Access images from within a ROSBAG

I have a rosbag which contains several sets of images from an Intel D435 camera (I have it in both compressed and uncompressed form (compressed data shown))

BAG =

BagSelection with properties:

           FilePath: '/home/Documents/20180628_212236.orig.bag'
          StartTime: 1.0000e-09
            EndTime: 8.0653
        NumMessages: 2619
    AvailableTopics: [75×3 table]
    AvailableFrames: {0×1 cell}
        MessageList: [2619×4 table]

I think I want the data stored in

 /device_0/sensor_0/Depth_0/image/data (see below)

Can anyone please advise how I access the image data. Thanks

>>BAG.AvailableTopics

ans =

75×3 table

                                                                       NumMessages           MessageType                                                                                                                                                              MessageDefinition                                                                                                                                                    
                                                                       ___________    _________________________    ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

    /device_0/info                                                           7        diagnostic_msgs/KeyValue     'char Key↵char Value↵'                                                                                                                                                                                                                                                                                                  
    /device_0/sensor_0/Depth_0/image/data                                   71        sensor_msgs/Image            'std_msgs/Header Header↵  uint32 Seq↵  Time Stamp↵  char FrameId↵uint32 Height↵uint32 Width↵char Encoding↵uint8 IsBigendian↵uint32 Step↵uint8[] Data↵'                                                                                                                                                                  
    /device_0/sensor_0/Depth_0/image/metadata                              781        diagnostic_msgs/KeyValue     'char Key↵char Value↵'                                                                                                                                                                                                                                                                                                  
    /device_0/sensor_0/Depth_0/info                                          1        realsense_msgs/StreamInfo    'uint32 Fps↵char Encoding↵logical IsRecommended↵'                                                                                                                                                                                                                                                                       
    /device_0/sensor_0/Depth_0/info/camera_info                              1        sensor_msgs/CameraInfo       'std_msgs/Header Header↵  uint32 Seq↵  Time Stamp↵  char FrameId↵uint32 Height↵uint32 Width↵char DistortionModel↵double[] D↵double[9] K↵double[9] R↵double[12] P↵uint32 BinningX↵uint32 BinningY↵sensor_msgs/RegionOfInterest Roi↵  uint32 XOffset↵  uint32 YOffset↵  uint32 Height↵  uint32 Width↵  logical DoRectify↵'
    /device_0/sensor_0/Depth_0/tf/0                                          1        geometry_msgs/Transform      'geometry_msgs/Vector3 Translation↵  double X↵  double Y↵  double Z↵geometry_msgs/Quaternion Rotation↵  double X↵  double Y↵  double Z↵  double W↵'                                                                                                                                                                     
    /device_0/sensor_0/Infrared_1/image/data                                71        sensor_msgs/Image            'std_msgs/Header Header↵  uint32 Seq↵  Time Stamp↵  char FrameId↵uint32 Height↵uint32 Width↵char Encoding↵uint8 IsBigendian↵uint32 Step↵uint8[] Data↵'                                                                                                                                                                  
    /device_0/sensor_0/Infrared_1/image/metadata                           781        diagnostic_msgs/KeyValue     'char Key↵char Value↵'                                                                                                                                                                                                                                                                                                  
    /device_0/sensor_0/Infrared_1/info                                       1        realsense_msgs/StreamInfo    'uint32 Fps↵char Encoding↵logical IsRecommended↵'                                                                                                                                                                                                                                                                       
    /device_0/sensor_0/Infrared_1/info/camera_info                           1        sensor_msgs/CameraInfo       'std_msgs/Header Header↵  uint32 Seq↵  Time Stamp↵  char FrameId↵uint32 Height↵uint32 Width↵char DistortionModel↵double[] D↵double[9] K↵double[9] R↵double[12] P↵uint32 BinningX↵uint32 BinningY↵sensor_msgs/RegionOfInterest Roi↵  uint32 XOffset↵  uint32 YOffset↵  uint32 Height↵  uint32 Width↵  logical DoRectify↵'
    /device_0/sensor_0/Infrared_1/tf/0                                       1        geometry_msgs/Transform      'geometry_msgs/Vector3 Translation↵  double X↵  double Y↵  double Z↵geometry_msgs/Quaternion Rotation↵  double X↵  double Y↵  double Z↵  double W↵'                                                                                                                                                                     
    /device_0/sensor_0/info                                                  1        diagnostic_msgs/KeyValue     'char Key↵char Value↵'                                                                                                                                                                                                                                                                                                  
    /device_0/sensor_0/option/Asic Temperature/description                   1        std_msgs/String              'char Data↵'                                                                                                                                                                                                                                                                                                            
    /device_0/sensor_0/option/Asic Temperature/value                         1        std_msgs/Float32             'single Data↵'                                                                                                                                                                                                                                                                                                          
    /device_0/sensor_0/option/Depth Units/description                        1        std_msgs/String              'char Data↵'                                                                                                                                                                                                                                                                                                            
    /device_0/sensor_0/option/Depth Units/value                              1        std_msgs/Float32             'single Data↵'                                                                                                                                                                                                                                                                                                          
    /device_0/sensor_0/option/Emitter Enabled/description                    1        std_msgs/String              'char Data↵'                                                                                                                                                                                                                                                                                                            
    /device_0/sensor_0/option/Emitter Enabled/value                          1        std_msgs/Float32             'single Data↵'                                                                                                                                                                                                                                                                                                          
    /device_0/sensor_0/option/Enable Auto Exposure/description               1        std_msgs/String              'char Data↵'                                                                                                                                                                                                                                                                                                            
    /device_0/sensor_0/option/Enable Auto Exposure/value                     1        std_msgs/Float32             'single Data↵'                                                                                                                                                                                                                                                                                                          
    /device_0/sensor_0/option/Error Polling Enabled/description              1        std_msgs/String              'char Data↵'

Answer 1

[MP]

To answer my own question (just in case anyone is interested) -------------------------------

function ROSBAG_Reader

%%%%%%%%%% Hard coded bits %%%%%%%%%%%%%%%%%%%%%%%

startT = 5 %start time for image extraction

endT = 6 % end time for image extraction

depthLim =1000; %remove all depth data greater than depthLim

fn = ('test.bag');

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%image data stored in the following

dataType = {'/device_0/sensor_0/Depth_0/image/data';...

    '/device_0/sensor_0/Infrared_1/image/data';...

    '/device_0/sensor_1/Color_0/image/data'};

% not interested in infrared data

for i=1:2:3

    dataT=dataType{i}

    bag = rosbag(fn)
    bagselect1 = select(bag, 'Topic', dataT)
    bagselect2 = select(bag, 'Time', [startT  endT], 'Topic', dataT)
    bagselect2.AvailableTopics{1,end}
    bagselect3 = select(bagselect2, 'Time', [startT  endT])
    msgs = readMessages(bagselect3);
    msgs{1}
    for j=1:size(msgs,1)
        [img,alpha] = readImage(msgs{1});
        try
            figure(1)
            imshow(img,[min(min(img)) max(max(img))/10]);colormap(jet)
            img=double(img);
            img(img>depthLim)=0; 
            img(img==0)=NaN; % get rid of spurious daa from mesh plot
            figure(2); mesh(img)
        catch
            figure(3)
            imshow(img)
        end
        clear img
    end
end

[Joseph Seklawy]

How did you find this out?