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executable file 90 lines (78 sloc) 2.344 kb
% IM = mkSquare(SIZE, PERIOD, DIRECTION, AMPLITUDE, PHASE, ORIGIN, TWIDTH)
% or
% IM = mkSine(SIZE, FREQ, AMPLITUDE, PHASE, ORIGIN, TWIDTH)
%
% Compute a matrix of dimension SIZE (a [Y X] 2-vector, or a scalar)
% containing samples of a 2D square wave, with given PERIOD (in
% pixels), DIRECTION (radians, CW from X-axis, default = 0), AMPLITUDE
% (default = 1), and PHASE (radians, relative to ORIGIN, default = 0).
% ORIGIN defaults to the center of the image. TWIDTH specifies width
% of raised-cosine edges on the bars of the grating (default =
% min(2,period/3)).
%
% In the second form, FREQ is a 2-vector of frequencies (radians/pixel).
% Eero Simoncelli, 6/96.
% TODO: Add duty cycle.
function [res] = mkSquare(sz, per_freq, dir_amp, amp_phase, phase_orig, orig_twidth, twidth)
%------------------------------------------------------------
%% OPTIONAL ARGS:
if (prod(size(per_freq)) == 2)
frequency = norm(per_freq);
direction = atan2(per_freq(1),per_freq(2));
if (exist('dir_amp') == 1)
amplitude = dir_amp;
else
amplitude = 1;
end
if (exist('amp_phase') == 1)
phase = amp_phase;
else
phase = 0;
end
if (exist('phase_orig') == 1)
origin = phase_orig;
end
if (exist('orig_twidth') == 1)
transition = orig_twidth;
else
transition = min(2,2*pi/(3*frequency));
end
if (exist('twidth') == 1)
error('Too many arguments for (second form) of mkSine');
end
else
frequency = 2*pi/per_freq;
if (exist('dir_amp') == 1)
direction = dir_amp;
else
direction = 0;
end
if (exist('amp_phase') == 1)
amplitude = amp_phase;
else
amplitude = 1;
end
if (exist('phase_orig') == 1)
phase = phase_orig;
else
phase = 0;
end
if (exist('orig_twidth') == 1)
origin = orig_twidth;
end
if (exist('twidth') == 1)
transition = twidth;
else
transition = min(2,2*pi/(3*frequency));
end
end
%------------------------------------------------------------
if (exist('origin') == 1)
res = mkRamp(sz, direction, frequency, phase, origin) - pi/2;
else
res = mkRamp(sz, direction, frequency, phase) - pi/2;
end
[Xtbl,Ytbl] = rcosFn(transition*frequency,pi/2,[-amplitude amplitude]);
res = pointOp(abs(mod(res+pi, 2*pi)-pi),Ytbl,Xtbl(1),Xtbl(2)-Xtbl(1),0);
% OLD threshold version:
%res = amplitude * (mod(res,2*pi) < pi);
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