imageblur.rb

class Image
  attr_accessor :array

  def initialize(array)
    @array = array
    @cells = []
    @new_array = @array.map {|e| Array.new(e.size) }
  end

  def all_array_indexes 

    #Returns all possible array indexes within the size of the array
    
    column_index = @array.first.size - 1
    row_index = @array.size - 1
    
    (0..row_index).to_a.product((0..column_index).to_a)

  end

  def manhattan_cells(x,y,n)
    
    #Selects only cells within a manhattan distance of n relevant to a specified point 
    #Stores all cells into instance variable @cells

    @cells = all_array_indexes.select { |i,j| ( (x-i).abs ) + ( (y-j).abs ) <= n }

  end

  def update_cells

    #Goes through each value in @cells and plugs the row index (a) and column index (b) in @new_array[a][b]

    @cells.uniq.each do |a,b|
      @new_array[a][b] = 1
    end
  end

  def output_image
    @array.each do |i|
      puts i.join("")
    end
  end

  def blur(n)

    #Where it all comes together

    @array.each_with_index do |row,x| 
      row.each_with_index do |cell,y|      
        if @array[x][y] == 1 
          manhattan_cells(x,y,n)
          update_cells
        else
          @new_array[x][y] ||= @array[x][y] 

          #Sets value to 0 in @new_array since it was also 0 in @array

        end 
      end
    end 
    
  return Image.new(@new_array).output_image
  
  end

end

image = Image.new([
          [0, 0, 0, 0, 0, 0, 0, 0, 1],
          [0, 0, 0, 0, 0, 0, 0, 0, 0],
          [0, 0, 0, 0, 0, 0, 0, 0, 0],
          [0, 0, 0, 0, 0, 0, 0, 0, 0],
          [0, 0, 0, 0, 0, 0, 0, 0, 0],
          [0, 0, 0, 0, 1, 0, 0, 0, 0],
          [0, 0, 0, 0, 0, 0, 0, 0, 0],
          [0, 0, 0, 0, 0, 0, 0, 0, 0],
          [0, 0, 0, 0, 0, 0, 0, 0, 0],
          [0, 0, 0, 0, 0, 0, 0, 0, 0],
          [0, 0, 0, 0, 0, 0, 0, 0, 0],
          [0, 0, 0, 0, 0, 0, 0, 0, 1],
        ])

image.blur(4)

imageblur2_spec.rb

require 'rspec'
require_relative 'imageblur'

describe Image do
  describe '#blur' do
    context 'with a 5 by 5 array and n of 2' do
      it 'moves a manhattan distance of 2' do
        image = Image.new([
          [0, 0, 0, 0, 0],
          [0, 0, 0, 0, 0],
          [0, 0, 1, 0, 0],
          [0, 0, 0, 0, 0],
          [0, 0, 0, 0, 0]
        ])

        new_image = Image.new([
          [0, 0, 1, 0, 0],
          [0, 1, 1, 1, 0],
          [1, 1, 1, 1, 1],
          [0, 1, 1, 1, 0],
          [0, 0, 1, 0, 0]
        ])

        expect(image.blur(2)).to eql(new_image.output_image)
      end
    end

    context 'with a 9 by 12 array and n of 3' do
      it 'moves a manhattan distance of 3' do
        image = Image.new([
          [0, 0, 0, 0, 0, 0, 0, 0, 0],
          [0, 0, 0, 0, 0, 0, 0, 0, 0],
          [0, 0, 0, 0, 0, 0, 0, 0, 0],
          [0, 0, 0, 0, 0, 0, 0, 0, 0],
          [0, 0, 0, 0, 0, 0, 0, 0, 0],
          [0, 0, 0, 0, 1, 0, 0, 0, 0],
          [0, 0, 0, 0, 0, 0, 0, 0, 0],
          [0, 0, 0, 0, 0, 0, 0, 0, 0],
          [0, 0, 0, 0, 0, 0, 0, 0, 0],
          [0, 0, 0, 0, 0, 0, 0, 0, 0],
          [0, 0, 0, 0, 0, 0, 0, 0, 0],
          [0, 0, 0, 0, 0, 0, 0, 0, 1],
        ])

        new_image = Image.new([
          [0, 0, 0, 0, 0, 0, 0, 0, 0],
          [0, 0, 0, 0, 0, 0, 0, 0, 0],
          [0, 0, 0, 0, 1, 0, 0, 0, 0],
          [0, 0, 0, 1, 1, 1, 0, 0, 0],
          [0, 0, 1, 1, 1, 1, 1, 0, 0],
          [0, 1, 1, 1, 1, 1, 1, 1, 0],
          [0, 0, 1, 1, 1, 1, 1, 0, 0],
          [0, 0, 0, 1, 1, 1, 0, 0, 0],
          [0, 0, 0, 0, 1, 0, 0, 0, 1],
          [0, 0, 0, 0, 0, 0, 0, 1, 1],
          [0, 0, 0, 0, 0, 0, 1, 1, 1],
          [0, 0, 0, 0, 0, 1, 1, 1, 1],
        ])

        expect(image.blur(3)).to eql(new_image.output_image)
      end
    end    
      
    describe '#all array indexes' do
      it 'returns all possible array indexes based on size of array' do
        image = Image.new([
          [0, 0, 0, 0, 0],
          [0, 0, 0, 0, 0],
          [0, 0, 1, 0, 0],
          [0, 0, 0, 0, 0],
          [0, 0, 0, 0, 0]
        ])

