Module: Fontisan::Ufo::Compile::Cpal

Defined in:
lib/fontisan/ufo/compile/cpal.rb

Overview

Builds the OpenType CPAL (Color Palette) table.

CPAL stores one or more palettes of BGRA color records, referenced by COLR layers and other color-glyph mechanisms.

See Also:

Defined Under Namespace

Classes: Color

Constant Summary collapse

VERSION = 
0
HEADER_SIZE = 
12
COLOR_RECORD_SIZE =

BGRA

4

Class Method Summary collapse

Class Method Details

.build(palettes:) ⇒ String?

Returns CPAL table bytes, or nil if no palettes.

Parameters:

  • palettes (Array<Array<Color>>) —

    one or more palettes, each an array of Color values. All palettes must have the same number of entries.

Returns:

  • (String, nil) —

    CPAL table bytes, or nil if no palettes



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# File 'lib/fontisan/ufo/compile/cpal.rb', line 28

def self.build(palettes:)
  return nil if palettes.nil? || palettes.empty?

  num_entries = palettes.first.size
  num_palettes = palettes.size
  num_records = num_entries * num_palettes

  indices = Array.new(num_palettes) { |i| i * num_entries }
  records = palettes.flatten

  offset = HEADER_SIZE + (num_palettes * 2) # header + indices

  io = +""
  io << [VERSION, num_entries, num_palettes, num_records, offset].pack("nnnnN")
  indices.each { |idx| io << [idx].pack("n") }
  records.each { |c| io << color_bytes(c) }
  io
end