Rescale.m

function img = Rescale(img, scale)
%RESCALE  - resize image
%
%	 usage:  img = Rescale(img, scale)
%
% resizes input single-plane image per specified SCALE factor
% output IMG matches class of input (double, uint8, etc.)
%
% see also RESIZE

% mkt 12/15

% parse args

if nargin < 2, eval('help Rescale'); return; end;
if ndims(img) > 2, 
	error('operates on single-plane images only'); 
end;
if ~isnumeric(scale) || prod(size(scale))>1 || scale<=0,
	error('scale factor must be numeric scalar value > 0');
end;

urClass = class(img);
img = im2double(img);

% filter when scale < 1 to avoid aliasing
if scale < 1,
	[ih, iw] = size(img);
	mih = floor(ih*scale); miw = floor(iw*scale);
	h = fir1(10, mih/ih)' * fir1(10, miw/iw);
	img = filter2(h, img);
end;

% build interpolation indices
[ih, iw] = size(img);
mih = floor(ih*scale);
miw = floor(iw*scale);
[x,y] = meshgrid(1:(iw-1)/(miw-1):iw, 1:(ih-1)/(mih-1):ih);

% interpolate
img = interp2(img, x, y, 'cubic');

% adjust output class
switch urClass,
	case 'uint8', img = im2uint8(img);
	case 'single', img = im2single(img);
	otherwise,
end;