International Conference on Artificial Reality and TelexistenceEurographics Symposium on Virtual Environments (2016)
D. Reiners, D. Iwai, and F. Steinicke (Editors)

Automatic Display Zoom Using Face Size of Camera Image
Yuki Satale1 , Kenji Funahashi1
1 Nagoya Institute of Technology, Nagoya, Japan

Abstract
When it is hard to see a small font size document that is in your hand, you usually move it closer to your face. When you want
to see the whole of a large sheet such as a map, you usually get it away from your face. On the other hand when you get into asame situation on a PC screen and tablet device, you zoom it using a mouse or doing pinch operation. So we consider zooming
display appropriately referring the distance between a face and a screen also when using PC and tablet. If the distance value
is mapped to the zoom scale parameter directory, it always changes according to the slight change of the posture. Therefore
the presence or absence of the scale change is determined from the distance change in a predefined period. In this paper, we
propose corresponding about the distance change and scaling, also described for the experimental system in order to confirm
the validity of this idea.
Categories and Subject Descriptors (according to ACM CCS): H.5.2 [INFORMATION INTERFACES AND PRESENTATION(e.g., HCI)]: User Interfaces—Interaction styles (e.g., commands, menus, forms, direct manipulation)

1. Introduction
When it is hard to see a small font size document that is in yourhand, you usually move it closer to your face. When you want to
see the whole of a large sheet such as a map, you usually get it awayfrom your face. On the other hand when you get into a same situation on a PC screen and tablet device, you zoom it using a mouse or
doing pinch operation [Wel91] [GWF95]. So we consider zooming
display appropriately referring the distance between a face and ascreen also when using PC and tablet. There is a related work, thatrealizes stereoscopic viewing with motion parallax by recognizing
the face position [Fra11]. If the distance value is mapped to thezoom scale parameter directory, it always changes according to theslight change of the posture. Therefore the presence or absence ofthe scale change is determined from the distance change in a predefined period. In this paper, we propose for the relation of this scale
and the distance, then describe the pilot system in order to confirm
the validity of this idea.
2. Scaling determined to face distance
Although it is conceivable to use a range sensor for measuring the
distance between a face and a screen, we use a image camera thatcan be easily prepared. In the case of a PC, a web camera is put at
the top of the monitor. In the case of a laptop or tablet, the built-in
camera of the screen side is used. First a face area is recognizedusing the OpenCV library from the captured image. The height:
h(t) and width: w(t) of the face area are obtained at the time: t(figure1), it should be noted the face is assumed to be upright. In
order to avoid the influence of a camera noise and a recognitionc 2016 The Author(s)Eurographics Proceedings c 2016 The Eurographics Association.

Figure 1: Height and width of faceerror, the average values H(t) and W (t) are obtained in a predefined
period. This period D is F/ f (sec), where F is determined as 6
frame empirically for f = 30 frame/sec processing speed. Next, theaverage H(t) is compered with H(t − D) . The average W (t) is also
compered (Formula1).
H ′ (t) = H(t) − H(t − D)W ′ (t) = W (t) −W (t − D)

(1)Those values are possibly affected by a slight change of the posturefor example sitting up again. So the display is zoomed in as s withsmooth animation effect in period D,e
W ′ (t)H ′ (t)s=+(2)
2 H(t − D) W (t − D)when the change is more than c1 (×100[%]) and less than c2 ;c1 <H ′ (t)< c2
H(t − D)

Yuki Satake & Kenji Funahashi / Automatic Display Zoom Using Face Size of Camera Image

Figure 2: Average and comparison of hightc1 <W ′ (t)< c2 .
W (t − D)(3)

Or the display is zoomed out as −s with animation effect, when thechange is more than c1 and less than c2 ;c1 < −
c1 < −H ′ (t)< c2
H(t − D)W ′ (t)< c2 ,W (t − D)(4)

where c1 , c2 and e are positive value, and are set as c1 = 0.05,
c2 = 0.5, and e = 1.0 empirically.
3. Experiments and results
We used desktop PC and web camera to develop the system weproposed. The OpenCV library was used to recognize a face. The
camera was set under the display for the experiment. The systemappearance is shown in Figure3. Figure 4 shows the flow that theperson moved away from the display then moved closer to the display, and the map image was zoomed out and in.

Figure 4: Display zoomed according to the distance
Figure 3: System appearance

References
4. Conclusion
In this paper we proposed new approach to zoom display appropriately referring the distance between a face and a screen whenusing PC. When you moving closer to display, it is zoomed in.
Getting away from display, it is zoomed out to see the whole. It
is expected to improve the operability to zoom. In the future, weshould implement this proposed model to a tablet device to verify
the effectiveness of this idea. The empirical parameters should bealso considered and determined.

[Fra11] F RANCONE J.: Laurence nigay, using the user’s point of viewfor interaction on mobile devices. Proceedings of the 23th ACM International Conference of the Association Francophone d’Interaction
Homme-Machine (IHM2011) (2011), p.p.25–31. 1[GWF95] G EORGE W. F ITZMAURICE H IROSHI I SHII W. A. S. B.:
Bricks: laying the foundations for graspable user interfaces. Proceedings of the CHI ’95 (1995), 442–449. 1[Wel91] W ELLNER P.: The digitaldesk calculator: tangible manipulation
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c 2016 The Author(s)Eurographics Proceedings c 2016 The Eurographics Association.