Class: Btape::Palette::Adaptive

Inherits:
Object
  • Object
show all
Defined in:
lib/btape/palette.rb

Overview

Colours chosen from the frames themselves by median cut.

Constant Summary collapse

MAX_SAMPLES_PER_IMAGE =

Enough of each frame to describe what colours it uses. Reading every pixel of every frame would cost far more and change the answer very little.

60_000

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(histogram) ⇒ Adaptive

Returns a new instance of Adaptive.



86
87
88
89
90
91
92
 
# File 'lib/btape/palette.rb', line 86

def initialize(histogram)
  @colours = MedianCut.new(histogram).colours
  # One entry per five-bit colour cell, filled in as cells are met. A
  # screenshot touches a small fraction of them, so searching the
  # palette for the rest would be work thrown away.
  @lookup = Array.new(CELLS)
end

Instance Attribute Details

#colours ⇒ Object (readonly)

Returns the value of attribute colours.



94
95
96
 
# File 'lib/btape/palette.rb', line 94

def colours
  @colours
end

Class Method Details

.from(images) ⇒ Object 



68
69
70
 
# File 'lib/btape/palette.rb', line 68

def self.from(images)
  new(histogram(images))
end

.histogram(images) ⇒ Object 



72
73
74
75
76
77
78
79
80
81
82
83
84
 
# File 'lib/btape/palette.rb', line 72

def self.histogram(images)
  counts = Hash.new(0)
  images.each do |image|
    pixels = image.pixels
    stride = [pixels.length / MAX_SAMPLES_PER_IMAGE, 1].max
    index = 0
    while index < pixels.length
      counts[Palette.cell(pixels[index])] += 1
      index += stride
    end
  end
  counts
end

Instance Method Details

#index_for(pixel) ⇒ Object 



96
97
98
99
 
# File 'lib/btape/palette.rb', line 96

def index_for(pixel)
  cell = Palette.cell(pixel)
  @lookup[cell] || (@lookup[cell] = nearest(cell))
end

#to_gct ⇒ Object 



101
102
103
 
# File 'lib/btape/palette.rb', line 101

def to_gct
  Palette.colour_table(@colours)
end