image

Preface
Images contain information about the spatial properties of the scene they depict.
When coupled with suitable assumptions, images can be used to infer three-
dimensional information. For instance, if the scene contains objects made with
homogeneous material, such as marble, variations in image intensity can be as-
sociated with variations in shape, and hence the “shading” in the image can be
exploited to infer the “shape” of the scene (shape from shading). Similarly, if the
scene contains (statistically) regular structures, variations in image intensity can
be used to infer shape (shape from textures). Shading, texture, cast shadows, oc-
cluding boundaries are all “cues” that can be exploited to infer spatial properties
of the scene from a single image, when the underlying assumptions are satis-
fied. In addition, one can obtain spatial cues from multiple images of the same
scene taken with changing conditions. For instance, changes in the image due to

a moving light source are used in “photometric stereo,” changes in the image due
to changes in the position of the cameras are used in “stereo,” “structure from
motion,” and “motion blur.” Finally, changes in the image due to changes in the
geometry of the camera are used in “shape from defocus.” In this book, we will
concentrate on the latter two approaches, motion blur and defocus, which are
referred to collectively as “accommodation cues.” Accommodation cues can be
exploited to infer the 3-D structure of the scene as well as its radiance proper-
ties, which in turn can be used to generate better quality novel images than the
originals.
Among visual cues, defocus has received relatively little attention in the lit-
erature. This is due in part to the difficulty in exploiting accommodation cues:
the mathematical tools necessary to analyze accommodation cues involve con-
tinuous analysis; unlike stereo and motion which can be attacked with simple

About AnhTuan

Giáo Viên Tiếng Anh tại Buôn Ma Thuột-Đăklăk

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