Code covered by the BSD License  

Highlights from
MATLAB to Point Cloud Library

image thumbnail

MATLAB to Point Cloud Library

by

 

19 Feb 2013 (Updated )

matpcl is pure MATLAB code that allows interfacing with the Point Cloud Library (PCL) tools

loadpcd(fname)
%LOADPCD Load a point cloud from a PCD format file
%
% P = LOADPCD(FNAME) is a set of points loaded from the PCD format
% file FNAME.  
%
% For an unorganized point cloud the columns of P represent the 3D points,
% and the rows are: x, y, z, r, g, b, a depending on the FIELDS in the file.
%
% For an organized point cloud P is a 3-dimensional matrix (HxWxN) where the
% N planes are: x, y, z, r, g, b, a depending on the FIELDS in the file.  This
% format is useful since the planes z, r, g, b, a can be considered as images.
%
% Notes::
% - Only the x y z field format are currently supported
% - The file can be in ascii or binary format, binary_compressed is not
%   supported
%
% See also pclviewer, lspcd, loadpcd.
%
% Copyright (C) 2013, by Peter I. Corke

% TODO
% - handle binary_compressed


function points = loadpcd(fname)

    verbose = true;
    
    fp = fopen(fname, 'r');
    
    
    while true
        line = fgetl(fp);
        
        if line(1) == '#'
            continue;
        end
        
        [field,remain] = strtok(line, ' \t');
        remain = strtrim(remain);
        
        switch field
            case 'VERSION'
                continue;
            case 'FIELDS'
                FIELDS = remain;
            case 'TYPE'
                TYPE = remain;
            case 'SIZE'
                sizes = str2num(remain);
            case 'WIDTH'
                width = str2num(remain);
            case 'HEIGHT'
                height = str2num(remain);
            case 'POINTS'
                npoints = str2num(remain);
            case 'COUNT'
                count = str2num(remain);
            case 'DATA'
                mode = remain;
                break;
            otherwise
                warning('unknown field %s\n', field);
        end
    end
    
    % parse out details of the fields
    %  numFields    the number of fields
    %  sizes        vector of field sizes (in bytes)
    %  types        vector of type identifiers (I U F)
    %  fields       vector of field names (x y z rgb rgba etc)
    numFields = numel(sizes);
    types = cell2mat(regexp(TYPE,'\s+','split'));
    fields = regexp(FIELDS,'\s+','split');
    
    if verbose
        % the doco says height > 1 means organized, but some old files have
        % height = 1 and width > 1
        if height > 1 && width > 1
            organized = true;
            org = 'organized';
        else
            organized = false;
            org = 'unorganized';
        end
        fprintf('%s: %s, %s, <%s> %dx%d\n', ...
            fname, mode, org, FIELDS, width, height);
        fprintf('  %s; %s\n', TYPE, num2str(sizes));
    end
    
    if any(count > 1)
        error('can only handle 1 element per dimension');
    end
    
    switch mode
        case 'ascii'
            format = '';
            for j=1:numFields
                switch types(j)
                    case 'I', typ = 'd';
                    case 'U', typ = 'u';
                    case 'F', typ = 'f';
                end
                format = [format '%' typ num2str(sizes(j)*8)];
            end
            c = textscan(fp, format, npoints);
            points = [];
            for j=1:length(c)
                points = [points; c{j}'];
            end
            if size(points,2) ~= npoints
                error('incorrect number of points in file: was %d, should be %d', ...
                    size(points,2), npoints);
            end
            
        case 'binary'
            format = '';

            if true || all(types == types(1)) && all(sizes == sizes(1))
                % simple case where all fields have the same length and type
                
                % map IUF -> int, uint, float
                switch types(1)
                    case 'I'
                        fmt = 'int';
                    case 'U'
                        fmt = 'uint';
                    case 'F'
                        fmt = 'float';
                end
                
                format = [format '*' fmt num2str(sizes(1)*8)];
                points = fread(fp, [numFields npoints], format);
                
            else
                
                % more complex case where fields have different length and type
                % code contributed by Will
                
                startPos_fp = ftell(fp);
                
                % Just initialize the xyz portion for now
                points = zeros(3, npoints);
                
                for i=1:numFields
                    % map each field sequentially, using fread() skip functionality,
                    % essentially interleaved reading of the file
                    
                    % map IUF -> int, uint, float
                    switch types(i)
                        case 'I'
                            fmt = 'int';
                        case 'U'
                            fmt = 'uint';
                        case 'F'
                            fmt = 'float';
                    end
                    
                    format = ['*' fmt num2str(sizes(i)*8)];
                    fseek(fp, startPos_fp + sum(sizes(1:i-1)), 'bof');
                    data = fread(fp, [1 npoints], format, sum(sizes)-sizes(i));
                    
                    switch fields{i}
                        case 'x'
                            points(1,:) = data;
                        case 'y'
                            points(2,:) = data;
                        case 'z'
                            points(3,:) = data;
                        case {'rgb', 'rgba'}
                            points(4,:) = data;
                    end
                end
                
            end
            
        case 'binary_compressed'
            % binary part of the file contains:
            %  compressed size of data (uint32)
            %  uncompressed size of data (uint32)
            %  compressed data
            %  junk
            compressed_size = fread(fp, 1, 'uint32');
            uncompressed_size = fread(fp, 1, 'uint32');
            compressed_data = fread(fp, compressed_size, 'uint8')';

            uncompressed_data = lzfd(compressed_data);
            if length(uncompressed_data) ~= uncompressed_size
                error('decompression error');
            end
            
            % the data is stored unpacked, that is one field for all points,
            % then the next field for all points, etc.
            
            start = 1;
            for i=1:numFields
                len = sizes(i)*npoints;
                switch types(1)
                    case 'I'
                        fmt = 'int32';
                    case 'U'
                        fmt = 'uint32';
                    case 'F'
                        fmt = 'single';
                end
                field = typecast(uncompressed_data(start:start+len-1), fmt);
                start = start + len;
                
                switch fields{i}
                    case 'x'
                        points(1,:) = field;
                    case 'y'
                        points(2,:) = field;
                    case 'z'
                        points(3,:) = field;
                    case {'rgb', 'rgba'}
                        points(4,:) = field;
                end
            end           
            
        otherwise
            error('unknown DATA mode: %s', mode);
    end
    
    if size(points,1) > 3
        % convert RGB from float to rgb
        rgb = typecast(points(4,:), 'uint32');
        switch FIELDS
            case 'x y z rgb'
                R = double(bitand(255, bitshift(rgb, 16))) /255;
                G = double(bitand(255, bitshift(rgb, 8))) /255;
                B = double(bitand(255, rgb)) /255;
                points = [points(1:3,:); R; G; B];
                
            case 'x y z rgba'
                R = double(bitand(255, bitshift(rgb, 24))) /255;
                G = double(bitand(255, bitshift(rgb, 16))) /255;
                B = double(bitand(255, bitshift(rgb, 8))) /255;
                A = double(bitand(255, rgb)) /255;
                points = [points(1:3,:); R; G; B; A];
        end
    end
    
    if organized
        % data is an organized point cloud, rearrange it into planes
        
        points = permute( reshape( shiftdim(points, 1), width, height, []), [2 1 3]);
    end
               
    fclose(fp);

Contact us