Image dimensions validation with carrierwave-vips

Image_dimensions_validation_with_carrierwave_vips.rb

require 'vips'
class Photo < ActiveRecord::Base
    # Include the VIPS moduel in model so we have access to the `Image` class
    include VIPS
    # Basic attributes
    attr_accessible :image, :image_cache, :crop_x, :crop_y, :crop_w, :crop_h
    # mount Carrierwave 
    mount_uploader :image, PhotoUploader
    # Call the minimum_dimensions method on validation
    validate :minimum_dimensions
    # Crop the photo if we need to
    after_update :crop_image
    # Minimum dimensions validation method
    def minimum_dimensions
        # Check to make sure we've got a file and nothing sketchy is going on
        if self.image.file
            # Read the image's path
            file_path = self.image.file.path
            # Use VIPS to read the image
            image = Image.new(file_path)
            # Add an error message specifying the minimum dimensions,
            # if the image.x_size (width) or image.y_size is less than 400 pixels
            # simply change the value if you need different minimums
            errors.add(:image, "must be at least 400 x 400 pixels") if image.x_size < 400 or image.y_size < 400
        end
        # Voila done!
    end
    def set_crop_and_rotate_parameters(x, y, w, h, rotation)
        @crop_x = x
        @crop_y = y
        @crop_w = w
        @crop_h = h
        @rotate = rotation
    end
    def crop_image
        image.recreate_versions! if crop_x.present?
    end
end