Something broke in modx thumbnails, phpthumb, on certain images.

Recently I've noticed that some thumbnails are now not generating and if I use pthumb snippet on the public site the page will not display. After downloading and re-saving the files using Photoshop save for web and then uploading again they work fine. It seems to me that these files have a color profile or something else in the jpg format that causes the thumbnail generation to fail. The following error shows up over and over in the logs:

[2018-08-31 14:43:28] (ERROR @ /home/folder/core/model/phpthumb/modphpthumb.class.php : 156) Error outputting thumbnail:
OutputThumbnail() failed because !is_resource($this->gdimg_output) in file "phpthumb.class.php" on line 618

We have ImageMagik installed on the system so I don't know why gd would come into play. Has anybody else experienced this? I do not know if it is a server configuration (standard cPanel easyApache PHP packages) or if it is an issue introduced in MODX 2.6.5. [ed. note: pyrographics last edited this post 5 years, 7 months ago.]

Check permissions on the assets directory as this fixed a similar issue for me. It should be 755.
Is there anything in the error log?
Is it happening on newly uploaded images only?

Quote from: 9thwave at Sep 05, 2018, 08:46 AM

Check permissions on the assets directory as this fixed a similar issue for me. It should be 755.
Is there anything in the error log?
Is it happening on newly uploaded images only?

Permissions check is the first thing I did. This is an older site that was working fine prior to the recent updates and no permissions were changed.

Error log shows the error in my initial post.

Happens on images uploaded prior to the recent updates, newly uploaded images do not necessarily have the issue but if I download and then re-upload the same image in another directory the thumbnail still does not generate correctly.

Changing the PHP version back from 7.2 to 5.6 causes the thumbnail errors to go away but the installed extensions are the same for both versions.