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module Cairo
class Context
module Path
def transform_path(path, &block)
transformed_path = Cairo::Path.new
path.each do |type, points|
case type
when PATH_MOVE_TO
transformed_path.move_to(*points.collect(&block).flatten)
when PATH_LINE_TO
transformed_path.line_to(*points.collect(&block).flatten)
when PATH_CURVE_TO
transformed_path.curve_to(*points.collect(&block).flatten)
when PATH_CLOSE_PATH
transformed_path.close
end
end
transformed_path
end
def map_path_onto(path)
parameterized_path = parameterize_path(path)
transformed_path = transform_path(copy_path) do |x, y|
current_point = nil
d = x
i = -1
type = points = nil
path.each do |_type, _points|
type, points = _type, _points
i += 1
break if d < parameterized_path[i]
d -= parameterized_path[i]
case type
when PATH_MOVE_TO
current_point = points[0]
when PATH_LINE_TO
current_point = points[0]
when PATH_CURVE_TO
current_point = points[2]
when PATH_CLOSE_PATH
end
end
case type
when PATH_MOVE_TO
[x, y]
when PATH_LINE_TO
ratio = d / parameterized_path[i]
current_x, current_y = current_point
lx, ly = points[0]
new_x = current_x * (1 - ratio) + lx * ratio
new_y = current_y * (1 - ratio) + ly * ratio
dx = -(current_x - lx)
dy = -(current_y - ly)
ratio = y / parameterized_path[i]
[new_x + -dy * ratio, new_y + dx * ratio]
when PATH_CURVE_TO
ratio = d / parameterized_path[i]
current_x, current_y = current_point
cx0, cy0 = points[0]
cx1, cy1 = points[1]
cx2, cy2 = points[2]
new_x = current_x * (1 - ratio) * (1 - ratio) * (1 - ratio) +
3 * cx0 * (1 - ratio) * (1 - ratio) * ratio +
3 * cx1 * (1 - ratio) * ratio * ratio +
cx2 * ratio * ratio * ratio
new_y = current_y * (1 - ratio) * (1 - ratio) * (1 - ratio) +
3 * cy0 * (1 - ratio) * (1 - ratio) * ratio +
3 * cy1 * (1 - ratio) * ratio * ratio +
cy2 * ratio * ratio * ratio
dx = -3 * current_x * (1 - ratio) * (1 - ratio) +
3 * cx0 * (1 - 4 * ratio + 3 * ratio * ratio) +
3 * cx1 * ( 2 * ratio - 3 * ratio * ratio) +
3 * cx2 * ratio * ratio
dy = -3 * current_y * (1 - ratio) * (1 - ratio) +
3 * cy0 * (1 - 4 * ratio + 3 * ratio * ratio) +
3 * cy1 * ( 2 * ratio - 3 * ratio * ratio) +
3 * cy2 * ratio * ratio
ratio = y / Math.sqrt(dx ** 2 + dy ** 2)
[new_x + -dy * ratio, new_y + dx * ratio]
when PATH_CLOSE_PATH
[x, y]
end
end
new_path
append_path(transformed_path)
end
private
def parameterize_path(path)
current_point = nil
path.collect do |type, points|
result = 0
case type
when PATH_MOVE_TO
current_point = points[0]
when PATH_LINE_TO
result = current_point.distance(points[0])
current_point = points[0]
when PATH_CURVE_TO
result = current_point.distance(points[0])
result += points[0].distance(points[1])
result += points[1].distance(points[2])
current_point = points[2]
when PATH_CLOSE_PATH
end
result
end
end
end
end
end
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