Homographies , Image Mosaics and Tracking. Assignment 1. Homography estimation from corresponding points Homographies describe image transformation of... General scene when camera motion is rotation about camera center Planar surfaces under general camera motion
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Homographies,
Image Mosaics and Tracking
Assignment 1
Goal: Stitch together several images into a seamless composite
h(x)
x
x’
f(x)
g(x’)
h(x)
x
x’
f(x)
g(x’)
h(x)
x
x’
f(x)
g(x’)
x
x’
f(x)
g(x’)
Round-off idea: Just use closest integer-valued pixel
Problem is that it can cause big aliasing effects
Why? Because the round() function causes discontinuous switches in which pixel is nearest and hence is the color drawn
rotate 45±, scale 1.5
t controls “blend”
of two endpoints
p(t) = p0 + t(p1 ¡ p0), wheret2[0, 1]
= p0¡tp0 + tp1
= (1 ¡ t)p0 + tp1
from Akenine-Möller & Haines
Vertical blend
Horizontal blend
Blending eliminates abrupt color changes, reducing aliasing artifacts
rotate 45±, scale 1.5
courtesy of P. Haeberli
+
=
1
0
1
0
0
1
0
1
left
right
0
1
0
1
0
1
=
Demo
[Brown & Lowe, ICCV’03]