Rails Carrierwave Base64 image upload

Question

What is the best way to upload an image from a client to a Rails backend using Carrierwave. Right now our iOS developer is sending in the files as base64, so the requests come in like this:

"image_data"=>"/9j/4AAQSkZJRgABAQAAAQABAAD/4QBYRXhpZgAATU0AKgAAAAgAAgESAAMAAAABAAEAAIdpAAQAAAABAAAAJgAAAAAAA6ABAAMAAAABAAEAAKACAAQAAAABAAAAHqADAAQAAAABAAAAHgAAAAD/2wBDAAEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQH/2wBDAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQH/wAARCAAeAB4DAREAAhEBAxEB/8QAHwAAAQUBAQE....

So, my question is really two questions. Should I tell him to send in a different file format? If base64 is the right way to send these files in, then how do I deal with them in carrierwave?

Answer 1

I think that one solution can be to save the decoded data to file and then assign this file to mounted uploader. And after that get rid of that file.

The other (in-memory) solution can be this one:

# define class that extends IO with methods that are required by carrierwave
class CarrierStringIO < StringIO
  def original_filename
    # the real name does not matter
    "photo.jpeg"
  end

  def content_type
    # this should reflect real content type, but for this example it's ok
    "image/jpeg"
  end
end

# some model with carrierwave uploader
class SomeModel
  # the uploader
  mount_uploader :photo, PhotoUploader

  # this method will be called during standard assignment in your controller
  # (like `update_attributes`)
  def image_data=(data)
    # decode data and create stream on them
    io = CarrierStringIO.new(Base64.decode64(data))

    # this will do the thing (photo is mounted carrierwave uploader)
    self.photo = io
  end

end

Answer 2

You can easily achieve that using Carrierwave-base64 Gem you don't have to handle the data yourself, all you do is add the gem and change your model from

mount_uploader :file, FileUploader

to

mount_base64_uploader :file, FileUploader

and thats it, now you can easily say:

Attachment.create(file: params[:file])

Answer 3

Old question but I had to do a similar thing, upload image from base64 string which was passed on via a json request. This is what I ended up doing:

#some_controller.rb
def upload_image
  set_resource
  image = get_resource.decode_base64_image params[:image_string]
  begin
    if image && get_resource.update(avatar: image)
      render json: get_resource
    else
      render json: {success: false, message: "Failed to upload image. Please try after some time."}
    end
  ensure
    image.close
    image.unlink
  end
end

#some_model.rb
def decode_base64_image(encoded_file)
  decoded_file = Base64.decode64(encoded_file)
  file = Tempfile.new(['image','.jpg']) 
  file.binmode
  file.write decoded_file

  return file
end