Carrierwave and mini_magick finding widths & height - ruby-on-rails

Question

After a bit of investigation I decided to use Carrierwave and mini_magick on my new rail3 app.
I've set it up and it works perfectly. However I have a one question. I'd like to be able to access the width and height, so I can form the html correctly. However, there is no default data from which to get this information. Because of the way it stores the data I'm I cannot think of any way that I can add it to the database.
Can anyone suggest any tips or ideas? Is it even possible?

Answer 1

class Attachment
mount_uploader :file, FileUploader
def image
#image ||= MiniMagick::Image.open(file.path)
end
end
And use it like this:
Attachment.first.image['width'] # => 400
Attachment.first.image['height'] # => 300

Answer 2

Just for record, I have used a similar solution, however using files with Mongo GridFS, here it goes:
def image
#image ||= MiniMagick::Image.read(Mongo::GridFileSystem.new(Mongoid.database).open(file.path, 'r'))
end

Answer 3

Disadvantage of calculating Image height / width using RMagick or MiniMagick in run time:
Its CPU intensive
It requires Internet to get image and calculate the dimensions.
Its a slow process
FYI You can also calculate the Image Height, Width after the
Image is fully loaded by using the load event associated with the
<img> tag with the help of jQuery.
For Example:
$(document).ready(function(){
var $image = $('.fixed-frame img');
$image.load(function(){
rePositionLogo($image);
});
if($image.prop('complete')){
rePositionLogo($image);
}
});
function rePositionLogo($image){
var height = $image.height();
var width = $image.width();
if (width > height) {
$image.parents('.header').addClass('landscape');
var marginTop = (105 - $image.height())/2;
$image.css('margin-top', marginTop + 'px')
}else{
$image.parents('.header').addClass('portrait');
}
}
Be careful, because load() will not trigger when an image is already loaded. This can happens easily when an image is in the user's browser cache.
You can check if an image is already loaded using $('#myImage').prop('complete'), which returns true when an image is loaded.

Answer 4

I think the best way is to store the image dimensions in the model (database).
In my case, the model name is attachment. Then I created a migration:
rails g migration add_dimensions_to_attachments image_width:integer image_height:integer
After that, run the migration:
rake db:migrate
In my Image Uploader file app/uploaders/image_uploader.rb, I have:
class ImageUploader < CarrierWave::Uploader::Base
include CarrierWave::MiniMagick
process :store_dimensions
private
def store_dimensions
if file && model
model.image_width, model.image_height = ::MiniMagick::Image.open(file.file)[:dimensions]
end
end
end
With this, the image dimensions is saved in the upload step.
To get the dimensions, I simply run attachment.image_width or attachment.image_height
See the reference here.