Class: RubySpriter::BackgroundSampler

Inherits:
Object
  • Object
show all
Defined in:
lib/ruby_spriter/background_sampler.rb

Overview

BackgroundSampler collects unique background colors from interior image regions

Sampling Strategy:

  • Starts at (sample_offset, sample_offset) to avoid edge compression artifacts

  • Samples horizontally across the image with calculated intervals

  • Moves to next row if not enough unique colors found

  • Uses pixel cache for fast lookups (loads all pixels once)

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(image_path, sample_offset = 5, sample_count = 10, max_rows = 20) ⇒ BackgroundSampler

Returns a new instance of BackgroundSampler.



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# File 'lib/ruby_spriter/background_sampler.rb', line 16

def initialize(image_path, sample_offset = 5, sample_count = 10, max_rows = 20)
  @image_path = image_path
  @sample_offset = sample_offset
  @sample_count = sample_count
  @max_rows = max_rows
  @image_width = nil
  @image_height = nil
  @pixel_cache = nil
end

Instance Attribute Details

#image_path ⇒ Object (readonly)

Returns the value of attribute image_path.



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# File 'lib/ruby_spriter/background_sampler.rb', line 14

def image_path
  @image_path
end

#max_rows ⇒ Object (readonly)

Returns the value of attribute max_rows.



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# File 'lib/ruby_spriter/background_sampler.rb', line 14

def max_rows
  @max_rows
end

#sample_count ⇒ Object (readonly)

Returns the value of attribute sample_count.



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# File 'lib/ruby_spriter/background_sampler.rb', line 14

def sample_count
  @sample_count
end

#sample_offset ⇒ Object (readonly)

Returns the value of attribute sample_offset.



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# File 'lib/ruby_spriter/background_sampler.rb', line 14

def sample_offset
  @sample_offset
end

Instance Method Details

#collect_unique_colors ⇒ Object

Collect unique background colors by sampling interior regions



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# File 'lib/ruby_spriter/background_sampler.rb', line 27

def collect_unique_colors
  load_image_dimensions
  load_pixel_cache

  # Input validation

  if @sample_count < 2
    raise ValidationError, "sample_count must be at least 2"
  end

  usable_width = @image_width - (2 * @sample_offset)
  if usable_width <= 0
    raise ValidationError, "sample_offset (#{@sample_offset}) too large for image width (#{@image_width})"
  end

  unique_colors = []
  y = @sample_offset
  rows_sampled = 0

  while unique_colors.length < @sample_count && rows_sampled < @max_rows
    # Calculate interval across usable width (excluding offset margins on both sides)

    interval = (@image_width - 2 * @sample_offset).to_f / (@sample_count - 1)

    # Sample across the width at current y position

    @sample_count.times do |i|
      x = @sample_offset + (i * interval).round

      # Ensure x is within bounds

      x = x.clamp(@sample_offset, @image_width - @sample_offset - 1)

      color = sample_pixel(x, y)

      if color && !color_exists?(unique_colors, color)
        unique_colors << color
        break if unique_colors.length >= @sample_count
      end
    end

    # Move to next row

    y += 1
    rows_sampled += 1
  end

  unique_colors
end