Class: Aspera::Preview::Terminal

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

Overview

Render an image for terminal output. Uses either colored text blocks or the iTerm2 inline-image protocol when available.

Class Method Summary collapse

Class Method Details

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

Render an image blob for display in the current terminal.

Parameters:

  • blob (String) —

    The image as a binary string

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

    ‘true` to display the image as text, `false` to use iTerm2 if supported

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

    Number of lines to reserve for other text than the image

  • 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 130

def build(blob, text: false, reserve: 3, double: true, font_ratio: DEFAULT_FONT_RATIO)
  return '[Image display requires a terminal]' unless Environment.terminal?
  return iterm_display_image(blob) if iterm_supported? && !text
  pixel_colors =
    begin
      Log.log.debug('Trying chunky_png')
      Backend::ChunkyPNG.new(blob, reserve: reserve, double: double, font_ratio: font_ratio).terminal_pixels
    rescue => e
      Log.log.debug(e.message)
      begin
        Log.log.debug('Trying rmagick')
        Backend::RMagick.new(blob, reserve: reserve, double: double, font_ratio: font_ratio).terminal_pixels
      rescue => e
        Log.log.debug(e.message)
        nil
      end
    end
  if pixel_colors.nil?
    return iterm_display_image(blob) if iterm_supported?
    raise 'Cannot decode picture.'
  end
  # Convert decoded pixels into terminal glyphs.
  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) ⇒ String

Build the iTerm2 inline-image escape sequence. iterm2.com/documentation-images.html

Parameters:

  • blob (String) —

    image binary content

Returns:

  • (String) —

    escape sequence that displays the image inline



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# File 'lib/aspera/preview/terminal.rb', line 172

def iterm_display_image(blob)
  # image = Magick::ImageList.new.from_blob(blob)
  # Parameters accepted by the iTerm2 inline-image protocol.
  arguments = {
    inline:              1,
    preserveAspectRatio: 1,
    size:                blob.length
    # width:               image.columns,
    # height:              image.rows
  }.map{ |k, v| "#{k}=#{v}"}.join(';')
  # `\a` is BEL and `\e` is ESC.
  # See: https://github.com/ruby/ruby/blob/master/doc/syntax/literals.rdoc#label-Strings
  # Return the full escape sequence expected by iTerm2-compatible terminals.
  return "\e]1337;File=#{arguments}:#{Base64.strict_encode64(blob)}\a"
end

.iterm_supported? ⇒ Boolean

Detect whether the current terminal supports iTerm2 inline images.

Returns:

  • (Boolean) —

    ‘true` when the current terminal advertises iTerm2 image support



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# File 'lib/aspera/preview/terminal.rb', line 191

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