Just as the contributed
Filefield module largely handled file handling in Drupal 6, two modules
Imagecache, largely handled image handling.
Imagefield was used for attaching images to nodes, and
Imagecache was used to create derivations of those images by resizing or cropping them. This was very popular for things like creating square thumbnails in a grid for image galleries. The functionality of both modules has been brought into core for Drupal 7, along with an improved API for managing this functionality from code.
The Drupal 7 Image API provides a variety of functions to manipulate images. By default, Drupal uses the GD image management library that is included with PHP. However Drupal also offers the ...