How to force all upload to jpegs? (currently using the deprecated processing gem)

[justintanner]

Loving shrine, thanks so much for all your work.

I've got a hack to force all non-jpeg uploads to be converted to jpeg:

class ImageUploader < Shrine
  # Converts all images to jpegs
  process(:store) do |io, context|
    original = io.download
    mime_type = context.try(:[], :record)&.file_data.try(:[], "metadata").try(:[], "mime_type")

    if mime_type != "image/jpeg" || mime_type != "image/jpg"
      # How can we force transparent backgrounds to save as white and not black?
      jpeg = ImageProcessing::Vips
               .source(original)
               .convert("jpeg")
               .saver(quality: 85)
               .call

      original.close

      jpeg
    else
      original.close

      io
    end
  end

  Attacher.derivatives do |original|
    vips = ImageProcessing::Vips.source(original)

    Image::SIZES.transform_values do |dimensions|
      vips.resize_to_limit!(dimensions.first, dimensions.second)
    end
  end
end

I noticed the deprecation warning after deploying this solution, but I see no way to accomplish this using the derivatives plugin.

Any way to avoid using the processing gem? or alternative ways to accomplish the same thing?