Reading the Comment
[edit]On Windows
[edit]On Mac
[edit]On Linux
[edit]Open a shell and type
jpegtopnm -comments image1.jpeg > /dev/null
The comment of the image file image1.jpeg is written to standard error. In order to find the comment of a PNG file, type
pngtopnm -text commentfile image1.png > /dev/null
The comment is written into the file commentfile.
To read comments added in a jpeg file, use the command line tool rdjpgcom.
rdjpgcom -verbose image_with_comment.jpeg
Writing a Comment
[edit]On Windows
[edit]for testing only
On Mac
[edit]On Linux
[edit]PPM file to JPEG file
[edit]Open a shell and type
pnmtojpeg -comment "Author: Emma Peel; Licence: Attribution-ShareAlike 1.0" image1.ppm > image1.jpeg
Thus, the new JPEG file image1.jpeg with the above comment is created from the PPM file image1.ppm.
PPM file to PNG file
[edit]In order to create a PNG file with comment you first need to create a comment file in the format
Key1 Value1 Key2 Value2 Key3 Value3 . .
Assumed we had a file called comment-file with the following contece:
#>cat comment-file Author: Emma Peel Licence: Attribution-ShareAlike 1.0 #>
we create the new PNG file by typing
pnmtopng -text comment-file image1.ppm > image1.png
Add comment to existing JPEG files
[edit]The command line tool 'wrjpgcom' can be used to add comments to existing JPEG files.
Open a shell and type
wrjpgcom -comment "Author: Emma Peel; Licence: Attribution-ShareAlike 1.0" image1.jpeg > image_with_comment.jpeg
If there is an existing comment block (even an empty one) in the JPEG file, you must add the option '-replace' for this to work:
wrjpgcom -replace -comment "Author: Emma Peel; Licence: Attribution-ShareAlike 1.0" image1.jpeg > image_with_comment.jpeg
Please refer to the man page for more details.