Creating scenes with spatial frequency (harmonic) patterns
Scenes comprising harmonic patterns and sums of harmonics are frequently used to evaluate image systems. sceneCreate generates these patterns.
The parameters set the frequency, contrast, phase, angle, row and col size of the harmonic. The frequency is cycles/image, so if you know the horizontal field of view, just divide to obtain cycles per degree.
See also: sceneCreate
Copyright: ImagEval Consulting 2011
Contents
ieInit
The harmonic parameters
params.freq = 1; params.contrast = 1; params.ph = 0; params.ang= 0; params.row = 128; params.col = 128; params.GaborFlag=0; % The basic call to sceneCreate with the params is [scene,params] = sceneCreate('harmonic',params); ieAddObject(scene); sceneWindow;
The sum of two (or more) harmonics
% Set the slots for freq, contrast, ang, and ph to vectors of the % same length to define the multiple harmonics. params.freq = [1 5]; % spatial frequencies of 1 and 5 params.contrast = [0.2, 0.6]; % contrast of the two frequencies params.ang = [0, 0]; % orientations params.ph = [0 pi/3]; % phases TwoFreq = sceneCreate('harmonic',params); ieAddObject(TwoFreq); sceneWindow;
Vary the orientation of the two harmonics
params.freq = [2 5]; % spatial frequencies of 1 and 5 params.contrast = [0.6, 0.6]; % contrast of the two frequencies params.ang = [pi/4, -pi/4]; % orientations params.ph = [0 0]; % phase TwoFreq = sceneCreate('harmonic',params); ieAddObject(TwoFreq); sceneWindow;
another example
params.freq = [5 5]; % spatial frequencies of 1 and 5 params.contrast = [0.6, 0.6]; % contrast of the two frequencies params.ang = [pi/4, -pi/4]; % orientations params.ph = [0 0]; % phase TwoFreq = sceneCreate('harmonic',params); ieAddObject(TwoFreq); sceneWindow;
