Put timestamps on Image's name into a bag

asked 2017-08-23 03:55:31 -0500

trinamntn08 gravatar image

I have a folder containing sequence of images with the timestamp which is also the name of each image. I create a bag containing "image topic" , and i want to set header of this topic by these timestamps. But when i run this bag , i think speed of this topic is really fast; It runs just within 2s when normally , the sequence of image(30Hz) runs within 30s.

def getImageFilesFromDir(dir):
'''Generates a list of files from the directory'''
image_files = list()
timestamps = list()
if os.path.exists(dir):
    for path, names, files in os.walk(dir):
        for f in files:
            if os.path.splitext(f)[1] in ['.bmp', '.png', '.jpg']:
                image_files.append( os.path.join( path, f ) )
                timestamps.append(os.path.splitext(f)[0]) 
#sort by timestamp
sort_list = sorted(zip(timestamps, image_files))
image_files = [file[1] for file in sort_list]
return image_files
def loadImageToRosMsg(filename):
image_np = cv2.imread(filename, cv2.IMREAD_GRAYSCALE)

timestamp_nsecs = os.path.splitext(os.path.basename(filename))[0]
timestamp = rospy.Time( secs=int(timestamp_nsecs[0:-9]), nsecs=int(timestamp_nsecs[-9:]) )

rosimage = Image()
rosimage.header.stamp = timestamp
rosimage.height = image_np.shape[0]
rosimage.width = image_np.shape[1]
rosimage.step = rosimage.width  #only with mono8! (step = width * byteperpixel * numChannels)
rosimage.encoding = "mono8"
rosimage.data = image_np.tostring()

return rosimage, timestamp
try:
bag = rosbag.Bag(parsed.output_bag, 'w')

#write images
camfolders = getCamFoldersFromDir(parsed.folder)
for camfolder in camfolders:
    camdir = parsed.folder + "/{0}".format(camfolder)
    image_files = getImageFilesFromDir(camdir)
    for image_filename in image_files:
        image_msg, timestamp = loadImageToRosMsg(image_filename)
        bag.write("/{0}/image_raw".format(camfolder), image_msg, timestamp)
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Comments

You could have each iteration sleep the time difference between the last image and the current one, but why would you want it to run slower?

lucasw gravatar image lucasw  ( 2017-08-23 17:48:48 -0500 )edit

in fact, i put this as the input of SLAM system, the frequency of images reaches normally 30 Hz. What i don't understand is that i put the timestamp of each image in the header of this bag. it means that frequency have to be 30Hz if all things are right.

trinamntn08 gravatar image trinamntn08  ( 2017-08-24 02:27:26 -0500 )edit

I misunderstood the question before. Update the question with a list of filenames (ls -1 in a camera folder) and the timestamps that were put into the bag (rostopic echo /folder/image_raw/header/stamp while playing the bag) then it could be seen if your code is good.

lucasw gravatar image lucasw  ( 2017-08-24 10:13:27 -0500 )edit
1

Also the indentation in your quoted code is messed up, making it hard to read.

lucasw gravatar image lucasw  ( 2017-08-24 10:13:54 -0500 )edit