Group Artworks into columns for a pinterest style layout (for use in emails)

gistfile1.rb

module ArtworkColumns
  # Return an array of artworks grouped together in sub arrays by being added to the shortest 'column'
  # based on a fixed width and aspect ratios.
  #
  # @param {Array} artworks The array of artworks to group into columns
  # @param {Number} num_columns The number of columns to group them into
  # @param {Number} width The width the images will be displayed at
  #
  # @return {Array} An array of artworks grouped into sub arrays by being added to the shortest one.
  def self.artwork_columns(artworks, num_columns, width)
    artwork_cols = []

    # Initialize columns
    num_columns.times do
      artwork_cols << []
    end

    artworks.each do |artwork|
      add_to_shortest_column!(artwork_cols, artwork, width) if artwork.default_image
    end

    artwork_cols
  end

  private

  # Adds artwork to shortest column
  def self.add_to_shortest_column!(artwork_cols, artwork, width)
    min_height = column_height(artwork_cols[0], width)
    min_column_idx = 0

    artwork_cols.each_with_index do |column, idx|
      height = column_height(column, width)
      if height < min_height
        min_height = height
        min_column_idx = idx
      end
    end

    artwork_cols[min_column_idx] << artwork
  end

  # Calculate sum of heights of artworks in column
  def self.column_height(artwork_col, width)
    height = 0
    artwork_col.each do |artwork|
      if (aspect_ratio = artwork.default_image.aspect_ratio)
        height += (width / aspect_ratio).floor
      else
        height += width
      end
    end
    height
  end

  # Calculate sun of widths of artworks in row
  def self.calculate_width(artwork_row, height)
    width = 0
    artwork_row.each do |artwork|
      if (aspect_ratio = artwork.default_image.aspect_ratio)
        width += (height * aspect_ratio).ceil
      else
        width += height
      end
    end
    width
  end

  # calculate height of each artwork in collection to sum up to width
  def self.calculate_max_height_for_width(artworks, width)
    calculated_width = 0
    height = 0
    while calculated_width <= width
      height += 1
      calculated_width = calculate_width(artworks, height)
    end
    height - 1
  end
end