Module: Imogen::Iiif::Tiles

Defined in:
lib/imogen/iiif/tiles.rb

Class Method Summary collapse

Class Method Details

.for(img, dest_dir, format = :jpg, tile_size = 128, quality = 'default') {|image, suggested_dest_path_for_tile, format, raster_opts| ... } ⇒ Object

Yields many times, for each set of iiif tile raster opts for the given image.

Parameters:

  • img (Image) —

    The image to be analyzed.

  • dest_dir (String) —

    The target output directory for the tile subdirectory hierarchy.

  • format (String) (defaults to: :jpg) —

    Tile format

  • tile_size (Integer) (defaults to: 128) —

    Tile size

  • quality (String) (defaults to: 'default') —

    IIIF quality value (e.g. ‘color’, ‘default’)

Yields:

  • (image, suggested_dest_path_for_tile, format, raster_opts) —

    Image and tile generation info



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# File 'lib/imogen/iiif/tiles.rb', line 18

def self.for(img, dest_dir, format = :jpg, tile_size = 128, quality = 'default')
  format = :jpg if format.to_s == 'jpeg'

  width = img.width
  height = img.height

  # For this implementation, we will only support square tiles (same width and height)
  tile_width = tile_size
  tile_height = tile_size

  # If the original image dimensions are smaller than the tile_size,
  # generate a tile for region 'full' and size 'full'.
  if width < tile_size && height < tile_size
    raster_opts = {
      region: 'full',
      size: 'full',
      rotation: 0,
      quality: quality,
      format: format
    }

    dest_path = File.join(
      dest_dir,
      raster_opts[:region],
      raster_opts[:size],
      raster_opts[:rotation].to_s,
      "#{raster_opts[:quality]}.#{Imogen::Iiif::FORMATS[raster_opts[:format]]}"
    )
    yield(img, dest_path, raster_opts['format'], Imogen::Iiif.path_to_opts(dest_path, dest_dir))
  end


  # NOTE: Algorithm below is based on: https://iiif.io/api/image/2.1/#a-implementation-notes
  self.scale_factors_for(width, height, tile_size).each do |scale_factor|
    scale_factor_as_float = scale_factor.to_f

    col = 0
    x = 0
    while x < width
      row = 0
      y = 0
      while y < height
        # Calculate region parameters /xr,yr,wr,hr/
        xr = col * tile_width * scale_factor_as_float
        yr = row * tile_height * scale_factor_as_float
        wr = tile_width * scale_factor_as_float
        if xr + wr > width
          wr = width - xr
        end
        hr = tile_height * scale_factor_as_float
        if yr + hr > height
          hr = height - yr
        end
        # Calculate size parameters /ws,hs/
        ws = tile_width
        if xr + tile_width * scale_factor_as_float > width
          ws = (width - xr + scale_factor_as_float - 1) / scale_factor_as_float  # +scale_factor_as_floatZ-1 in numerator to round up
        end

        hs = tile_height
        if yr + tile_height * scale_factor_as_float > height
          hs = (height - yr + scale_factor_as_float - 1) / scale_factor_as_float
        end

        # If the region width (wr) or region height (hr) go negative, we've gone too far. Break!
        break if wr <= 0 || hr <= 0

        xr = xr.floor
        yr = yr.floor
        wr = wr.floor
        hr = hr.floor
        ws = ws.floor
        hs = hs.floor
        region = "#{xr},#{yr},#{wr},#{hr}"
        size = "#{ws},"

        # When tile_width and tile_height are the same, OpenSeadragon only specifies
        # the width for the size param in image slice URLs, so we will generally not
        # include the height in the size param string.
        size += "#{hs}" if tile_width != tile_height

        # Need to do this correction for OpenSeadragon Compatibility, since it asks for "full" in this case.
        region = 'full' if region == "0,0,#{width},#{height}"

        raster_opts = {
          region: region,
          size: size,
          rotation: 0,
          quality: quality,
          format: format
        }

        dest_path = File.join(
          dest_dir,
          raster_opts[:region],
          raster_opts[:size],
          raster_opts[:rotation].to_s,
          "#{raster_opts[:quality]}.#{Imogen::Iiif::FORMATS[raster_opts[:format]]}"
        )
        yield(img, dest_path, raster_opts['format'], Imogen::Iiif.path_to_opts(dest_path, dest_dir))

        row += 1
        y += tile_height
      end
      col += 1
      x += tile_width
    end
  end
end

.generate_with_vips_dzsave(img, output_dir, format: :jpeg, tile_size: 128, tile_filename_without_extension: 'default') ⇒ Object

This method should NOT be used right now because it’s missing some tiles that we rely on. This method is just here as a partial vips-dzsave-based implementation that we may want to build off in a fututure release. The Imogen::Iiif::Tiles.for method should be used instead, since it generates all of the expected tiles. The issue with this method may be related to this: github.com/libvips/libvips/discussions/2036



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# File 'lib/imogen/iiif/tiles.rb', line 135

def self.generate_with_vips_dzsave(img, output_dir, format: :jpeg, tile_size: 128, tile_filename_without_extension: 'default')
  warn "Warning: The generate_with_vips_dzsave is only partially functional and should not "\
       "be used to generate tiles yet.  If you use this method, some IIIF tiles will be missing."
  format = :jpg if format == :jpeg
  format = format.to_sym
  img.dzsave(
    output_dir,
    layout: 'iiif',
    suffix: ".tmp.#{format}",
    overlap: 0,
    tile_size: tile_size
  )

  # Update tile names with desired value
  Dir[File.join(output_dir, "**/*.tmp.#{format}")].each do |file_path|
    new_name = File.join(File.dirname(file_path), "#{tile_filename_without_extension}.#{format}")
    File.rename(file_path, new_name)
  end

  # Clean up unused additional dzsave files
  ['info.json', 'vips-properties.xml'].each do |unnecessary_file_name|
    File.delete(file_to_delete)
  end
end

.scale_factors_for(full_image_width, full_image_height, tile_size) ⇒ Object 



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# File 'lib/imogen/iiif/tiles.rb', line 5

def self.scale_factors_for(full_image_width, full_image_height, tile_size)
  largest_scale_factor = Imogen::Zoomable.max_levels_for(full_image_width, full_image_height, tile_size)
  largest_scale_factor -= Math.log2(tile_size / 2) # remove scales smaller than tile size
  (0..(largest_scale_factor.to_i)).map { |exp| 2.pow(exp) }
end