# Rotating an image counterclockwise

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Oah Joan on 20 Nov 2018
Edited: John Kelly on 15 Jan 2021
I want to write a function myimrotateimage(image,angle) that rotates a greyscale OR color image counterclockwise by the angle specified in degrees. The function below only seems to work for greyscale images, everytime I use a color image I get an error and i am unsure why. Can anyone explain why and how I can fix it? (WITHOUT USING imrotate)
function imagerot = imrotategrey(image,angle)
[Rows, Cols] = size(image);
Diagonal = sqrt(Rows^2 + Cols^2);
Row2 = ceil(Diagonal - Rows) + 2;
Col2 = ceil(Diagonal - Cols) + 2;
image2 = zeros(Rows+Row2, Cols+Col2);
image2(ceil(Row2/2):(ceil(Row2/2)+Rows-1),ceil(Col2/2):(ceil(Col2/2)+Cols-1)) = image;
%midpoints
midx=ceil((size(image2,1)+1)/2);
midy=ceil((size(image2,2)+1)/2);
imagerot=zeros(size(image2)); % midx and midy same for both
for i=1:size(imagerot,1)
for j=1:size(imagerot,2)
x= (i-midx)*cosd(angle)+(j-midy)*sind(angle);
y=-(i-midx)*sind(angle)+(j-midy)*cosd(angle);
x=round(x)+midx;
y=round(y)+midy;
if (x>=1 && y>=1 && x<=size(image2,2) && y<=size(image2,1))
imagerot(i,j)=image2(x,y); % k degrees rotated image
end
end
end
end
Rena Berman on 15 Jan 2021

Image Analyst on 20 Nov 2018
Edited: Image Analyst on 20 Nov 2018
Because you got the size wrong. It should be
[Rows, Cols, numberOfColorChannels] = size(image);
Also, DO NOT use image as the name of your variable since that is already the name of a built-in function. Likewise, don't use any other function either, like size, sum, min, max, etc.