Drupal 6 image errors and solutions (ImageCache, ImageField, CCK)

After just creating another Drupal 6 website that uses ImageCache, ImageAPI, ImageToolkit, CCK, and ImageField, I thought I'd make some notes here about the problems I ran into when trying to use ImageField with CCK to let users upload images to my website. I encountered several very frustrating errors along the way, and here are my notes related to those errors.

Note: This blog post is about Drupal 6. Things have changed quite a bit in Drupal 7, and these tips are not likely to be helpful there.

Image thumbnails not created - Problem 1

The first problem I had where image thumbnails were not created was a repeat of an old problem I forgot and then remembered. In short, the ImageAPI GD2 module must be enabled for this to even have a chance of working. To fix this problem, go to admin/build/modules and enable that module.

Image thumbnails not created - Other problems

Every other problem I had where thumbnails and other scaled images weren't created was related to one filesystem problem or another. Some of the problems were filesystem permission problems, where Drupal couldn't write to (a) its temporary directory or (b) the final destination directory for the scaled images (somewhere under sites/files). A third problem happened when I went live, and my Drupal temporary directory on my Development system was not the same as my temporary directory on the Production system, so again, creating thumbnail images and scaled images failed dramatically.

FWIW, the really frustrating part of this is not having good error messages. When these modules work, they are really outstanding additions to Drupal, but when they don't work, you don't get any meaningful ImageCache error messages on your web pages, and the ones you get in the Drupal reports (admin/reports/dblog) are not detailed enough to be of any help. A message like "Failed generating an image from java-string-array.jpg using imagecache preset limitimagewidth" doesn't help; I already knew that. What I need to know is "Why did it fail?"

Drupal ImageCache, ImageField, CCK module problems and notes

Now that I got that off my chest, here are my notes. I created these notes as I was trying down Drupal file path problems related to images, thumbnails, scaled and cropped images, and so on, but hopefully they'll be helpful in general Drupal image problem troubleshooting.

ImageCache module
You can create 'presets' here, like my '530px_wide' preset, which scales every image down to 530px wide. All the image-editing actions are available here, including scale, crop, and so on. You can also Flush your images here. There are no file path settings here.
The only option here is to set JPEG Quality.
You can again set JPEG Quality (I don't know how this works with ImageToolkit), crop background, and set interlacing.
Drupal Filesystem settings
Under the Drupal Filesystem menu (admin/settings/file-system) you can set the Drupal Filesystem Path and Temporary Directory. On my Development system my temporary directory was a MAMP directory, and in Production it needed to be a vastly different directory. IMHO, this setting needs to be stored in a configuration file, and not in the database. Hopefully this has been corrected in Drupal 7.
ImageAPI GD2 module
As mentioned earlier, in admin/build/modules, the ImageAPI GD2 module needs to be enabled, or you're not going to get any thumbnails, scaled, or cropped images at all. Again, I don't see any error messages in the Drupal error logs that will help you see this.
CCK, ImageField, and new Content Types
If you use CCK to create a new Content Type, and that Content Type uses an ImageField, there is a file path setting in your ImageField field. There are many other image settings here as well, including Filesize Restrictions, Alt Text, Title Text, Image Resolution, Image Types, and so on.

Drupal image problems, errors, and notes - Summary

I hope this list of basic information about the Drupal image modules (ImageAPI, ImageCache, ImageField, ImageToolkit) and the errors you can get in trying to generate thumbnail images, scaled images, cropped images, and so on is helpful. Next week I'll be creating another Drupal website that will again use CCK, Views, and all these image modules, and I'll update these notes when I create that website.

Until then, if you're having problems generating thumnails and scaled and cropped images in Drupal, (a) make sure the GD2 module is enabled, and (b) re-check all those filesystem/filepath settings. That's where all my problems were. You can also check the Drupal reports for error messages, but as of this writing on June 6, 2011, they were not very helpful.