Previewing PDF attachments in index tables

[hasarindaKI]

• If an attachment is representable? we render the attachment as an image tag
• representable? can be true for the following types if their related tools are installed on the system
  • PDF
    • If the system has poppler installed -> PopplerPDFPreviewer or
    • If the system has muPDF installed -> MuPDFPreviewer
  • Video
    • If the system has ffmpeg installed -> VideoPreviewer
• If either poppler or muPDF is installed(Or even for video), we need to create the image_tag as given below..

blob.preview(resize_to_limit: [100, 100])

For more details => https://api.rubyonrails.org/v7.0.8/classes/ActiveStorage/Preview.html & https://api.rubyonrails.org/v7.0.8/classes/ActiveStorage/Blob/Representable.html

Proposed change

if value.try(:representable?)
    if value.try(:variable?)
        image_tag( @variant.nil? ? value : value.variant(@variant))
    else
        image_tag(value.blob.preview(resize_to_limit: [100, 100]))
    end
elsif value.try(:attached?)
    link_to value.blob.filename, rails_blob_path(value, disposition: :attachment)
else
    ""
end

Example using Hunter & Co. app

[sfnelson]

@hasarindaKI for admin tables, I don't think that we should be doing resize operations on the fly. This could be an extremely resource-heavy interaction and provides very limited value to admins.

I think this type of flow would be more appropriate:

1. Check whether the image is representable and supports the specified variant
2. If so, show an image preview
3. If not, show a download link
   Note that the reason we're using pre-defined variants is to avoid expensive processing on page view, and shift processing to image upload instead.

[hasarindaKI]

Yes, agreed that we shouldn't be generating previews on the fly.

Instead of representable, we could use variable & show the image.

Note: variable is a include check in a configurable list of content types.