Array divided by 255 gives me 0

I have an matrix that looks like this (but bigger)

[30 29 31; 
 29 30 30;
 30 31 30]

now when I divide it by 255, it gives me this:

[0 0 0; 
 0 0 0;
 0 0 0]

As far as I know I never changed anything with digits, does anyone have an idea what's going on?

Kind regards

edit: the matrix contains doubles

Answer 1

[Joep]

This is because you matrix was written in uint8. You should first convert it to double.

double([30 29 31; 29 30 30; 30 31 30])

It's not clear why it is in uint8 maybe you load some image or create uint8 matrix.

PS: uint8 means you got a 8 bit number so 2^8=256 which will give 0->255. If you need some help I can help you also in dutch.

[Thomas Koelen]

I already converted it to double, I just didn't show it on the post. It didn't work, then I reopened Matlab and it did work. I don't know what was wrong, guess I'll never know :P

[James Tursa]

Most likely you thought you had converted it to double, but hadn't. Then you restarted MATLAB and wiped out the evidence.

Answer 2

[Ilham Hardy]

testmat = [30 29 31; 29 30 30; 30 31 30] ;

testmat =

    30    29    31
    29    30    30
    30    31    30

>> testmatdev = testmat./255

testmatdev =

    0.1176    0.1137    0.1216
    0.1137    0.1176    0.1176
    0.1176    0.1216    0.1176

[Thomas Koelen]

It's not working either, ran my code on another pc and it's working just fine. After reopening Matlab on my own computer it's also running fine.

Thanks though!