active_storage.md

official guide

Basics

class User < ApplicationRecord
 has_one_attached :avatar
 has_many_attached :documents
end

Processing images (variants)

In order to do image processing you need to include MiniMagic gem

# Gemfile
# ...
gem 'mini_magick'
# ...

MiniMagic is a Ruby library that delegates commands to C program ImageMagic. So it's Rails > ActiveStorage > MiniMagic > ImageMagic

Therefore you need to have imagemagic installed !

resize to scale variant

<%= image_tag user.avatar.variant(resize: "200x150>") %>

Maning if I upload image 1000x500 I want it to be scaled up to 200x150 maning the end image will be 200x100 px

resize to fit (crop image to fit) variant

In Rails official guild you may find example:

<%= image_tag user.avatar.variant(resize_to_fit: [200, 150]) %>

Maning if I upload image 1000x500 I want it to be scaled to 333X100 and then croped to fit 200x100 px

This will not work in Rails 5.2 due to reason described here

Active Storage 5.2 still uses MiniMagick directly, so there are no #resize_* macros available there. The ImageProcessing addition to Active Storage was merged after 5.2 was released, so it's currently available only on GitHub and will be released in Active Storage 6.0. The mogrify command indicates that MiniMagick::Image class is used, as ImageProcessing gem uses convert.

workaround while ActiveStorage 6 is released:

head_image.variant(combine_options: {
  auto_orient: true,
  gravity: "center",
  resize: "200x150^",
  crop: "200x150+0+0"})

representation

• https://api.rubyonrails.org/classes/ActiveStorage/Variation.html

• [representation](https://api.rubyonrails.org/classes/ActiveStorage/Blob/Representable.html#method-i-variant

• https://github.com/rails/rails/blob/b2eb1d1c55a59fee1e6c4cba7030d8ceb524267c/activestorage/app/controllers/active_storage/representations_controller.rb

• rails/rails#35028

blob.representation(resize: "100x100").processed.service_url

active storage direct upload to AWS S3

<?xml version="1.0" encoding="UTF-8"?>
<CORSConfiguration xmlns="http://s3.amazonaws.com/doc/2006-03-01/">
<CORSRule>
    <AllowedOrigin>*</AllowedOrigin>
    <AllowedMethod>GET</AllowedMethod>
    <MaxAgeSeconds>3000</MaxAgeSeconds>
    <AllowedHeader>Authorization</AllowedHeader>
</CORSRule>
<CORSRule>
    <AllowedOrigin>https://www.sajtka.com</AllowedOrigin>
    <AllowedMethod>PUT</AllowedMethod>
    <MaxAgeSeconds>3000</MaxAgeSeconds>
    <AllowedHeader>*</AllowedHeader>
</CORSRule>
</CORSConfiguration>

To allow only certain file types (source)

   <AllowedOrigin>https://app.pobble.com</AllowedOrigin>
    <AllowedMethod>GET</AllowedMethod>
    <AllowedMethod>POST</AllowedMethod>
    <AllowedMethod>PUT</AllowedMethod>
    <ExposeHeader>Accept-Ranges</ExposeHeader>
    <ExposeHeader>Content-Range</ExposeHeader>
    <ExposeHeader>Content-Encoding</ExposeHeader>
    <ExposeHeader>Content-Length</ExposeHeader>
    <ExposeHeader>Access-Control-Allow-Origin</ExposeHeader>
    <AllowedHeader>*</AllowedHeader

rails/rails#30723

sources

• https://edgeguides.rubyonrails.org/active_storage_overview.html

• https://docs.aws.amazon.com/AmazonS3/latest/dev/cors.html

• https://aws.amazon.com/premiumsupport/knowledge-center/s3-allow-certain-file-types/

• https://github.com/equivalent/s3_bunny

Other articles

• https://mikerogers.io/2018/11/03/configuring-cors-on-s3-for-activestorage.html

custom validations

class Medium < ApplicationRecord
  has_one_attached :image

  validate :main_image_format

  def main_image_format
    return unless image.attached?
    return if image.blob.content_type.in?(['image/jpeg', 'image/png'])
    #image.purge_later
    errors.add(:image, 'needs to be an PNG or JPEG image')
  end