Module: Kward::PixelLogo

Defined in:
lib/kward/resources/pixel_logo.rb

Overview

Pixel-art logo data and rendering helpers.

Constant Summary collapse

PNG_SIGNATURE = 
"\x89PNG\r\n\x1a\n".b.freeze
TRANSPARENT_ALPHA = 
128

Class Method Summary collapse

Class Method Details

.background_sgr(color) ⇒ Object 



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# File 'lib/kward/resources/pixel_logo.rb', line 224

def background_sgr(color)
  color ? "\e[48;2;#{color.join(";")}m" : "\e[49m"
end

.dominant_color(pixels, x_range, y_range) ⇒ Object 



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# File 'lib/kward/resources/pixel_logo.rb', line 149

def dominant_color(pixels, x_range, y_range)
  counts = Hash.new(0)
  y_range.each do |y|
    x_range.each do |x|
      counts[visible_color(pixels[y][x])] += 1
    end
  end
  counts.max_by { |_color, count| count }&.first
end

.each_chunk(data) ⇒ Object 



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# File 'lib/kward/resources/pixel_logo.rb', line 76

def each_chunk(data)
  offset = PNG_SIGNATURE.bytesize
  while offset < data.bytesize
    length = data[offset, 4].unpack1("N")
    type = data[offset + 4, 4]
    chunk = data[offset + 8, length]
    yield type, chunk
    offset += length + 12
  end
end

.foreground_sgr(color) ⇒ Object 



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# File 'lib/kward/resources/pixel_logo.rb', line 220

def foreground_sgr(color)
  color ? "\e[38;2;#{color.join(";")}m" : "\e[39m"
end

.half_block_cell(top, bottom) ⇒ Object 



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# File 'lib/kward/resources/pixel_logo.rb', line 208

def half_block_cell(top, bottom)
  if top && bottom
    [top, bottom, "▀"]
  elsif top
    [top, nil, "▀"]
  elsif bottom
    [bottom, nil, "▄"]
  else
    [nil, nil, " "]
  end
end

.half_block_rows_from_pixels(pixels, width:, pixel_height:) ⇒ Object 



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# File 'lib/kward/resources/pixel_logo.rb', line 31

def half_block_rows_from_pixels(pixels, width:, pixel_height:)
  scaled = scale_pixels(pixels, width: width, height: pixel_height)
  render_half_block_rows(scaled)
rescue StandardError
  []
end

.half_block_rows_from_png(path, width:, pixel_height:) ⇒ Object 



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# File 'lib/kward/resources/pixel_logo.rb', line 25

def half_block_rows_from_png(path, width:, pixel_height:)
  half_block_rows_from_pixels(indexed_png_pixels(path), width: width, pixel_height: pixel_height)
rescue StandardError
  []
end

.indexed_png_pixels(path) ⇒ Object 



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# File 'lib/kward/resources/pixel_logo.rb', line 38

def indexed_png_pixels(path)
  data = File.binread(path)
  raise "Invalid PNG" unless data.start_with?(PNG_SIGNATURE)

  png_width = nil
  png_height = nil
  bit_depth = nil
  color_type = nil
  interlace = nil
  palette = nil
  transparency = []
  idat = +"".b

  each_chunk(data) do |type, chunk|
    case type
    when "IHDR"
      png_width, png_height, bit_depth, color_type, _compression, _filter, interlace = chunk.unpack("NNCCCCC")
    when "PLTE"
      palette = chunk.bytes.each_slice(3).map { |red, green, blue| [red, green, blue, 255] }
    when "tRNS"
      transparency = chunk.bytes
    when "IDAT"
      idat << chunk
    end
  end

  raise "Unsupported PNG" unless png_width && png_height && palette
  raise "Unsupported PNG" unless bit_depth == 8 && color_type == 3 && interlace == 0

  transparency.each_with_index do |alpha, index|
    palette[index] = palette[index][0, 3] + [alpha] if palette[index]
  end

  unfilter_indexed_rows(Zlib::Inflate.inflate(idat), png_width, png_height).map do |row|
    row.map { |index| palette[index] || [0, 0, 0, 0] }
  end
end

