This function only support JPEG file.
https://github.com/Imagick/imagick/issues/124#issuecomment-226942140
(PECL imagick 2, PECL imagick 3)
Imagick::commentImage — Adds a comment to your image
comment
The comment to add
Returns true
on success.
Throws ImagickException on error.
Example #1 Using Imagick::commentImage():
Commenting an image and retrieving the comment:
<?php
/* Create new Imagick object */
$im = new imagick();
/* Create an empty image */
$im->newImage(100, 100, new ImagickPixel("red"));
/* Add comment to the image */
$im->commentImage("Hello World!");
/* Display the comment */
echo $im->getImageProperty("comment");
?>
This function only support JPEG file.
https://github.com/Imagick/imagick/issues/124#issuecomment-226942140