stimInitialize.m

function stimParams = stimInitialize(experimentSpecs, whichSite, stimDiameterDeg)
% Get the data structure for an example stimulus. The fields will be
% populated for actual stimuli.
%
% stimParams = stimInitialize(experimentSpecs, 1, 16.6);

displayParameters       = loadDisplayParams(experimentSpecs.displays{whichSite});

screenHeightInPixels    = displayParameters.numPixels(2);

screenWidthInPixels     = displayParameters.numPixels(1);

screenHeightInDegrees   = pix2angle(displayParameters, screenHeightInPixels);

fractionOfScreenToUse   = stimDiameterDeg/screenHeightInDegrees;

stimSizeInPixels        = fractionOfScreenToUse * screenHeightInPixels;

% We want our image size to be an even number of pixels for subsequent
% image processing
nearestEven = @(x) round(x/2)*2;
stimSizeInPixels = nearestEven(stimSizeInPixels);

% The images may be larger than the screen, in which case we need to crop
cropSizeInPixels = min(stimSizeInPixels, screenHeightInPixels);

% colormap: 1:256 (gamma table is controlled separately)
stimulus.cmap    = (ones(3,1)*(1:256))'; 

% Which part of the image to use? (Source rect)
left   = (stimSizeInPixels - cropSizeInPixels)/2;
top    = (stimSizeInPixels-cropSizeInPixels)/2;
right  = stimSizeInPixels - left; 
bottom = stimSizeInPixels - top;

stimulus.srcRect =  [left, top, right, bottom];

% Where to put it? (Destination rect)
left   = (screenWidthInPixels - cropSizeInPixels)/2;
top    = (screenHeightInPixels - cropSizeInPixels)/2;
right  = screenWidthInPixels - left; 
bottom = screenHeightInPixels - top;

stimulus.destRect = [left, top, right, bottom];

% a blank image
stimulus.images = uint8(zeros(stimSizeInPixels)+127);

stimulus.seqtiming  = [];
stimulus.seq        = [];
stimulus.fixSeq     = [];


stimParams.stimulus         = stimulus;
stimParams.display          = displayParameters;
stimParams.modality         = experimentSpecs.modalities{whichSite};
stimParams.experimentSpecs  = experimentSpecs(whichSite,:);
stimParams.site             = experimentSpecs.Row{whichSite};
return