Class: Pura::Ico::Encoder

Inherits:
Object
  • Object
show all
Defined in:
lib/pura/ico/encoder.rb

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(images) ⇒ Encoder

Returns a new instance of Encoder.



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# File 'lib/pura/ico/encoder.rb', line 14

def initialize(images)
  @images = images
end

Class Method Details

.encode(images, output_path) ⇒ Object 



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# File 'lib/pura/ico/encoder.rb', line 6

def self.encode(images, output_path)
  images = [images] unless images.is_a?(Array)
  encoder = new(images)
  data = encoder.encode
  File.binwrite(output_path, data)
  data.bytesize
end

Instance Method Details

#encode ⇒ Object 



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# File 'lib/pura/ico/encoder.rb', line 18

def encode
  require "pura-png"

  count = @images.size

  # Encode each image as PNG data
  png_blobs = @images.map { |img| encode_png_blob(img) }

  # Calculate offsets
  # Header: 6 bytes
  # Directory entries: 16 bytes each
  header_size = 6 + (16 * count)
  offsets = []
  current_offset = header_size
  png_blobs.each do |blob|
    offsets << current_offset
    current_offset += blob.bytesize
  end

  out = String.new(encoding: Encoding::BINARY, capacity: current_offset)

  # ICO header
  out << [0, 1, count].pack("v3") # reserved=0, type=1 (ICO), count

  # Directory entries
  @images.each_with_index do |img, i|
    w = img.width >= 256 ? 0 : img.width
    h = img.height >= 256 ? 0 : img.height

    out << [
      w,           # width (0 = 256)
      h,           # height (0 = 256)
      0,           # color count (0 for >= 256 colors)
      0,           # reserved
      1,           # color planes
      32 # bits per pixel
    ].pack("C4v2")
    out << [
      png_blobs[i].bytesize,  # data size
      offsets[i]              # data offset
    ].pack("V2")
  end

  # Image data (PNG blobs)
  png_blobs.each { |blob| out << blob }

  out
end