How to preserve image metadata in MATLAB imwrite? - matlab

Question

I want to preserve image metadata but my code strips all metadata. How do I stop this? I run this script from the MATLAB SDE command prompt. Code is below:
p = which('G0011363.JPG');
filelist = dir([fileparts(p) filesep '*.JPG']);
fileNames = {filelist.name};
fileNames_size = size(fileNames,2);
number_of_colums = fileNames_size;
for k = 1:number_of_colums
imwrite(undistortImage(imread(fileNames{k}), cameraParams2cof, 'OutputView', 'valid'), (strcat(int2str(k), 'R2_3COF_ONRcorrected.jpg')));
end

Answer 1

You can read in metadata using imfinfo, and you can write specific metadata to your image file with imwrite (as long as the particular tag is supported) as key/value pairs. Look at help imwrite for more info.
Example:
>> I = imread('NeverGonnaGiveYouUp.png');
>> imwrite(I, 'output.png', 'png','Author','Rick Astley');
>> Iinfo = imfinfo('output.png');
>> Iinfo.Author
ans =
Rick Astley

Answer 2

I found a solution, but it isn't perfect...
Note: The posted solution applies Windows OS.
Where referring to image metadata, I assume you mean Exif data.
According to https://www.mathworks.com/matlabcentral/answers/152559-writing-exif-data-to-jpg
Unfortunately, there is currently no off-the-shelf functionality to write EXIF data to an image file in MATLAB. You can only read EXIF data from an image file ( exifread and imfinfo ).
You can use run_exiftool do copy Exif data from one image to another:
Download and extract exiftool-10.25.zip
Copy file exiftool(-k).exe to your working folder, and rename file to exiftool.exe
Download run_exiftool from https://www.mathworks.com/matlabcentral/fileexchange/42000-run-exiftool, Copy getexif.m and putexif.m to your working folder.
Try the following code sample:
%Copy the file from c:\Program Files\MATLAB\R2014b\mcr\toolbox\matlab\demos\ to local folder.
%Note: ngc6543a.jpg is part of Matlab installation.
copyfile([matlabroot, '/mcr/toolbox/matlab/demos/ngc6543a.jpg'], cd);
%Read image
I = imread('ngc6543a.jpg');
%Save I to myfile.jpg and add Exif data of ngc6543a.jpg to myfile.jpg
status = putexif(I, 'myfile.jpg', 'ngc6543a.jpg');
%Read Exif data from ngc6543a.jpg
[ngc6543a_exifdata, ngc6543a_nf] = getexif('ngc6543a.jpg');
%Read Exif data from myfile.jpg
[myfile_exifdata, myfilenf] = getexif('myfile.jpg');
I am getting a warning message: Warning: Exif tags may not have been copied, but it seems to work.
Result:
>> ngc6543a_exifdata
ngc6543a_exifdata =
ExifToolVersion : 10.25
FileName : ngc6543a.jpg
Directory : .
FileSize : 27 kB
FileModifyDate : 2014:07:27 12:00:28+03:00
FileAccessDate : 2016:08:14 17:42:23+03:00
FileCreateDate : 2016:08:14 17:18:27+03:00
FilePermissions : rw-rw-rw-
FileType : JPEG
FileTypeExtension : jpg
MIMEType : image/jpeg
JFIFVersion : 1.01
ResolutionUnit : None
XResolution : 1
YResolution : 1
Comment : CREATOR: XV Version 3.00b Rev: 6/15/94 Quality = 75, Smoothing = 0.
ImageWidth : 600
ImageHeight : 650
EncodingProcess : Baseline DCT, Huffman coding
BitsPerSample : 8
ColorComponents : 3
YCbCrSubSampling : YCbCr4:2:0 (2 2)
ImageSize : 600x650
Megapixels : 0.390
>> myfile_exifdata
myfile_exifdata =
ExifToolVersion : 10.25
FileName : myfile.jpg
Directory : .
FileSize : 75 kB
FileModifyDate : 2016:08:14 18:08:51+03:00
FileAccessDate : 2016:08:14 18:08:51+03:00
FileCreateDate : 2016:08:14 17:40:22+03:00
FilePermissions : rw-rw-rw-
FileType : JPEG
FileTypeExtension : jpg
MIMEType : image/jpeg
JFIFVersion : 1.01
ResolutionUnit : None
XResolution : 1
YResolution : 1
Comment : CREATOR: XV Version 3.00b Rev: 6/15/94 Quality = 75, Smoothing = 0.
ImageWidth : 600
ImageHeight : 650
EncodingProcess : Baseline DCT, Huffman coding
BitsPerSample : 8
ColorComponents : 3
YCbCrSubSampling : YCbCr4:2:0 (2 2)
ImageSize : 600x650
Megapixels : 0.390