PDF Previews with carrierwave

file_uploader.rb

class ItemUploader < CarrierWave::Uploader::Base
  require 'carrierwave/orm/activerecord'
  include CarrierWave::RMagick
  
  attr_reader :geometry

  # Create thumbnail for images and PDFs
  version :thumb, :if => :thumbable? do
    process :resize_to_fit => [240, 240], :if => :image?
    process :pdf_preview => [240, 240], :if => :pdf?
    process :get_geometry
    # handles cases where fog misses the content type
    process :set_content_type

    # We need to change the extension for PDF thumbnails to '.jpg'
    def full_filename(filename)
      filename = File.basename(filename, '.pdf') + '.jpg' if File.extname(filename)=='.pdf'
      "thumb_#{filename}"
    end
  end

  def pdf_preview(width, height)
    # Read in first page of PDF and resize ([0] -> read the first page only)
    image = ::Magick::Image.read("#{current_path}[0]").first
    image.resize_to_fill!(width, height, ::Magick::NorthGravity)
    # Most PDFs have a transparent background, which becomes black when converted to jpg.
    # To override this, we must create a white canvas and composite the PDF onto the convas.
    # First check the image backgrounf color.
    # #FFFFFFFFFFFF0000 is how ImageMagick defines transparent
    if image.background_color != "#FFFFFFFFFFFF0000"
      # Create a blank canvas
      canvas = ::Magick::Image.new(image.columns, image.rows) { self.background_color = "#FFF" }
      # Merge PDF thumbnail onto canvas
      canvas.composite!(image, ::Magick::CenterGravity, ::Magick::OverCompositeOp)
      # Save as .jpg. We need to change the file extension here so that the fog gem picks it up and
      # sets the correct mime type. Otherwise the mime type will be set to PDF, which confuses browsers.
      canvas.write("jpg:#{current_path}")
    else
      # If the imag ebackground color is transparent we don't need to worry about the canvas.
      image.write("jpg:#{current_path}")
    end
    file.move_to File.basename(filename, '.pdf') + '.jpg'
    # Free memory allocated by RMagick which isn't managed by Ruby
    image.destroy!
    canvas.destroy! unless canvas.nil?
  rescue ::Magick::ImageMagickError => e
    Rails.logger.error "Failed to create PDF thumbnail: #{e.message}"
    raise CarrierWave::ProcessingError, "is not a valid PDF file"
  end
  
  def set_content_type(*args)
    self.file.instance_variable_set(:@content_type, "image/jpeg")
  end

  private

    def thumbable?(file)
      image?(file) || pdf?(file)
    end

    def image?(file)
      file.content_type.include? 'image'
    end

    def pdf?(file)
      file.content_type == 'application/pdf'
    end

    def get_geometry
      if (@file)
        img = ::Magick::Image::read(@file.file).first
        @geometry = { :width => img.columns, :height => img.rows }
      end
    end
end

Nice article.. is there any possibility the ppt file also to convert to thumbnail

Not sure I follow

Ok, is there any gem file to convert the ppt, doc, excel to ppt and show it

Pls help me if we upload zip file then how to show the zip icon using carrierwave gem.

Sorry @NRavindra90 it's been a while since I worked with CarrierWave, been using ActiveStorage for everything recently, not sure I can help much here.

Sorry for disterub you, I am new for rails so I am asking you. I am stuck in middle in my work.Is there possibility to use the active storage like any gems to create a thumbnail as first page of. ppt, pdf, doc, excel . Thanks

Yes, ActiveStorage has the ability to make previews of the first page of pdf's (and videos) and you can write your own previewer for other file types too

I did it using poppler gem but no luck .