Module: Okmain::DistanceMask

Defined in:
lib/okmain/distance_mask.rb

Constant Summary collapse

SATURATED_THRESHOLD = 
0.75

Class Method Summary collapse

Class Method Details

.compute(width, height) ⇒ Object

Returns a flat Array of mask values (0.1..1.0) for each pixel, matching Rust’s rectangular mask. Center pixels get 1.0, corner pixels get 0.1, with a linear ramp.



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# File 'lib/okmain/distance_mask.rb', line 11

def compute(width, height)
  half_w = width * 0.5
  half_h = height * 0.5
  x_threshold = half_w * SATURATED_THRESHOLD
  y_threshold = half_h * SATURATED_THRESHOLD

  mask = Array.new(width * height)
  y = 0
  while y < height
    # Distance from nearest y-edge (0 at edge, half_h at center)
    my = y < half_h ? y.to_f : (height - 1 - y).to_f
    y_contrib = if y_threshold > 0.0
                  v = 0.1 + 0.9 * (my / y_threshold)
                  v < 1.0 ? v : 1.0
                else
                  1.0
                end

    row_offset = y * width
    x = 0
    while x < width
      # Distance from nearest x-edge (0 at edge, half_w at center)
      mx = x < half_w ? x.to_f : (width - 1 - x).to_f
      x_contrib = if x_threshold > 0.0
                    v = 0.1 + 0.9 * (mx / x_threshold)
                    v < 1.0 ? v : 1.0
                  else
                    1.0
                  end

      mask[row_offset + x] = x_contrib < y_contrib ? x_contrib : y_contrib
      x += 1
    end
    y += 1
  end

  mask
end