isophote


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isophote

(ˈaɪsəˌfəʊt)
n
(Astronomy) astronomy a line on a diagram or image of a galaxy, nebula, or other celestial object joining points of equal surface brightness
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where u is the observed noisy image, sign is a sign function, and [u.sub.NN] is the second directional derivative of the image along a local normal direction to the isophote line.
The diffusion intensity is high when the curvature is large and decreases along with the isophote furtherly smoothing.
Let the unit coordinate vectors in the O-xy system be i and j, then, any point in the space could be expressed by a vector r=xi+yj, which becomes r=[xi]p+[eta]q in the O-[xi][eta] system, where [xi] and n are the two components in the isophote and gradient directions respectively, and p and q are the two orthogonal unit vectors:
By using third-order PDE model, the algorithm allows for the curvature of isophote lines.
Kim, "GA-based image restoration by isophote constraint optimization," EURASIP Journal on Advances in Signal Processing, vol.
Now, for a little more precision on the expected behaviour of [PSI](s), we decompose divergence part in terms of the tangent and normal directions to the isophote lines.
An image can be thought of as a collection of curves with equal value, the isophotes. At extrema an isophote reduces to a point, at saddle points the isophote is self-intersecting.
[4], who proposed a method in which the information is propagated in the occluded area, through isophote lines that cross the edges.
That is, we break it into the tangential (T) and normal (N) directions to the isophote lines.
By measuring the phase of Venus using such isophote contours on all three dates, I found a discrepancy of about 2 percent from prediction.
Valenti and Gevers [5] used the curvature of isophotes to design a voting system for eye and pupil localization.