MATLAB Answers

YT
1

Imwrite JPG with comments

Asked by YT
on 6 Feb 2019
Latest activity Commented on by Walter Roberson
on 12 Feb 2019
I'm trying to save my images with some comments like so
imwrite(imageData, '/MATLAB Drive/ArtScraper/out_img/Ukiyo-e_1549412662/592fa615edc2c933948514b7.jpg' 'Comment', {['Title: ' nStyle(jj).title '; Author: ' nStyle(jj).artistName '; Year: ' nStyle(jj).year]});
To check if the comments were written correctly I used imfinfo
struct with fields:
Filename: '/MATLAB Drive/ArtScraper/out_img/Ukiyo-e_1549412662/592fa615edc2c933948514b7.jpg'
FileModDate: '06-Feb-2019 00:36:24'
FileSize: 37242
Format: 'jpg'
FormatVersion: ''
Width: 327
Height: 520
BitDepth: 24
ColorType: 'truecolor'
FormatSignature: ''
NumberOfSamples: 3
CodingMethod: 'Huffman'
CodingProcess: 'Sequential'
Comment: {'Title: Ichikawa Monnosuke Ii as Date No Yosaku in the Kabuki Play "koi-nyōbō Somewake Tazuna"; Author: Tōshūsai Sharaku; Year: 1794'}
Now I was under the assumption that image now contains comments if I'd check the properties but sadly that wasn't the case
So I'm either doing something wrong with writing comments to my images or the comments are only visible in Matlab and I misunderstood the documentation. Either way, I still need to add this additional information to my files.

  9 Comments

YT
on 12 Feb 2019
Well you're right that the UnknownTags contains the comment data but it's annoying that for some reason it's filled with spaces. Also, I'm not sure what the other tag is supposed to be.
>> tmp = struct2cell(x.UnknownTags);
>> char(tmp{3,1})
ans =
'H E L L O W O R L D '
>> char(tmp{3,2}) %tmp{3,2} = [28 234 0 0 0 8 0 ... 0] (1x2060)
ans =
'ê ' %cut off most spaces to fit on screen
I got a bit sidetracked here, but there's still no solid explanation to why the comments written using imwrite are not showing up outside Matlab.
Walter Roberson
on 12 Feb 2019
28 234 is 1c ea in hex. If we assume Little Endian then 0Xea1c which appears to be a Microsoft patented (!!) WindowsPadding tag. Basically it is space reserved in the file in anticipation that you might add more tags.
Walter Roberson
on 12 Feb 2019
My guess is that the comments were stored as UTF16, probably little endian. Do the numeric values alternate 32 and something useful or do they alternate 0 and something useful like would be the case for utf16?

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1 Answer

Rik
Answer by Rik
on 10 Feb 2019

For my FEX submission PhotoAnnotation I bypass the built-in tools in favor of exiftool.
URL=['http://web.archive.org/web/20170820125224if_/',...
'https://www.sno.phy.queensu.ca/~phil/exiftool/exiftool-10.61.zip'];
urlwrite(URL,[folderpath 'exiftool.zip']);
You can either canibalize some functions I use in my GUI, or go through its documentation yourself. (I have no clue anymore how it works outside of my specific work flow, which I would say is both the upside and the downside of modular programming.)

  2 Comments

YT
on 10 Feb 2019
Well exiftool seems easy to use (from the lines I've seen in your function) but I don't really want to use another tool besides Matlab.
Rik
on 11 Feb 2019
Of course that is your decision to make. At least you have a backup method in case you don't get the pure-Matlab method to work.
For me exiftool was the better fit, as I wanted to use the same function in Octave as well, and the comment writing is not (yet?) implemented. (Or at least in the version I was using when writing PA)

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