标题: An Interactive Augmented Reality Coloring Book [打印本页] 作者: 彬彬 时间: 2011-12-21 09:30 标题: An Interactive Augmented Reality Coloring Book Adrian Clark1, Andreas Dünser1, Raphaël Grasset1,2
1The HIT Lab NZ, University of Canterbury, Christchurch, New Zealand
2Institute for Computer Graphics and Vision, Graz University of Technology, Austria
INTRODUCTION
Creating entertaining and educational books not only
requires providing visually stimulating content but also
means for students to interact, create, and express
themselves.
We present a new type of mixed-reality book experience,
which augments an educational coloring book with usergenerated
three dimensional content. In particular, we
introduce a new technique to engage users in actively
creating AR book content in real time using a coloring book
metaphor. In this first prototype, users can color the pages
of the book, and the system automatically recognizes the
pages and the various colors used by the users, and directly
maps the colored end results to virtual pop-up scenes and
3D models.
Our system is based on natural feature tracking and image
processing techniques that can be easily exploited for other
AR publishing applications.
SYSTEM DESIGN
A natural feature registration approach was chosen to
support the augmentation and modification of a physical
book. To allow modification of the content of the book, the
registration needed to be sufficiently robust to changing
targets. As even a small change in the original image can
cause registration failure, a series of filters were applied to
remove as much color as possible from each frame.
For each frame of video, the image contrast was
maximized while ensuring color constancy, and then white
balanced. The distance was calculated for each pixel from a
line between black and a predefined maximum gray value a
pixel can have which is still considered black. The final step
of color removal was to threshold all distances above a
given value to the color white. The final result is shown in
Figure 1.
Figure 1. Left: Original Image. Right: After Color Removal
Once the color has been removed from the frame, it can
be registered against known pages. To maximize robustness
and speed, the OPIRA registration library [1] was used in
conjunction with the SURF [2] feature detector.
When the black and white page is successfully registered,
the frame is rectified to the same orientation and dimensions
as the image of the page which was used for registration,
and the texture extracted. The page detection registration
process is stopped, and a new registration process for
tracking the rectified colored page is started.
EXAMPLE APPLICATION
The New Zealand Department of Conservation issues a
coloring book titled “Amazing Animals of New Zealand” to
primary school aged children to teach children about
animals native to New Zealand. Two pages of the book
were given to five children aged between 6 and 8 years old
to color in, and their colored pages were used as examples
for the application.
Color masks were created for each page, where every area
designed to pop up as a virtual image layer was colored in a
separate color. When the a frame is captured an alphablended
texture is created for each color. The background
texture is filled with the original image, such that when the
layers “pop-up” it appears the color has lifted off the page.
Every other texture is filled with the rectified image
captured at the end of the registration process.
Animated models were created for the most important
object in the scene, in the two examples, a Kiwi and a
Penguin. These models were texture mapped using the
original pages as the reference. When the page is detected,
the relevant area of the image is copied into the models
texture buffer, such that the model is now textured using the
image on the page. Example images are shown in Figure 2.
Figure 2. Screen shots from the Example Application
CONCLUSION
This work presents a new experience utilizing augmented
reality enhanced books where users are able to color in the
pages, and these pages are recognized by the system and
used to produce three dimensional scenes and textured
models reflecting the artwork created by the users.
The color removal system developed is able to
successfully allow automatic registration and texture
extraction from coloring book pages, even when the images
appear significantly different from the unmodified black and
white pages. The system was capable of running at real-time
frame rates, and with accuracy comparable to capturing the
images offline.
REFERENCES
[1] Clark, A., Green, R. and Grant, R.: 2008, “Perspective
correction for improved visual registration using natural
features”, Image and Vision Computing New Zealand,
2008. IVCNZ 2008. 23rd International Conference,
pages 1-6
[2] Bay, H.; Ess, A.; Tuytelaars, T.; Van Gool, L. "SURF:
