lib/imginfo.rb

   1 # Nick's web site: imginfo filter.  Generate XML representation of image
   2 # metadata which can be further processed into a web page.
   3 #
   4 # Copyright © 2020 Nick Bowler
   5 #
   6 # This program is free software: you can redistribute it and/or modify
   7 # it under the terms of the GNU General Public License as published by
   8 # the Free Software Foundation, either version 3 of the License, or
   9 # (at your option) any later version.
  10 #
  11 # This program is distributed in the hope that it will be useful,
  12 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 # GNU General Public License for more details.
  15 #
  16 # You should have received a copy of the GNU General Public License
  17 # along with this program.  If not, see <https://www.gnu.org/licenses/>.
  18
  19 class ImgInfoFilter < Nanoc::Filter
  20     identifier :imginfo
  21     type :binary => :text
  22
  23     require 'exifr/jpeg'
  24     require 'fastimage'
  25
  26     def do_variant(xml, name, item = @item, rep: :default)
  27         file = item.reps[rep].raw_path
  28         unless file.nil?
  29             w, h = FastImage.size(file)
  30             sz = File.size(file)
  31
  32             xml.variant {
  33                 xml.name(name)
  34                 xml.uri(item_uri(item, rep: rep))
  35                 xml.width(w)
  36                 xml.height(h)
  37                 xml.filesize(human_filesize(sz))
  38             }
  39         end
  40     end
  41
  42     def run(filename, params = {})
  43         exif = EXIFR::JPEG.new(filename).to_hash
  44
  45         b = Nokogiri::XML::Builder.new do |xml|
  46             xml.image {
  47                 do_variant(xml, "Large", rep: :large)
  48                 do_variant(xml, "Medium", rep: :medium)
  49                 do_variant(xml, "Original")
  50
  51
  52                 if @item[:description]
  53                     xml.description(:xmlns => 'http://www.w3.org/1999/xhtml') {
  54                         xml << @item[:description]
  55                     }
  56                 end
  57
  58                 xml.exif {
  59                     exif.each do |key, value|
  60                         # Convert some fields to more useful forms...
  61                         case key
  62                         when :f_number, :exposure_bias_value
  63                             value = sprintf("%.1f", value)
  64                         when :focal_length
  65                             value = sprintf("%d\n", value)
  66                         when :gps_version_id
  67                             value = value.bytes.join(".")
  68                         when :exposure_program
  69                             case value
  70                             when 1 then value = "Manual"
  71                             when 2 then value = "Normal program"
  72                             when 3 then value = "Aperture priority"
  73                             when 4 then value = "Shutter priority"
  74                             end
  75                         when :metering_mode
  76                             case value
  77                             when 1 then value = "Average"
  78                             when 2 then value = "Center weighted average"
  79                             when 3 then value = "Spot"
  80                             when 4 then value = "Multi-spot"
  81                             when 5 then value = "Pattern"
  82                             when 6 then vlaue = "Partial"
  83                             end
  84                         when :flash
  85                             tmp = if value & 1 == 1 then "Yes" else "No" end
  86                             case (value >> 3) & 3
  87                             when 1, 2 then tmp += ", compulsory"
  88                             when 3 then tmp += ", auto"
  89                             end
  90                             case (value >> 1) & 3
  91                             when 2 then tmp += ", return light not detected"
  92                             when 3 then tmp += ", return light detected"
  93                             end
  94                             value = tmp
  95                         end
  96
  97                         case value
  98                         when String
  99                             value.delete!("\x00")
 100                             value.strip!
 101                         when Time
 102                             # EXIF does not do timezones so don't display one
 103                             value = value.strftime("%Y-%m-%d %H:%M:%S")
 104                         end
 105
 106                         xml.send((key.to_s << "_").to_sym, value.to_s)
 107                     end
 108                 }
 109             }
 110         end
 111         b.to_xml
 112     end
 113 end