MATLAB Answers

Ajmal
0

IMWRITE followed by IMREAD Changes Pixel Values

Asked by Ajmal
on 19 Aug 2013
I have an image matrix
aa 150x200x3 720000 double
With pixel values 0-255
Why does this test fail :
imwrite(aa, 'aatest.png');
aanew = imread('aatest.png');
isequal(aa, aanew)

  0 Comments

Sign in to comment.

2 Answers

Answer by Amith Kamath on 19 Aug 2013
Edited by Amith Kamath on 19 Aug 2013
 Accepted Answer

I tried this, and I realized that ISEQUAL compares a DOUBLE and UINT8, which quite obviously does not return true.
p = rand(150,200,3);
imwrite(p,'test.png');
pnew = imread('test.png');
isequal(p,pnew)
if you really want to check equality,
isequal(im2uint8(p),pnew)
is the way to go.

  0 Comments

Sign in to comment.


Answer by Image Analyst
on 19 Aug 2013

I don't believe PNG is meant for doubles, though I could be wrong. Anyway I never try to save color images while in a double class unless it's to a mat file. Try casting your aa array to uint8 before you save it out. I think that's really what you want and intended anyway.

  0 Comments

Sign in to comment.