"Index exceeds matrix dimensions" error during performing RGB channel separation

1 view (last 30 days)
The purpose of my code is -
  1. scan all image from a folder
  2. calculate entropy for each of RGB channel
  3. export data to a xlsx file
my code :
folder = 'F:\images\';
filePattern = fullfile(folder, '*.png');
myFiles = dir(filePattern); % the folder inwhich ur images exists
for k = 1 : length(myFiles)
fullFileName = fullfile(folder, myFiles(k).name);
I= fullFileName;
Red = I(:,:,1);
Green = I(:,:,2);
Blue = I(:,:,3);
%I = I(:); % Vectorization of RGB values
p = imhist(Red); % Histogram
p(p == 0) = [ ];% remove zero entries in p
p = p ./ numel(I); % normalize p so that sum(p) is one.
Er(k) = round(-sum(p.*log2(p)),3);
p = imhist(Blue); % Histogram
p(p == 0) = [ ];% remove zero entries in p
p = p ./ numel(I); % normalize p so that sum(p) is one.
Eb(k) = round(-sum(p.*log2(p)),3);
xlswrite('myfile.xlsx', [Er(k),Eb(k)], 'Sheet 1');
end
But i am getting following error:
Index exceeds matrix dimensions.
Error in test1 (line 9)
Green = I(:,:,2);
I couldn't solve this problem. Can anyone help me please?

Accepted Answer

Simon Chan
Simon Chan on 25 Jul 2021
According to your code shown above, variable I is only a file name in the beginning of the for loop.
Have you do imread or some other command to read the images?
for k = 1 : length(myFiles)
fullFileName = fullfile(folder, myFiles(k).name);
I= imread(fullFileName); % I added imread
Red = I(:,:,1);
Green = I(:,:,2);
Blue = I(:,:,3);
  4 Comments
Simon Chan
Simon Chan on 25 Jul 2021
Doing transpose:
xlswrite('myfile.xlsx', [Er',Eb'], 'Sheet 1');
or
writematrix([Er',Eb'],'myfile.xlsx');

Sign in to comment.

More Answers (1)

Yongjian Feng
Yongjian Feng on 24 Jul 2021
Most likely your image is just a grey scale one. Only one channel.
  1 Comment
rakib mostafiz
rakib mostafiz on 24 Jul 2021
Those image are colorful. Moreover, if i perform this operation on a single image rather than looping out all image from folder, it works just fine! But when i try to read each image and perform this operation, it showing that error. I really dont understand the problem here

Sign in to comment.

Categories

Find more on Large Files and Big Data in Help Center and File Exchange

Products


Release

R2015b

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!