Convert SVHN metadata .mat file format to .json

svhn_convert_json.m

function svhn_convert_json(path)
% convert .mat to json files

%% Create .json file

if isempty(path)
    error('Must specify a path to the dataset')
end


%% Train

fprintf('Processing train data (1/3):\n');
convert_to_json(path, 'train');

%% Test

fprintf('Processing test data (2/3):\n');
convert_to_json(path, 'test');

%% Extra

fprintf('Processing extra data (3/3):\n');
convert_to_json(path, 'extra');

%% Script complete
fprintf('Convert SVHN to json script complete. \n')
end


function convert_to_json(path, setName)
%% load annotation file

fprintf('==> Load annotation files... ')
data = load(strcat(path,'/',setName,'/digitStruct.mat'));
fprintf('Done.\n')

%% open file
save_path = strcat(path,'/',setName,'.json');
fprintf('==> Open file: %s \n', save_path)
fileID = fopen(save_path,'w');

%% cycle all data and save to file (.json)
fprintf('==> Parsing annotations to the .json file... ')
fprintf(fileID, '"[');

% add field name + bbox
nfiles = size(data.digitStruct,2);
for i=1:1:nfiles
    fprintf(fileID, '{\\"name\\": \\"%s\\", \\"bbox\\": [', data.digitStruct(i).name);
for ibb =1:1:size(data.digitStruct(i).bbox,2)
        fprintf(fileID, '{\\"height\\": %d,', data.digitStruct(i).bbox(ibb).height);
        fprintf(fileID, '\\"width\\": %d,', data.digitStruct(i).bbox(ibb).width);
        fprintf(fileID, '\\"left\\": %d,', data.digitStruct(i).bbox(ibb).left);
        fprintf(fileID, '\\"top\\": %d,', data.digitStruct(i).bbox(ibb).top);
        fprintf(fileID, '\\"label\\": %d}', data.digitStruct(i).bbox(ibb).label);
        if ibb < size(data.digitStruct(i).bbox,2)
            fprintf(fileID, ',');
        end
    end
    fprintf(fileID, ']}');
    
    if i < nfiles
        fprintf(fileID, ',');
    end
end

fprintf(fileID, ']"');
fclose(fileID);
fprintf('Done.\n\n')

end

end