digitalimageprocessing2019/Assignment_1/saveasppm.m

function saveasppm(x, filename, K)
%saveasppm encodes an image as PPM and saves it to the disk
%   Usage saveasppm(x, filename, K), where:
%       Inputs
%       - x is the input image
%       - filename is the path and filename of the file where the resulting
%           PPM image is going to be saved
%       - K is the maximum value of brightness

    file = fopen(filename, 'w');
    
    fwrite(file, 'P6');
    fwrite(file, ' ');
    fwrite(file, int2str(size(x.red, 1)));
    fwrite(file, ' ');
    fwrite(file, int2str(size(x.red, 2)));
    fwrite(file, ' ');
    fwrite(file, int2str(K));
    fwrite(file, newline);
    
    if K < 256
        precision = 'integer*1';
        precisionBytes = 1;
        machinefmt = 'l';
    else
        precision = 'integer*2';
        precisionBytes = 2;
        machinefmt = 'b';
    end
    
    for row = 1:size(x.red, 1)
        for column = 1:size(x.red, 2)
            fwrite(file, x.blue(row, column), precision, machinefmt);
            fwrite(file, x.green(row, column), precision, machinefmt);
            fwrite(file, x.red(row, column), precision, machinefmt);
        end
    end

    fclose(file);
end