augmentData.m

function B = augmentData(A)
% Apply random horizontal flipping, and random X/Y scaling. Boxes that get
% scaled outside the bounds are clipped if the overlap is above 0.25. Also,
% jitter image color.
B = cell(size(A));

I = A{1};
sz = size(I);
if numel(sz)==3 && sz(3) == 3
    I = jitterColorHSV(I,...
        'Contrast',0.2,...
        'Hue',0,...
        'Saturation',0.1,...
        'Brightness',0.2);
end

% Randomly flip and scale image.
tform = randomAffine2d('XReflection',true,'Scale',[1 1.1],'Rotation',[-20 20]);  
rout = affineOutputView(sz,tform,'BoundsStyle','CenterOutput');    
B{1} = imwarp(I,tform,'OutputView',rout);

% Sanitize boxes, if needed.
A{2} = helperSanitizeBoxes(A{2}, sz);
    
% Apply same transform to boxes.
[B{2},indices] = bboxwarp(A{2},tform,rout,'OverlapThreshold',0.25);    
B{3} = A{3}(indices);
    
% Return original data only when all boxes are removed by warping.
if isempty(indices)
    B = A;
end
end
% helperSanitizeBoxes Sanitize box data.
% If none of the boxes are valid, this function passes the data through to
% enable downstream processing to issue proper errors.
function boxes = helperSanitizeBoxes(boxes, ~)
persistent hasInvalidBoxes
valid = all(boxes > 0, 2);
if any(valid)
    if ~all(valid) && isempty(hasInvalidBoxes)
        % Issue one-time warning about removing invalid boxes.
        hasInvalidBoxes = true;
        warning('Removing ground truth bouding box data with values <= 0.')
    end
    boxes = boxes(valid,:); 
end
end