1,2,2);imshow(UD);title('Upside Down');

MATLAB code to rotate a gray scale Image:

A = imread('cameraman.tif');

%Specify the degree

deg = 35;

%Find the midpoint

if(deg > 155)

    midx = ceil((size(A,1))/2);

    midy = ceil((size(A,2))/2);

else

    midx = ceil((size(A,2))/2);

    midy = ceil((size(A,1))/2);

end

[y,x] = meshgrid(1:size(A,2), 1:size(A,1));

[t,r] = cart2pol(x-midx,y-midy);

t1 = radtodeg(t)+deg;

%Convert from degree to radians

t = degtorad(t1);

%Convert to Cartesian Co-ordinates

[x,y] = pol2cart(t,r);

%Add the mid points to the new co-ordinates

tempx = round(x+midx);

tempy = round(y+midy);

if ( min(tempx(:)) < 0 )

   

newx = max(tempx(:))+abs(min(tempx(:)))+1;

tempx = tempx+abs(min(tempx(:)))+1;

else

    newx = max(tempx(:));

end

if( min(tempy( : )) < 0 )

   

newy = max(tempy(:))+abs(min(tempy(:)))+1;

tempy = tempy+abs(min(tempy(:)))+1;

else

    newy = max(tempy(:));

end

tempy(tempy==0) = 1;

tempx(tempx==0) = 1;

C = uint8(zeros([newx newy]));

for i = 1:size(A,1)

    for j = 1:size(A,2)

        C(tempx(i,j),tempy(i,j)) = A(i,j);

       

    end

  

end

figure,imshow(C);

Output = C;

%FILL THE HOLES OR GAPS-NEAREST NEIGHBOR

for i = 2:size(C,1)-1

    for j = 2:size(C,2)-1

       

        temp = C(i-1:i+1,j-1:j+1);

        if(temp(5)==0&&sum(temp(:))~=0)

            pt = find(temp~=0);

           

            [~,pos] = sort(abs(pt-5));

            Output(i,j) = temp(pt(pos(1)));

          

        end

       

    end

end

figure,imshow(uint8(Output));

EXPLANATION:

This is a faster implementation of the older versionand also the gaps are filled with the nearest neighbor .

MATLAB code to rotate a RGB Image

A=imread('peppers.png');

%Specify the degree

deg=45;

%Find the midpoint

if(deg>155)

    midx = ceil((size(A,1))/2);

    midy = ceil((size(A,2))/2);

else

    midx = ceil((size(A,2))/2);

    midy = ceil((size(A,1))/2);

end

[y,x] = meshgrid(1:size(A,2), 1:size(A,1));

[t,r] = cart2pol(x-midx,y-midy);

t1 = radtodeg(t)+deg;

%Convert from degree to radians

t = degtorad(t1);

%Convert to Cartesian Co-ordinates

[x,y] = pol2cart(t,r);

tempx = round(x+midx);

tempy = round(y+midy);

if ( min(tempx ( : ) ) < 0 )

   

newx = max(tempx(:))+abs(min(tempx(:)))+1;

tempx = tempx+abs(min(tempx(:)))+1;

else

    newx = max(tempx(:));

end

if( min(tempy ( : ) ) < 0 )

   

newy = max(tempy(:)) + abs(min(tempy(:)))+1;

tempy = tempy + abs(min(tempy(:)))+1;

else

    newy = max(tempy(:));

end

tempy(tempy==0) = 1;

tempx(tempx==0) = 1;

C = uint8(zeros([newx newy 3]));

for i = 1:size(A,1)

    for j = 1:size(A,2)

        

        C( tempx(i,j),tempy(i,j) ,:) = A(i,j,:);

      

       

    end

  

end

figure,imshow(C);

Output=C;

%FILL THE HOLES OR GAPS - NEAREST NEIGHBOR

for i = 2:size(C,1)-1

    for j = 2:size(C,2)-1

       

        temp = C(i-1:i+1,j-1:j+1,:);

        if(temp(5)==0 && sum(temp(:))~=0)

           

             pt = find(temp(:,:,1)~=0);

            [~,pos] = sort(abs(pt-5));

           

            temp = C(i-1:i+1,j-1:j+1,1);

            Output(i,j,1) = temp(pt(pos(1)));

           

            temp = C(i-1:i+1,j-1:j+1,2);

            Output(i,j,2) = temp(pt(pos(1)));

           

            temp = C(i-1:i+1,j-1:j+1,3);

            Output(i,j,3) = temp(pt(pos(1)));

        end

       

    end

end

figure,imshow(uint8(Output));title([num2str(deg),'Degree']);