Labeling Tool User Manual En

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Labeling Tool - User Manual
Ricardo Ribeiro (ribeiro@isr.ist.utl.pt)
October 28, 2014

Contents
1 Software version

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2 Introduction

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3 Instalation and compilation of the tool
3.1 Obtaining the tool (SVN) . . . . . . . . . . . . . . . . . . . . . .
3.2 Dependencies and supported OS’s . . . . . . . . . . . . . . . . .
3.3 Build the tool . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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4 Tool execution
4.1 Command line . .
4.2 Video file . . . . .
4.3 Labeling file . . . .
4.4 Autosave e backup

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5 Using the tool
5.1 General use . . . . . . . . .
5.1.1 Help (“h” key) . . .
5.1.2 Keyboard . . . . . .
5.1.3 Mouse . . . . . . . .
5.1.4 Save . . . . . . . . .
5.1.5 Exit . . . . . . . . .
5.1.6 Navigate the video .
5.1.7 Zoom . . . . . . . .
5.1.8 Window size . . . .
5.1.9 Object ID’s . . . . .
5.2 Labels . . . . . . . . . . . .
5.2.1 Label anatomy . . .
5.2.2 Label types . . . . .
5.2.3 Label creation . . .
5.2.4 Label deletion . . . .
5.2.5 Label modification .
5.2.6 Finalizing the labels
5.3 Automations . . . . . . . .
5.3.1 Copy . . . . . . . . .
5.3.2 Copy with search . .
5.3.3 Linear interpolation

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1

5.4
5.5

5.3.4 Search in a sequence . . . . .
Label confirmation and verification .
Visual Help . . . . . . . . . . . . . .
5.5.1 Dynamic range maximization

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15

List of Figures
1
2
3
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1

Help . . . . . . . . . . .
Keyboard Map . . . . .
Information . . . . . . .
Zoom . . . . . . . . . .
Object ID’s . . . . . . .
Label types. . . . . . . .
Ways to use the mouse.
Linear interpolation . .
Search in a sequence . .

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Software version

This manual documents the version 0.1.1 of the labeling tool (labelingtool v0.1.1).

2

Introduction

For the training and testing of vision algorithms it is necessary to use image
sequences that where manually labeled.
The labeling task consists in tagging all objects in the image with a rectangle.
Such operation needs to be done manually since the labeling is to be considered
as the ground truth against which the results of the algorithms are compared.
Any kind of error in the labeling process will have a negative impact in the
performance of the algorithms and will compromise the reliability of the test
results.
This manual process is quite heavy and long, specially if the number of
images is large, as normally is the case for video sequences. For that reason,
this tools was developed aiming to alleviate the weight of this task. This was
achieved in several ways.
One way was to create an very light and fast interface that minimizes the
number of operations necessary for each label. This was achieved by developing
this tool in C++ (the OpenCV libraries where used). There was care into
making the execution of all operations the fastest possible so that the user of
the tool can immediately see the result of the commands executed, even if the
commands are given in fast sequence. The manual tools that existed previously,
developed in Matlab, where too slow.
Another way to alleviate the users work was to provide automatic mechanisms to create the labels without dispensing the user of the task of adjusting,
at least, of verifying them. These automations try to place new label the closest
possible of the intended final position for them. The user only needs to do small
adjustments or to confirm the labels correctness.

2

This tool is generic and can be applied to label any kind of object in any
kind of images. Its limitation is that only rectangular labels are supported.

3

Instalation and compilation of the tool

3.1 Obtaining the tool (SVN)
The tool is in the folder
devel/tools/labeling_tool
in the Seagull SVN repository located at the ISR servers. To download the tool
use the command:

svn checkout svn://svn.isr.ist.utl.pt/seagull/devel/tools/labeling_tool

3.2 Dependencies and supported OS's
This tool depends on the OpenCV libraries which need to be installed before
build time.
To build the tool is also necessary to have cmake installed.
The tool was developed in linux, so it compiles and works well in this operating system.
It was also compiled and tested in Mac OS X. This version is usable but has
some problems in the window resizing features described in subsection 5.1.8.

