bugGNU Octave - Bugs: bug #56169, [octave forge] (image) images of...

 
 

bug #56169: [octave forge] (image) images of class double or single fail to convert to class uint8

Submitted by:  None
Submitted on:  Fri 19 Apr 2019 08:02:06 AM UTC  
 
Category:  Octave Forge Package Severity:  3 - Normal
Priority:  5 - Normal Item Group:  None
Status:  None Assigned to:  None
Originator Name:  Originator Email:  -email is unavailable-
Open/Closed:  Open Release:  5.1.0
Operating System:  Microsoft Windows

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Sat 20 Apr 2019 01:53:11 AM UTC, comment #1:

Where was the `im` data sourced from? It's hard to reproduce this without a full example. Can you attach an example input file to this issue?

Maybe you're not supposed to call im2uint8 on LAB-space image data? I don't know that the data structures used by the image toolbox have enough metadata for the functions to know whether they're RGB or LAB-space images. So maybe it's seeing that the input is a double, assuming it's RGB, in which case the values should have been in the interval [0.0 1.0], so these LAB values which are >1 are just saturating it and pegging all the values to 1.0, which gets normalized to 255 in uint8 space.

Andrew Janke <apjanke>
Fri 19 Apr 2019 08:02:06 AM UTC, original submission:

>> lab = rgb2lab(im);
>> im(1:10,1:10,1)

ans =

21 21 21 21 22 23 22 18 20 23
24 23 21 21 21 20 20 19 21 22
23 23 22 21 21 20 20 20 21 20
25 23 21 21 21 22 22 22 23 24
21 21 21 21 21 22 20 22 23 24
25 22 21 21 21 21 21 21 22 23
23 21 21 22 22 22 23 20 20 23
25 24 24 22 22 22 23 23 24 24
24 24 22 22 21 21 22 20 22 24
26 23 21 21 22 22 20 19 20 23

>> lab(1:10,1:10,1)

ans =

34.908 32.971 32.649 31.366 32.296 32.911 31.653 30.946 31.108 31.565
34.340 32.965 32.762 31.892 31.570 31.603 31.925 31.697 31.745 31.451
34.525 33.343 32.674 32.483 31.513 32.514 32.784 32.784 32.428 31.811
34.362 33.343 32.064 32.271 31.513 32.296 31.749 31.749 33.128 32.725
34.157 33.941 32.647 32.807 31.835 31.216 32.191 31.216 32.210 33.102
34.629 33.428 31.686 31.628 32.103 31.399 31.686 30.410 31.711 32.965
34.954 33.460 29.527 31.314 31.595 31.274 31.016 31.208 31.589 32.533
36.233 33.960 33.314 32.399 31.805 32.019 32.478 31.887 32.614 33.102
36.209 34.604 33.051 31.694 32.374 31.456 31.481 31.165 31.102 31.271
35.565 35.274 33.140 32.807 31.917 30.694 32.135 31.511 32.079 32.424

>> a = im2uint8(lab);
>> size(a)

ans =

308 168 3

>> class(a)

ans = uint8

>> a(1:10,1:10,1)

ans =

255 255 255 255 255 255 255 255 255 255
255 255 255 255 255 255 255 255 255 255
255 255 255 255 255 255 255 255 255 255
255 255 255 255 255 255 255 255 255 255
255 255 255 255 255 255 255 255 255 255
255 255 255 255 255 255 255 255 255 255
255 255 255 255 255 255 255 255 255 255
255 255 255 255 255 255 255 255 255 255
255 255 255 255 255 255 255 255 255 255
255 255 255 255 255 255 255 255 255 255

>>

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Anonymous

 

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    Follow 2 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2019-04-19 mtmiller CategoryOctave Function => Octave Forge Package
        Summaryimages of class double or single fail to convert to class uint8 => [octave forge] (image) images of class double or single fail to convert to class uint8

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