I AM GETTING INDEX EXCEEDS MATRIX DIMENSIONS error? PLEASE HELP?

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Aniket Paranjpe 2017-11-13

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评论： Aniket Paranjpe 2017-11-29

The following code is used for digital image watermarking using the feature points of the cover image I am getting the following error: Index exceeds matrix dimensions. Error in Algo1 (line 115) M(i1,j1)=a1(i1,j1); Please tell me how to resolve this error code (m file attached for reference)

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Walter Roberson 2017-11-15

Unfortunately we do not have lena.bmp or watermark.png to test with.

Aniket Paranjpe 2017-11-18

I Have attached the test images now too.

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Answer 1

Walter Roberson 2017-11-18

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在 MATLAB Online 中打开

Near line 120, you have

i=1:floor(l/l1);

At that point, l is 64 and l1 is 512, so floor(l/l1) is 0 and i = 1:0 which is empty. Then a small number of lines further down,

for i1=1:l1
    for j1=1:m1
        temp=i1+(i-1)*l1;
        temp1=j1+(j-1)*m1;
        M(i1,j1)=a1(temp,temp1);
    end
end

with i being empty, temp becomes empty, and a1 gets indexed with the empty vector, giving an empty result. The empty result cannot be stored in the non-empty M(i1,j1)

Now suppose that you had

i=1:floor(l1/l);

giving i=1:512/64 which is i=1:8 . Then with i being a vector, temp=i1+(i-1)*l1 would be a vector, and a1(temp,temp1) would be addressing multiple locations. You cannot store multiple locations in the single location M(i1,j1) either. Therefore that loop is probably wrong.

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Walter Roberson 2017-11-27

Algo1.m

You must have made a typing mistake in the conversion.

Your code was also missing an opening quote mark for an imwrite, and it used the undefined function imscale(). If imscale was intended to be https://www.mathworks.com/matlabcentral/fileexchange/21251-geoml?focused=5104132&tab=function then it was being called incorrectly.

I have attached code that runs.

Aniket Paranjpe 2017-11-29

@ walter roberson this piece of code works,thankyou

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Answer 2

Jan 2017-11-13

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在 MATLAB Online 中打开

Start with an auto-indentation to make the code readable: Ctrl-A Ctrl-I. Omit the brute clearing header "clc; close all; clear all;" - there is no reason to clear e.g. all loaded function from the RAM and waste time with reloading from the slow disk.

I cannot run your code due to missing input data and toolboxes.

The code looks strange:

for i1=1:l1
  for j1=1:m1
    temp=i1+(i-1)*l1;
    temp1=j1+(j-1)*m1;
    M(i1,j1)=a1(i1,j1);
  end
end

What is the reason for overwriting temp and temp1 in each iteration? This would be much simpler:

M = a(1:l1, 1:m1);

But you should get the same error: Obviously a has either less than l1 rows or less than m1 columns. You can find out the details using the debugger:

dbstop if error

Then run the code again. When it stops, check the current values of i1 and j1 as well as the dimension of a1.

The missing comments impede the clarity of the code massively. I would not dare to debug this code or use it.

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Aniket Paranjpe 2017-11-14

I Have added a few comments about what the code does, also i have indented the code properly. please go through updated m-file and help me resolve this error

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