Module: ChunkyPNG::Canvas::Adam7Interlacing
- Included in:
- ChunkyPNG::Canvas
- Defined in:
- lib/chunky_png/canvas/adam7_interlacing.rb
Overview
Methods for decoding and encoding adam7 interlacing
Instance Method Summary collapse
- #adam7_extract_pass(pass, canvas) ⇒ Object
- #adam7_merge_pass(pass, canvas, subcanvas) ⇒ Object
- #adam7_multiplier_offset(pass) ⇒ Object
- #adam7_pass_size(pass, original_width, original_height) ⇒ Object
- #adam7_pass_sizes(original_width, original_height) ⇒ Object
Instance Method Details
#adam7_extract_pass(pass, canvas) ⇒ Object
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# File 'lib/chunky_png/canvas/adam7_interlacing.rb', line 39 def adam7_extract_pass(pass, canvas) m_o = adam7_multiplier_offset(pass) sm_pixels = [] m_o[:y_offset].step(canvas.height - 1, m_o[:y_multiplier]) do |y| m_o[:x_offset].step(canvas.width - 1, m_o[:x_multiplier]) do |x| sm_pixels << canvas[x, y] end end new_canvas_args = adam7_pass_size(pass, canvas.width, canvas.height) + [sm_pixels] ChunkyPNG::Canvas.new(*new_canvas_args) end |
#adam7_merge_pass(pass, canvas, subcanvas) ⇒ Object
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# File 'lib/chunky_png/canvas/adam7_interlacing.rb', line 27 def adam7_merge_pass(pass, canvas, subcanvas) m_o = adam7_multiplier_offset(pass) 0.upto(subcanvas.height - 1) do |y| 0.upto(subcanvas.width - 1) do |x| new_x = x * m_o[:x_multiplier] + m_o[:x_offset] new_y = y * m_o[:y_multiplier] + m_o[:y_offset] canvas[new_x, new_y] = subcanvas[x, y] end end canvas end |
#adam7_multiplier_offset(pass) ⇒ Object
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# File 'lib/chunky_png/canvas/adam7_interlacing.rb', line 8 def adam7_multiplier_offset(pass) { :x_multiplier => 8 >> (pass >> 1), :x_offset => (pass & 1 == 0) ? 0 : 8 >> ((pass + 1) >> 1), :y_multiplier => pass == 0 ? 8 : 8 >> ((pass - 1) >> 1), :y_offset => (pass == 0 || pass & 1 == 1) ? 0 : 8 >> (pass >> 1) } end |
#adam7_pass_size(pass, original_width, original_height) ⇒ Object
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# File 'lib/chunky_png/canvas/adam7_interlacing.rb', line 17 def adam7_pass_size(pass, original_width, original_height) m_o = adam7_multiplier_offset(pass) [ ((original_width - m_o[:x_offset] ) / m_o[:x_multiplier].to_f).ceil, ((original_height - m_o[:y_offset] ) / m_o[:y_multiplier].to_f).ceil] end |
#adam7_pass_sizes(original_width, original_height) ⇒ Object
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# File 'lib/chunky_png/canvas/adam7_interlacing.rb', line 23 def adam7_pass_sizes(original_width, original_height) (0...7).map { |pass| adam7_pass_size(pass, original_width, original_height) } end |