Class: Theseus::Mask

Inherits:
Object
  • Object
show all
Defined in:
lib/theseus/mask.rb

Overview

A “mask” is, conceptually, a grid of true/false values that corresponds, one-to-one, with the cells of a maze object. For every mask cell that is true, the corresponding cell in a maze may contain passages. For every mask cell that is false, the corresponding maze cell must be blank.

Any object may be used as a mask as long as it responds to #height, #width, and #[].

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(grid) ⇒ Mask

Instantiate a new mask from the given grid, which must be an Array of rows, and each row must be an Array of true/false values for each column in the row.



54
55
56
57
58
 
# File 'lib/theseus/mask.rb', line 54

def initialize(grid)
  @grid = grid
  @height = @grid.length
  @width = @grid.map { |row| row.length }.max
end

Instance Attribute Details

#height ⇒ Object (readonly)

The number of rows in the mask.



47
48
49
 
# File 'lib/theseus/mask.rb', line 47

def height
  @height
end

#width ⇒ Object (readonly)

the length of the longest row in the mask.



50
51
52
 
# File 'lib/theseus/mask.rb', line 50

def width
  @width
end

Class Method Details

.from_png(file_name) ⇒ Object

Given a PNG file with the given file_name, read the file and create a new mask where transparent pixels will be considered true, and all others false. Note that a pixel with any transparency at all will be considered true.

The resulting mask will have the same dimensions as the image file.



40
41
42
43
44
 
# File 'lib/theseus/mask.rb', line 40

def self.from_png(file_name)
  image = ChunkyPNG::Image.from_file(file_name)
  grid = Array.new(image.height) { |y| Array.new(image.width) { |x| (image[x, y] & 0xff) == 0 } }
  new(grid)
end

.from_text(text) ⇒ Object

Given a string, treat each line as rows and each character as a cell. Every period character (“.”) will be mapped to true, and everything else to false. This lets you define simple masks as ASCII art:

mask_string = "..........\n.X....XXX.\n..X....XX.\n...X....X.\n....X.....\n.....X....\n.X....X...\n.XX....X..\n.XXX....X.\n..........\n"

mask = Theseus::Mask.from_text(mask_string)



31
32
33
 
# File 'lib/theseus/mask.rb', line 31

def self.from_text(text)
  new(text.strip.split(/\n/).map { |line| line.split(//).map { |c| c == '.' } })
end

Instance Method Details

#[](x, y) ⇒ Object

Returns the true/false value for the corresponding cell in the grid.



61
62
63
 
# File 'lib/theseus/mask.rb', line 61

def [](x,y)
  @grid[y][x]
end