        result = [
        [0, 0], [0, 1], [0, 2], [0, 3], 
        [0, 4], [1, 0], [1, 1], [1, 2], 
        [1, 3], [1, 4], [2, 0], [2, 1], 
        [2, 2], [2, 3], [2, 4], [3, 0], 
        [3, 1], [3, 2], [3, 3], [3, 4], 
        [4, 0], [4, 1], [4, 2], [4, 3], 
        [4, 4]
        ]

        expect(image.all_array_indexes).to eql(result)
      end

      context 'when array is 12 by 9' do
        it 'returns all possible array indexes in a 12 by 9 array' do
        
          image = Image.new([
            [0, 0, 0, 0, 0, 0, 0, 0, 0],
            [0, 0, 0, 0, 0, 0, 0, 0, 0],
            [0, 0, 0, 0, 0, 0, 0, 0, 0],
            [0, 0, 0, 0, 0, 0, 0, 0, 0],
            [0, 0, 0, 0, 0, 0, 0, 0, 0],
            [0, 0, 0, 0, 0, 0, 0, 0, 0],
            [0, 0, 0, 0, 0, 0, 0, 0, 0],
            [0, 0, 0, 0, 0, 0, 0, 0, 0],
            [0, 0, 0, 0, 0, 0, 0, 0, 0],
            [0, 0, 0, 0, 0, 0, 0, 0, 0],
            [0, 0, 0, 0, 0, 0, 0, 0, 0],
            [0, 0, 0, 0, 0, 0, 0, 0, 0],
          ])

          result = [
          [0, 0], [0, 1], [0, 2], [0, 3], 
          [0, 4], [0, 5], [0, 6], [0, 7], 
          [0, 8], [1, 0], [1, 1], [1, 2], [1, 3], 
          [1, 4], [1, 5], [1, 6], [1, 7], [1, 8], 
          [2, 0], [2, 1], [2, 2], [2, 3], [2, 4], 
          [2, 5], [2, 6], [2, 7], [2, 8], [3, 0], 
          [3, 1], [3, 2], [3, 3], [3, 4], [3, 5], 
          [3, 6], [3, 7], [3, 8], [4, 0], [4, 1], 
          [4, 2], [4, 3], [4, 4], [4, 5], [4, 6], 
          [4, 7], [4, 8], [5, 0], [5, 1], [5, 2], 
          [5, 3], [5, 4], [5, 5], [5, 6], [5, 7], 
          [5, 8], [6, 0], [6, 1], [6, 2], [6, 3], 
          [6, 4], [6, 5], [6, 6], [6, 7], [6, 8], 
          [7, 0], [7, 1], [7, 2], [7, 3], [7, 4], 
          [7, 5], [7, 6], [7, 7], [7, 8], [8, 0], 
          [8, 1], [8, 2], [8, 3], [8, 4], [8, 5], 
          [8, 6], [8, 7], [8, 8], [9, 0], [9, 1], 
          [9, 2], [9, 3], [9, 4], [9, 5], [9, 6], 
          [9, 7], [9, 8], [10, 0], [10, 1], [10, 2], 
          [10, 3], [10, 4], [10, 5], [10, 6], [10, 7],
          [10, 8], [11, 0], [11, 1], [11, 2], [11, 3], 
          [11, 4], [11, 5], [11, 6], [11, 7], [11, 8]
        ]

        expect(image.all_array_indexes).to eql(result)
        
        end
      end

    end

    describe '#manhattan cells' do
      it 'selects and returns only cells within n manhattan distance' do
        image = Image.new([
          [0, 0, 0, 0, 0],
          [0, 0, 0, 0, 0],
          [0, 0, 1, 0, 0],
          [0, 0, 0, 0, 0],
          [0, 0, 0, 0, 0]
        ])


        cells = [
        [0, 2], [1, 1], [1, 2], [1, 3], 
        [2, 0], [2, 1], [2, 2], [2, 3], 
        [2, 4], [3, 1], [3, 2], [3, 3], 
        [4, 2] 
        ]

        expect(image.manhattan_cells(2,2,2)).to eql(cells)
      end

      context 'when pixel is in a corner' do
        it 'return only cells in the dimensions of the array' do
          image = Image.new([
          [0, 0, 0, 0, 0, 0, 0, 0, 0],
          [0, 0, 0, 0, 0, 0, 0, 0, 0],
          [0, 0, 0, 0, 0, 0, 0, 0, 0],
          [0, 0, 0, 0, 0, 0, 0, 0, 0],
          [0, 0, 0, 0, 0, 0, 0, 0, 0],
          [0, 0, 0, 0, 0, 0, 0, 0, 0],
          [0, 0, 0, 0, 0, 0, 0, 0, 0],
          [0, 0, 0, 0, 0, 0, 0, 0, 0],
          [0, 0, 0, 0, 0, 0, 0, 0, 0],
          [0, 0, 0, 0, 0, 0, 0, 0, 0],
          [0, 0, 0, 0, 0, 0, 0, 0, 0],
          [0, 0, 0, 0, 0, 0, 0, 0, 1],
        ])


          cells = [
          [9,8],[10,7],[10,8],[11,6],[11,7],[11,8]
          ]

          expect(image.manhattan_cells(11,8,2)).to eql(cells)
        end
      end
    end

  end
end

Great work! congrats!