DCT code for image hash

Question

Sundara Krishnan N 2018-2-4

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/380708-dct-code-for-image-hash

回答： Abhishek Ballaney 2018-2-5

I am working on a project to assign fingerprint to images using pHash. I happened to get the following code from StackOverflow:

% read image
I = imread('cameraman.tif');
% cosine transform and reduction
d = dct2(I);
d = d(1:8,1:8);
% compute average
a = mean(mean(d));
% set bits, here unclear whether > or >= shall be used
b = d > a;
% maybe convert to string:
string = num2str(b(:)');

When I run the code, I get the following errors, all of which are associated with built-in functions:

Matrix dimensions must agree.
Error in dct (line 76)
  b = W .* fft(y);
Error in dct2 (line 50)
    b = dct(dct(arg1).').';
Error in flipimage (line 4)
d = dct2(I);