Class: Echoes::SixelDecoder

Inherits:
Object
  • Object
show all
Defined in:
lib/echoes/sixel_decoder.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(params = []) ⇒ SixelDecoder

Returns a new instance of SixelDecoder.



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# File 'lib/echoes/sixel_decoder.rb', line 7

def initialize(params = [])
  @background_mode = params[1] || 0
  @color_registers = default_color_registers
  @current_color = 0
  @cursor_x = 0
  @cursor_y = 0
  @width = 0
  @height = 0
  @pixels = {}
  @declared_width = 0
  @declared_height = 0
end

Instance Attribute Details

#height ⇒ Object (readonly)

Returns the value of attribute height.



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# File 'lib/echoes/sixel_decoder.rb', line 5

def height
  @height
end

#width ⇒ Object (readonly)

Returns the value of attribute width.



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# File 'lib/echoes/sixel_decoder.rb', line 5

def width
  @width
end

Instance Method Details

#decode(data) ⇒ Object 



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# File 'lib/echoes/sixel_decoder.rb', line 20

def decode(data)
  i = 0
  len = data.bytesize

  while i < len
    byte = data.getbyte(i)

    case byte
    when 0x21 # '!' repeat
      i, count, ch = parse_repeat(data, i + 1)
      paint_sixel(ch, count) if ch
    when 0x22 # '"' raster attributes
      i, _, _, ph, pv = parse_raster_attributes(data, i + 1)
      @declared_width = ph if ph > 0
      @declared_height = pv if pv > 0
    when 0x23 # '#' color
      i = parse_color(data, i + 1)
    when 0x24 # '$' graphics CR
      @cursor_x = 0
      i += 1
    when 0x2D # '-' graphics newline
      @cursor_x = 0
      @cursor_y += 6
      i += 1
    when 0x3F..0x7E # sixel character
      paint_sixel(byte, 1)
      i += 1
    else
      i += 1
    end
  end

  @width = @declared_width if @declared_width > @width
  @height = @declared_height if @declared_height > @height
  self
end

#to_rgba ⇒ Object 



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# File 'lib/echoes/sixel_decoder.rb', line 57

def to_rgba
  buf = "\x00".b * (@width * @height * 4)
  transparent = @background_mode == 1

  @pixels.each do |(x, y), color|
    next if x >= @width || y >= @height

    offset = (y * @width + x) * 4
    buf.setbyte(offset,     color[0])
    buf.setbyte(offset + 1, color[1])
    buf.setbyte(offset + 2, color[2])
    buf.setbyte(offset + 3, 255)
  end

  unless transparent
    # Set alpha=255 for unset pixels (background fill)
    (@width * @height).times do |i|
      offset = i * 4
      buf.setbyte(offset + 3, 255) if buf.getbyte(offset + 3) == 0
    end
  end

  buf
end