Ruby on Rails: How to Check If a File Is an Image

Ruby on Rails: How do you check if a file is an image?

I would use the ruby-filemagic gem which is a Ruby binding for libmagic.

How to detect a file type in a Rails app?

I guess (is not a good thing to let other people guess what you should already provided in your question) you have a model Document and your uploader is media, something like this:

class Document < ActiveRecord::Base
  mount_uploader :media, MediaUploader
end

If this is the case, for each document you get the extension (document.media.file.extension.downcase) and compare it with 'jpg', 'jpeg', 'png'

<% document.each do |doc| %>
  <% if ['jpg', 'jpeg', 'png'].include?(document.media.file.extension.downcase) %>
    <%= link_to image_tag(doc.media_url(:thumb)) %>
  <% else %>
    <%= link_to doc.media.path %> # This link downloading the file 
  <% end %>
<% end %>

Carrierwave can give you the content type if you want it by using:

document.media.content_type # this returns image/png for a png file ...

Edit:

I think a better way is to check it like this (it's cleaner):

<% document.each do |doc| %>
  <% if document.media.content_type =~ /image/ %>
    <%= link_to image_tag(doc.media_url(:thumb)) %>
  <% else %>
    <%= link_to doc.media.path %> # This link downloading the file 
  <% end %>
<% end %>

Verifying a remote image is actually an image file in ruby?

I would check to see if the service returns the proper mime types in the Content-Type HTTP header. (here's a list of mime types)

For example, the Content-Type of the StackOverflow homepage is text/html; charset=utf-8, and the Content-Type of your gravatar image is image/png

To check the Content-Type header for image in ruby using Net::HTTP, you would use the following:

def remote_file_exists?(url)
    url = URI.parse(url)
    Net::HTTP.start(url.host, url.port) do |http|
      return http.head(url.request_uri)['Content-Type'].start_with? 'image'
    end
end

How to know if an image has been uploaded or not? - Paperclip

When you added Paperclip to your model you added paperclip specific rows, mine are

cover_file_name
cover_content_type
cover_file_size
cover_updated_at

Then I check whether it is nil or not

 Foo_Class.cover_file_name.nil? 

check If images exists in rails

Write a helper method in application_helper.rb:

def print_image(url)
  url = Rails.application.assets.find_asset(url).nil? ? nil : url
  image_tag url || 'default_image.jpg'
end

Then in your view, use this:

<%= print_image(pco.printable_photo.url(:small)) %>

Try to avoid writing logic in your view. Take the help of view helpers.

How to check if image is available in ruby?

Why not just testing if the file exists?

stu_image ="/admin_num.jpg"
FileTest.exists?(RAILS_ROOT + stu_image ) #  < rails 3.0
FileTest.exists?(Rails.root + stu_image ) # >= rails 3.0

How to check if image exists in Rails?

You can use File.exist?.

if FileTest.exist?("#{RAILS_ROOT}/public/images/#{img}")
  image_check = image_tag("#{img}",options)
else
  image_check = image_tag("products/noimg.gif", options)
end

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