PYRUP - Bottom-up hierarchical decomposition.

Contents

Description

Perform a bottom-up hierarchical decomposition (resolution increases) of an image into a pyramid using the function EXPAND2D; it also implements the classical bottom-up Laplacian Pyramid of [BA83].

Syntax

  Ip = PYRUP(I);
  [Ip,Ep] = PYRUP(I, nlevels, stack, filter, order);

Inputs

See function PYRDOWN.

Note: default nlevels=1, ie. the pyramid has one level only.

Outputs

Ip : output pyramid; if stack==true, Ip is a cell of nlevels images, each being an expanded version of the previous level; if stack=false, Ip is just the last level of the pyramid.

Er : (optional) error of the last level of the pyramid, computed as error=signal­REDUCE2D(Ip).

See also

Ressembles: PYRDOWN, EXPAND2D, REDUCE2D. Requires: PYRUP_BASE, REDUCE2D_BASE.

Function implementation

function [Ip, varargout] = pyrup(I,varargin)

check if possible

error(nargchk(1, 13, nargin, 'struct'));
error(nargoutchk(1, 2, nargout, 'struct'));

if ~isnumeric(I)
    error('pyrup:inputparameter','a matrix is required in input');
end

parsing parameters

p = createParser('PYRUP');
p.addOptional('nlevels',1, @(x)isscalar(x) && x>=1);
p.addOptional('stack', true, @(x)islogical(x));
p.addOptional('filter','cspl', @(x)ischar(x) && ...
    any(strcmpi(x,{'lpl','spl','spl2','cspl','cspl2'})));
p.addOptional('order',3, @(x)isscalar(x) && x>0);

% parse and validate all input arguments
p.parse(varargin{:});
p = getvarParser(p);

checking parameters

if any(strcmpi(p.filter,{'cspl','cspl2''spl''spl2'}))
    if ~exist('expand2d_mex','file')
        error('pyrup:errorlibrary', ...
            'mex file expand2d_mex required for spline based pyramid');
    elseif isempty(p.order)
        p.order = 3;
    end
elseif ~isempty(p.order)
    warning('pyrup:warninginput', ...
        'input variable ''order'' ignored with Laplacian pyramid');
    p.order = [];
end

if (any(strcmpi(p.filter,{'cspl','cspl2'})) && ~ismember(p.order,[0,1,2,3,4])) || ...
        (strcmpi(p.filter,'spl') && ~ismember(p.order,[0,1,2,3])) || ...
        (strcmpi(p.filter,'spl2') && ~ismember(p.order,[0,1,3,5]))
    error('pyrup:inputerror', ...
        'check compatibility of filter and order variables');
end

main computation

Ip = pyrup_base(I, p.nlevels, p.stack, p.filter, p.order);

if nargout==2
    % take the last level
    if p.stack,   Io = Ip{p.nlevels};
    else          Io = Ip;       end;
    for i=1:p.nlevels
        [Io,Er] = reduce2d_base( Io, p.filter, p.order ); % expand
    end
    varargout{i} = Er;
end

end % end of pyrup