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* Applied changes suggested by reviewer #1:

-Page 3:
    The Latex "\noindent" could be added
    after equations (1) and (2).
    -Page 3, paragraph 3:
    gaussian -> Gaussian
    -Page 3 (two times):
    Experiment shows -> Experiments show  ??


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2008-displacement/paper/paper.tex Näytä tiedosto

@@ -101,7 +101,7 @@ value based on that model. One such algorithm is direct binary seach (DBS)
(LSMB) \cite{lsmb}.

HVS models are usually low-pass filters. Nasanen \cite{nasanen}, Analoui
and Allebach \cite{allebach} found that using gaussian models gave visually
and Allebach \cite{allebach} found that using Gaussian models gave visually
pleasing results, an observation confirmed by independent visual perception
studies \cite{mcnamara}.

@@ -140,8 +140,8 @@ mean square error between modified versions of the images, in the form:
E(h,b) = \frac{(||v * h_{i,j} - v * b_{i,j}||_2)^2}{wh}
\end{equation}

where $w$ and $h$ are the image dimensions, $*$ denotes the convolution and $v$
is a model for the human visual system.
\noindent where $w$ and $h$ are the image dimensions, $*$ denotes the
convolution and $v$ is a model for the human visual system.

To compensate for the slight translation experienced in the halftone, we
use the following error metric instead:
@@ -150,10 +150,10 @@ use the following error metric instead:
E_{dx,dy}(h,b) = \frac{(||v * h_{i,j} - v * t_{dx,dy} * b_{i,j}||_2)^2}{wh}
\end{equation}

where $t_{dx,dy}$ is an operator which translates the image along the $(dx,dy)$
vector.
\noindent where $t_{dx,dy}$ is an operator which translates the image along the
$(dx,dy)$ vector.

A simple example can be given using a gaussian HVS model:
A simple example can be given using a Gaussian HVS model:

\begin{equation}
v(x,y) = e^{\frac{x^2+y^2}{2\sigma^2}}
@@ -165,7 +165,7 @@ Finding the second filter is then straightforward:
(v * t_{dx,dy})(x,y) = e^{\frac{(x-dx)^2+(y-dy)^2}{2\sigma^2}}
\end{equation}

Experiment shows that for a given image and a given corresponding halftone,
Experiments show that for a given image and a given corresponding halftone,
$E_{dx,dy}$ has a local minimum almost always away from $(dx,dy) = (0,0)$ (Fig.
\ref{fig:lena-min}). Let $E$ be an error metric where this remains true. We
call the local minimum $E_{min}$:
@@ -178,7 +178,7 @@ call the local minimum $E_{min}$:
\begin{center}
\input{lena-min}
\caption{Mean square error for the \textit{Lena} image. $v$ is a simple
$11\times11$ gaussian convolution kernel with $\sigma = 1.2$ and
$11\times11$ Gaussian convolution kernel with $\sigma = 1.2$ and
$(dx,dy)$ vary in $[-1,1]\times[-1,1]$.}
\label{fig:lena-min}
\end{center}
@@ -190,7 +190,7 @@ taking the displacement into account, the error becomes $7.77\times10^{-4}$
for $(dx,dy) = (0.167709,0.299347)$. The new, corrected error is significantly
smaller, with the exact same input and output images.

Experiment shows that the corrected error is always noticeably smaller except
Experiments show that the corrected error is always noticeably smaller except
in the case of images that are already mostly pure black and white. The
experiment was performed on a database of 10,000 images from common computer
vision sets and from the image board \textit{4chan}, providing a representative
@@ -299,7 +299,7 @@ to be unstable \cite{stability}, and diffusing less than 100\% of the error is
known to cause important error in shadow and highlight areas of the image.

First we studied all possible coefficients on a pool of 250 images with an
error metric $E$ based on a standard gaussian HVS model. Since we are studying
error metric $E$ based on a standard Gaussian HVS model. Since we are studying
algorithms on different images but error values are only meaningful for a given
image, we chose a Condorcet voting scheme to determine winners. $E_{min}$ is
only given here as an indication and had no role in the computation:


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