file_copy in core/includes/file.inc

Copies a file to a new location and adds a file record to the database.

file_file_access in core/modules/file/file.module

Implements hook_file_access().

file_move in core/includes/file.inc

Moves a file to a new location and update the file's database entry.

file_save_data in core/includes/file.inc

Saves a file to the specified destination and creates a database entry.

template_preprocess_user_picture in core/modules/user/user.theme.inc

Process variables for user-picture.tpl.php.

views_handler_field_user_picture::render in core/modules/user/views/views_handler_field_user_picture.inc

Render the field.