3.3 Build the tool
To build the tool use the following commands:
cd labeling_tool
mkdir build
cd build
cmake ..
make

4

Tool execution

4.1 Command line
The tool is executed inside the build folder (see section 3.3) using the command
./labeling_tool [options] 
To obtain help use
./labeling_tool -h

3

4.2 Video le
The video file can be in any format supported by OpenCV (examples: .mpg,
.avi, .mkv, etc.). Name the file in the command line. For example:
./labeling_tool lanchaArgos_clip1.avi
If the file is in a different folder, then also include the path.
./labeling_tool videos/lanchaArgos_clip1.avi

4.3 Labeling le
By default, the filename where the labels are saved is the same as the video file
with its extension replace by .gt.txt. For example, the command
./labeling_tool videos/lanchaArgos_clip1.avi
creates the labeling file
videos/lanchaArgos_clip1.gt.txt
Alternatively, a different filename can be specified using the -d option.
./labeling_tool -d labels.gt.txt lanchaArgos_clip1.avi
The labeling file format (labelingtool v0.1) is a simple text file with one line per
label. Each line has the following format:
      <1(temporary)/0(final)>
The file format is also documented in the tools’s help.
./labeling_tool -h

4.4 Autosave e backup
Every 30 seconds a backup file with extension .autosave is saved with all labels
and changes made so far. This file is deleted when the program exits normally.
There is also a backup file that is coppied from the original file before the
program saves the new file. This backup file has the same filename as the original
but with a tilde (~) added (example: labels.gt.txt~).

5

Using the tool

5.1 General use
5.1.1

Help (“h” key)

An help screen is always available at any moment (Figure 1). It contains all the
key shortcuts available and a brief description of the corresponding commands.
Press “h” to call the help screen and press “h” again to exit from it.
The tool continues to work normally even when the help screen is active.
The screen itself is translucent and the mouse and keyboard are still active, so
the user can keep working while seeing the help screen.
4

Figure 1: Help - Press the “h” key.
5.1.2

Keyboard

The commands available in the tool are almost all executed through the use
of the keyboard (see Figure 2). There are keys or combinations of keys to
execute all operations. Ergonomics was taken into account when assigning the
shortcut keys so that the number of necessary movements of the user hands and
fingers was minimized, not only for single command but also for sequences of
commands.
The keyboard map from Figure 2 is also available at
labeling_tool/doc/keyboard_map.pdf
in a file ready to be printed for reference.
Note: This tool was developed based on the Portuguese keyboard layout
from Portugal. For other keyboard layouts the commands may be located differently.
5.1.3

Mouse

It is possible to use the mouse, but that option is more useful for large movements, which are rare. It is preferable to keep the hands on the keyboard instead
of waisting time moving the hand between the mouse and the keyboard.
The mouse can be used to move or to modify a label by clicking and dragging.
The point where the user clicks defines the operation. For more information see
subsection 5.2.5.
5.1.4

Save

Contrary to what is usual, there is no specific command to save the labels file
because the file is automatically saved when the program exits (when the user

5

Figure 2: Keyboard map showing all available the commands (this map is available at labeling_tool/doc/keyboard_map.pdf).
presses the ESC key).1
Every 30 seconds, a file with .autosave extension is saved with all current
changes. This file is deleted when the program exits normally.
5.1.5

Exit

Press the ESCAPE key. The labels file is saved automatically.
5.1.6

Navigate the video

There are many key to go forward and backward on the video file. The following
is available:
• play and stop the video - SPACE key
• seek backward/forward by 1 frame - “,” and “.” keys
• seek backward/forward by 10 frames - “m” and “-” keys
• seek backward/forward by 100 frames - “;” and “:” keys ( i.e., SHIFT +
“,” and SHIFT + “.” )
• goto first frame - “M” key ( i.e., SHIFT + “m” )
• goto last frame - “_” key ( i.e., SHIFT + “-” )
Is is also possible to find the previous/next frame which:
• contains a temporary label - SHIFT + “k” and SHIFT + “l”
1 Tip:

to exit the program without saving go to the terminal where the program was

started and press CTRL+c. In this way the program is immediately killed without having
the opportunity to save the le.

