I am reading a paper on seam carving to implement, and got stuck in understanding the convention used in the equation below.
1) I understand, $\{ ( x ( i ) , i ) \} _ { i = 1 } ^ { n } , \text { s.t. } \forall i , | x ( i ) - x ( i - 1 ) | \leq 1$ part, but unable to understand, why he calls them $\bf{s}^{\bf{x}}$. What does the author indicate here?
2) Also I did not understand the last line about mapping.
I tried to search for hours one whole day online, but could not find any thing to understand this notation. Kindly help. The stanza extends as below, but I could not find anything relevant under 8-connected path also as noted there.
By $s^x$, the author is making up a new shorthand meaning "this is a seam" (that's the letter "s") based on the sequence called $x$.
The $[1,\ldots n] \to [1, \ldots m]$ means a function from the set of integers $\{1, 2, 3, \ldots, n\}$ to the integers $\{1, 2, \ldots, m\}$.
So for a $4 \times 5$ image, $x$ is a function from $\{1,2,3, 4\}$ to $\{1,2,3,4,5\}$. The number $x(i)$ tells you, for row $i$, where in column $i$ the "seam" is passing.
It might be defined by, say $$ x(1) = 2\\ x(2) = 3\\ x(3) = 2\\ x(4) = 1 $$
Within a computer program, it'd probably be stored in an array:
int x[4].Drawing a picture, we have
where the pixels marked "p" are the ones described by the "seam data"
2, 3, 2, 1because they lie (reading top to bottom) in columns 2, then 3, then 2, then 1.In defining the sequence $s^x$, the author is trying to get at the following idea: for a sequence like $x$ (which is meant to indicate column-coordinates), you can make a sequence of pixel-coordinates that looks like this:
$$ sx(1) = (2, 1)\\ sx(2) = (3, 2)\\ sx(3) = (2, 3)\\ sx(4) = (1, 4) $$
This is slightly odd, because in the author's pixel coordinates, the ROW coordinate appears second, and the column coordinate appears first. That's probably an attempt to make it match the usual cartesian coordinates, in which we place x-coordinates first, and y-coordinates second.
Anyhow, that's what the author's trying to say.