Class: Aspera::Preview::Terminal

Inherits:
Object
  • Object
show all
Defined in:
lib/aspera/preview/terminal.rb

Overview

Display a picture in the terminal, either using coloured characters or iTerm2

Class Method Summary collapse

Class Method Details

.build(blob, reserve: 3, text: false, double: true, font_ratio: DEFAULT_FONT_RATIO) ⇒ String

Returns the image as text, or the iTerm2 escape sequence.

Parameters:

  • blob (String) —

    the image as a binary string

  • reserve (Integer) (defaults to: 3) —

    number of lines to reserve for other text than the image

  • text (Boolean) (defaults to: false) —

    true to display the image as text, false to use iTerm2

  • double (Boolean) (defaults to: true) —

    true to use colors on half lines, false to use colors on full lines

  • font_ratio (Float) (defaults to: DEFAULT_FONT_RATIO) —

    ratio = font height / font width

Returns:

  • (String) —

    the image as text, or the iTerm2 escape sequence



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# File 'lib/aspera/preview/terminal.rb', line 28

def build(blob, reserve: 3, text: false, double: true, font_ratio: DEFAULT_FONT_RATIO)
  return iterm_display_image(blob) if iterm_supported? && !text
  begin
    # do not require statically, as the package is optional
    require 'rmagick' # https://rmagick.github.io/index.html
  rescue LoadError => e
    Log.log.error('Install missing gem: gem install rmagick')
    # fallback to iterm, if supported
    return iterm_display_image(blob) if iterm_supported?
    Log.log.error('Cant display picture.')
    raise e
  end
  image = Magick::ImageList.new.from_blob(blob)
  (term_rows, term_columns) = IO.console.winsize
  term_rows -= reserve
  # compute scaling to fit terminal
  fit_term_ratio = [term_rows.to_f * font_ratio / image.rows.to_f, term_columns.to_f / image.columns.to_f].min
  height_ratio = double ? 2.0 : 1.0
  image = image.scale((image.columns * fit_term_ratio).to_i, (image.rows * fit_term_ratio * height_ratio / font_ratio).to_i)
  # quantum depth is 8 or 16, see: `magick xc: -format "%q" info:`
  shift_for_8_bit = Magick::MAGICKCORE_QUANTUM_DEPTH - 8
  # get all pixel colors, adjusted for Rainbow
  pixel_colors = []
  image.each_pixel do |pixel, col, row|
    pixel_rgb = [pixel.red, pixel.green, pixel.blue]
    pixel_rgb = pixel_rgb.map { |color| color >> shift_for_8_bit } unless shift_for_8_bit.eql?(0)
    # init 2-dim array
    pixel_colors[row] ||= []
    pixel_colors[row][col] = pixel_rgb
  end
  # now generate text
  text_pixels = []
  pixel_colors.each_with_index do |row_data, row|
    next if double && (row.odd? || row.eql?(pixel_colors.length - 1))
    row_data.each_with_index do |pixel_rgb, col|
      text_pixels.push("\n") if col.eql?(0) && !row.eql?(0)
      if double
        text_pixels.push(Rainbow('▄').background(pixel_rgb).foreground(pixel_colors[row + 1][col]))
      else
        text_pixels.push(Rainbow(' ').background(pixel_rgb))
      end
    end
  end
  return text_pixels.join
end

.iterm_display_image(blob) ⇒ Object

display image in iTerm2 iterm2.com/documentation-images.html



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# File 'lib/aspera/preview/terminal.rb', line 76

def iterm_display_image(blob)
  # image = Magick::ImageList.new.from_blob(blob)
  # parameters for iTerm2 image display
  arguments = {
    inline:              1,
    preserveAspectRatio: 1,
    size:                blob.length
    # width:               image.columns,
    # height:              image.rows
  }.map { |k, v| "#{k}=#{v}" }.join(';')
  # \a is BEL, \e is ESC : https://github.com/ruby/ruby/blob/master/doc/syntax/literals.rdoc#label-Strings
  # escape sequence for iTerm2 image display
  return "\e]1337;File=#{arguments}:#{Base64.encode64(blob)}\a"
end

.iterm_supported? ⇒ Boolean

Returns true if the terminal supports iTerm2 image display.

Returns:

  • (Boolean) —

    true if the terminal supports iTerm2 image display



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# File 'lib/aspera/preview/terminal.rb', line 92

def iterm_supported?
  TERM_ENV_VARS.each do |env_var|
    return true if ITERM_NAMES.any? { |term| ENV[env_var]&.include?(term) }
  end
  false
end