6

Figure 3: Information - by pressing the “v” key the frame number and object
ID is shown in the upper right corner of the image.
• contains a final label - “k” and “l”
Press “v” to show the current frame number in the top right corner of the image
(Figure 3).
5.1.7

Zoom

In order to achieve better accuracy, is useful to see in detail the area where the
label is placed. Pressing the “x” key cyclically changes the zoom between 1 (no
zoom), 2 and 4 times zoom (Figure 4). All commands work independently of
the zoom selected.
The zoom is automatically centered around the marked label. Any adjustment to the label causes a new centering.
Note: This command does not change the window size. To do that see
subsection 5.1.8.
Warning1: Due to the autocentering feature, the use of the mouse to change
the label while zooming can be cumbersome.
Warning2: When seeking the video with the zoom enabled, the image
can jump unpredictably. This behavior is normal and happens when a frame
does not have a defined label, making the centering impossible in that frame.
Solution: choose 1x zoom or ignore the image jumps.
5.1.8

Window size

(See subsection 3.2 about the limitation in Mac OS X.)
The keys “7”, “8” e “9” allow to set the size of the window to half, full and
double size compared to the original video size. This window size is independent
of the zoom selected (see subsection 5.1.7).
It is also possible to put the window in full screen by pressing the “0” key.
In this mode the use of the screen is maximized.

7

(a) 1x

(b) 2x

(c) 4x

Figure 4: Zoom - press the “z” key to cyclically change the zoom:
1x→2x→4x(→1x→etc.).

8

Figure 5: Object ID’s - pressing “x” will show the ID’s inside the label rectangles.
Pressing “v” will show the current ID in the upper right corner (in this case,
ID=0).
Note: To obtain a real pixel representation of the video on screen choose
the original windows size (“8” key) and select 1x zoom (subsection 5.1.7).
Note: By default, the tools starts with half window size. This helps when
the videos are larger than the screen size.
5.1.9

Object ID’s

The tool is ready to label different objects on the same image. To each object is assigned a different identification number (ID). The current ID can be
incremented or decremented using the “5” and “6” keys.
A label with an ID equal to the current ID has the color yellow or green
according to the label type (see subsection 5.2.2). The labels with other ID’s
are shown in gray.
Pressing the “x” key, the ID’s are all shown inside the labels they belong to
(Figure 5 and Figure 6d). By pressing “v” the currently selected ID is shown in
the top right corner of the image.
The commands only affect the label with the current ID. To create, modify
or delete a label with a different ID it is mandatory to first use the “5” and “6”
keys to select the correct ID.

5.2 Labels
5.2.1

Label anatomy

A label consists in a rectangle with four borders. The object should remain
inside the label and the label should be the smallest possible that fully contains
the object.
With this tool it is possible to move the label as a whole or to move its
borders independently.

9

(a) Final label.

(b) Temporary label.

(c) Temporary label (yellow) plus a la-

(d) A nal label (green, ID=0) with

bel with a dierent ID (gray).

a label for a dierent object (gray,
ID=1) with the ID's shown (press x
to show the ID's).

Figure 6: Label types.
5.2.2

Label types

There are two types of labels (see Figure 6):
• temporary labels - yellow color
• final labels - green color
When a label is created it’s type is by default temporary. This includes manually
(subsection 5.2.3) or automatically (subsection 5.3) created labels.
The labels will only become final when:
• are adjusted by the user (subsection 5.2.5)
• are marked by the user as final (subsection 5.2.6)
Note: It was tried to minimize the number of operations required per label.
For that purpose, several commands automatically mark the temporary labels
into final ones, avoiding the need for the user to do that explicitly. Is up to the
user to make sure that, in the end, all the necessary adjustments where in fact
applied to the final label.
5.2.3

Label creation

The labels can be created in two ways:
• manually - “+” key
10

(a) No selection (moves the whole la-

(b) Top border selected.

bel).

(c) Top border selected (mouse over

(d) Right border selected (mouse over

horizontal straight line).

vertical straight line).

(e) Two borders selected (mouse over
the corner).

