IMWRITE followed by IMREAD Changes Pixel Values

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Ajmal
Ajmal 2013-8-19
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)

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采纳的回答

Amith Kamath
Amith Kamath 2013-8-19
编辑：Amith Kamath 2013-8-19
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.

更多回答（1 个）

Image Analyst
Image Analyst 2013-8-19
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.

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