I've had the same problem. This is a little method I wrote to go and re-generate the whole lot, including resizing to new thumbnails, and correcting other issues like corrupt parent image sizes.
Hope it helps!
Sam,
@samotage
def self.rebuild_thumbnails
images = UserUpload.find(:all)
processed = 0
not_processed = 0
puts "---------------------------------"
puts "rebuilding thumbnails"
puts " "
images.each do |image|
this_type = image.type.to_s
puts "processing upload: #{image.id} of type: #{this_type}"
if image.thumbnailable?
puts "bingo! It's thumbnailable, now rebuilding."
image.thumbnails.each { |thumbnail| thumbnail.destroy }
puts "Re-generating main image witdh and height"
image.save
puts "Regenerating thumbnails..."
image.attachment_options[:thumbnails].each { |suffix, size| image.create_or_update_thumbnail(image.create_temp_file, suffix, *size) }
processed += 1
puts "Now processed #{processed} images"
puts ""
else
not_processed += 1
end
end
return processed
end