Figure 7: Ways to use the mouse.
• automatically - see 5.3
When created manually, the label is by default placed near the top left corner
of the image. The user should then move the label to the right place and adjust
its borders using the keyboard or the mouse.
Tip: in this case (manual creation) it is probably better to first use the
mouse to do a coarse adjustment and after use the keyboard (and zoom) for fine
adjustments.
5.2.4

Label deletion

Press SHIFT + “+” (i.e., “*” key) to delete the current label.
5.2.5

Label modification

Using the mouse The mouse can be used to move the label or its borders by
means of click, drag and release. The point in the image where the user clicks
before dragging defines the operation realized by the mouse.
Moving the label border using the mouse By pressing the mouse over a
border or over the straight line the extends the border will that border will be
moved. The selected border or borders will be shown in red color.
11

Pointing the mouse over the straight line that extends the border (but outside
the border) is useful when the label is too small and is difficult to point to the
border directly.
It is also possible to move two borders simultaneously by pointing the mouse
at the label corner where the borders intercept.
Moving the whole label using the mouse By pressing at any point that
does not select any border, the label is moved as an whole without changing its
dimensions.
Moving the label border using the keyboard There are independent
keys to move each of the borders and in each direction (see Figure 2). The keys
disposition is organized in a logic way in what concerns the border position and
the movement direction.
For example, both keys that move the left border (“a” and “s”) are on the
left side in relation to the other keys. In addition, the “a” key which is on the
left side moves the border to the left and the “s” key which moves the border to
the right is on the right side. Hopefully, this layout is intuitive enough so that
the user can adjust the label without needing to look at the keyboard.
The user can even move the border faster, 10 pixels at a time, by simultaneously pressing the SHIFT key with the movement keys.
Moving the whole label using the keyboard There are no specific keys
to move the label as a whole. However, that effect is easily achieved using the
same keys that move the borders.
Suppose that the user intents to move the label sideways to the left. This is
the same as moving both left and right borders to the left by the same ammount.
We can then use the “a” and “f” keys and press them rapidly one after the other
and get the movement desired. Better yet, in most cases (depending on the
keyboard hardware) we can even press them simultaneously since the keyboard
will still send the two keystrokes one after the other (the ordering does not
matter).
This technique even works if we keep pressing the SHIFT key, allowing for
large movements of the whole label, 10 pixels each time.
5.2.6

Finalizing the labels

As mentioned before, the labels are created with type equal to temporary. This
always happens either for manually or for automatically created labels. Is up
for the user to verify all labels, adjust as necessary and then tag the labels as
final.
For work optimization purposes, it was tried to minimize the number of keys
that is necessary to press for each label. Towards that purpose, some operations,
namely the ones that move the label or its borders, automatically set the label
type to final. It is assumed that if the operator adjusted the label then it is
already final or is in the process of becoming final. It is up to the user to make
sure that all necessary adjustments are in fact made.
If no adjustment whatsoever is necessary, the the label can be set to final by
pressing SIFT + “t”.

12

Pressing in “t” only (without SHIFT) sets the label as temporary again.
There is yet the ENTER key which sets the current label as final and seeks
to the next frame. This combination is useful when reviewing many labels (for
example, after applying the automatic methods of subsection 5.3). Probably in
that case, many of the labels do not need adjustment and suffices to mark them
as final and go to the next frame, and for all that the user only needs to press
ENTER.

5.3 Automations
One way to alleviate the task of labeling is to use the available automations that,
even though do not intend to replace the manual labeling, they can assist into
making it easier. Four automatic methods are available, two of which operate
image by image while the other two operate for a set of images in one step.
These methods are described next.
5.3.1

Copy

Press the “p” key.
This command copies the label of the previous frame to the current frame.
The previous frame label needs to exist and be final, otherwise the command
does nothing.
Assuming that the objects move very little from frame to frame, it is faster
to copy the previous label and do small adjustments then to create a label from
the start for every frame.
5.3.2