.paeth(left, up, up_left) ⇒ Object 



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# File 'lib/kward/resources/pixel_logo.rb', line 123

def paeth(left, up, up_left)
  estimate = left + up - up_left
  left_distance = (estimate - left).abs
  up_distance = (estimate - up).abs
  up_left_distance = (estimate - up_left).abs
  return left if left_distance <= up_distance && left_distance <= up_left_distance
  return up if up_distance <= up_left_distance

  up_left
end

.render_half_block_rows(rows) ⇒ Object 



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# File 'lib/kward/resources/pixel_logo.rb', line 184

def render_half_block_rows(rows)
  rows.each_slice(2).map do |top_row, bottom_row|
    bottom_row ||= Array.new(top_row.length)
    current_foreground = nil
    current_background = nil
    rendered = +""
    top_row.each_with_index do |top, index|
      bottom = bottom_row[index]
      foreground, background, glyph = half_block_cell(top, bottom)
      if background != current_background
        rendered << background_sgr(background)
        current_background = background
      end
      if foreground != current_foreground
        rendered << foreground_sgr(foreground)
        current_foreground = foreground
      end
      rendered << glyph
    end
    rendered << reset_sgr if current_foreground || current_background
    rendered
  end
end

.render_rows(rows) ⇒ Object 



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# File 'lib/kward/resources/pixel_logo.rb', line 168

def render_rows(rows)
  rows.map do |row|
    current = nil
    rendered = +""
    row.each do |color|
      if color != current
        rendered << background_sgr(color)
        current = color
      end
      rendered << " "
    end
    rendered << reset_sgr if current
    rendered
  end
end

.reset_sgr ⇒ Object 



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# File 'lib/kward/resources/pixel_logo.rb', line 228

def reset_sgr
  "\e[0m"
end

.rows_from_pixels(pixels, width:, height:) ⇒ Object 



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# File 'lib/kward/resources/pixel_logo.rb', line 18

def rows_from_pixels(pixels, width:, height:)
  scaled = scale_pixels(pixels, width: width, height: height)
  render_rows(scaled)
rescue StandardError
  []
end

.rows_from_png(path, width:, height:) ⇒ Object 



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# File 'lib/kward/resources/pixel_logo.rb', line 12

def rows_from_png(path, width:, height:)
  rows_from_pixels(indexed_png_pixels(path), width: width, height: height)
rescue StandardError
  []
end

.scale_pixels(pixels, width:, height:) ⇒ Object 



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# File 'lib/kward/resources/pixel_logo.rb', line 134

def scale_pixels(pixels, width:, height:)
  source_height = pixels.length
  source_width = pixels.first.length

  height.times.map do |target_y|
    source_y_start = target_y * source_height / height
    source_y_end = [(target_y + 1) * source_height / height, source_y_start + 1].max
    width.times.map do |target_x|
      source_x_start = target_x * source_width / width
      source_x_end = [(target_x + 1) * source_width / width, source_x_start + 1].max
      dominant_color(pixels, source_x_start...source_x_end, source_y_start...source_y_end)
    end
  end
end

.unfilter_indexed_rows(raw, width, height) ⇒ Object 



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# File 'lib/kward/resources/pixel_logo.rb', line 87

def unfilter_indexed_rows(raw, width, height)
  rows = []
  previous = Array.new(width, 0)
  offset = 0

  height.times do
    filter = raw.getbyte(offset)
    offset += 1
    scanline = raw.byteslice(offset, width).bytes
    offset += width
    row = unfilter_scanline(scanline, previous, filter)
    rows << row
    previous = row
  end

  rows
end

.unfilter_scanline(scanline, previous, filter) ⇒ Object 



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# File 'lib/kward/resources/pixel_logo.rb', line 105

def unfilter_scanline(scanline, previous, filter)
  row = []
  scanline.each_with_index do |byte, index|
    left = index.zero? ? 0 : row[index - 1]
    up = previous[index] || 0
    up_left = index.zero? ? 0 : previous[index - 1]
    row << case filter
           when 0 then byte
           when 1 then (byte + left) & 0xff
           when 2 then (byte + up) & 0xff
           when 3 then (byte + ((left + up) / 2)) & 0xff
           when 4 then (byte + paeth(left, up, up_left)) & 0xff
           else byte
           end
  end
  row
end

.visible_color(color) ⇒ Object 



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# File 'lib/kward/resources/pixel_logo.rb', line 159

def visible_color(color)
  return nil unless color

  red, green, blue, alpha = color
  return nil if !alpha.nil? && alpha.to_i < TRANSPARENT_ALPHA

  [red, green, blue]
end