Copy with search

Press the “o” key.
This command is identical to the previous one but, after copying the previous
frame label, also searches, in the current frame and in the neighborhood of the
copied label, for the image contained in the original label. The search is based
on the minimization of the quadratic error between the two images. Finally, the
position of the label is adjusted to the position where the error was smaller.
In most cases this approach produces very good labels only requiring occasional small adjustments.
5.3.3

Linear interpolation

In this method two non contiguous frames are manually labeled and then linear
interpolation is used to estimate the labels of the frames in the middle. See the
example in Figure 8.
To use this method the following steps are required:
1. create and finalize the label in the first frame of the interval
2. create and finalize the label in the last frame of the interval
3. seek to the last frame of the interval
4. press the “i” key

13

Figure 8: Example of labels obtained automatically using linear interpolation
between frames 0 and 100. The labels at the extremes (frames 0 to 100, green
color) where defined manually. The others (yellow) where interpolated.
By pressing “i”, the method goes backward in the video until it finds the previous
final label. Then it does an linear interpolation between that label and the
current frame label, either creating temporary labels for the frames in between
or changing them if they already existed.
This method applies well to cases where the object moves along a line in
the image. Many of the movements found are linear or can be approximated by
smaller linear sections. Using this method, together with the following method
(subsection 5.3.4), allows the user to automatically obtain very good approximations to the movement of the object, minimizing the number of manual
adjustments necessary.
5.3.4

Search in a sequence

This method adjusts the temporary labels previously defined (for example, by
the previous method - subsection 5.3.3) in a set of frames between two final
labels also previously defined. See example in Figure 9.
To use this method the following steps are necessary:
1. create the final labels at the two extremes of the frame set
2. create the temporary labels inside the set
3. seek to the frame at the extreme end of the set
4. press the “u” key

14

Figure 9: Labels obtained after applying the search in a sequence method (compare with the previous figure).
By pressing “u”, the method goes back in the video until it finds a final label,
thus defining the frame where the set starts. Then it saves the images inside
the labels at the extremes of the set.
For each frame within the set, the method searches in the neighborhood of
the temporary label of this frame for the two images saved. The search is based
on the minimization of the quadratic image error, similar to subsection 5.3.2,
but now two errors are obtained, one for each image. The errors are weighted
according to the temporal distance between the current frame and the frames of
the two saved images and then the lowest one is chosen. The current temporary
label is then adjusted accordingly to the position found for the image chosen.
The weighting of the error based on time distance is justified by the assumption that the closer the images, the similar they should be. Using the
two images at the extremes together with this weight allows for the method to
work in larger sets with larger time intervals, even if the image of the object
varies in those intervals (for example, the object can rotate, change size due to
perspective, illumination can change, etc.).
This method is well suited to be used with the previous method (subsection 5.3.3) since it compensates well for deviations of the object from the linear
trajectory. Frequently the object’s trajectory is not exactly linear. This can
happen because the trajectory is in fact not linear (for example, if it is circular) but can also happen due to factors external to the object, such as camera
vibrations or other camera movements.
This method was applied with great success to video sequences with up to
500 frames in a single step.

15

5.4 Label conrmation and verication
Note that none of this automatic methods eliminate need for the manual verification by the user (frame by frame) of the labels estimated automatically.
In fact, the labeling tool marks those labels as temporary forcing the user to
go by all of them to manually verify, adjust and set them as final. However,
these methods obtain very good, and in many cases correct, labels for a large
number of frames. By using them, the user only has to do occasional small
adjustments and confirm the labels that are already correct. See how in subsections 5.2.5 and 5.2.6.

5.5 Visual Help
5.5.1

Dynamic range maximization

By pressing the “1” key the dynamic range on the luminance of the current
image show on screen is maximized. This option determines the maximum and
minimum values of the image’s luminance and scales it so that all available
dynamic range of the screen is used.
This functionality is useful when the images have very low contrast and the
object is not easy to be seen.
This luminance scaling is only visual and does not affect the automatic methods of section 5.3, which continue to use the original (non scaled) luminance.
Pressing again the “1” key disables this feature.

16


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Author                          : Ricardo Ribeiro (ribeiro@isr.ist.utl.pt)
Title                           : Labeling Tool - User Manual
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