Skip to content
Snippets Groups Projects
Commit 4e514645 authored by even's avatar even
Browse files

Article: intro revisited

parent d8df9740
No related branches found
No related tags found
No related merge requests found
...@@ -37,7 +37,7 @@ blurred segments of fixed width in gray-level images was already introduced. ...@@ -37,7 +37,7 @@ blurred segments of fixed width in gray-level images was already introduced.
It is based on a first rough detection in a local area It is based on a first rough detection in a local area
of the image either defined by the user in supervised context or blindly of the image either defined by the user in supervised context or blindly
explored in automatic mode. The goal is to disclose the presence of an edge. explored in automatic mode. The goal is to disclose the presence of an edge.
Therefore, a simple test as the gradient maximal value is performed. Therefore a simple test as the gradient maximal value is performed.
In case of success, refinement steps are run through an exploration of In case of success, refinement steps are run through an exploration of
the image in the direction of the detected edge. the image in the direction of the detected edge.
...@@ -48,25 +48,23 @@ untill a correct candidate with an acceptable gradient orientation is found. ...@@ -48,25 +48,23 @@ untill a correct candidate with an acceptable gradient orientation is found.
Only the gradient information is processed as it provides a good information Only the gradient information is processed as it provides a good information
on the image dynamics, and hence the presence of edges. on the image dynamics, and hence the presence of edges.
Trials to also use the intensity signal were made through costly correlation Trials to also use the intensity signal were made through costly correlation
techniques, but they were mostly successful for detecting objects with techniques, but they were mostly successful for detecting shapes with a
stable appearance such as metallic pipes \cite{AubryAl17}. stable appearance such as metallic tubular objects \cite{AubryAl17}.
Despite of good performances obtained compared to other methods from the Despite of good performances achieved, several drawbacks remain.
literature, several drawbacks remain. First, the blurred segment width is not measured but initially set by the
First, the blurred segment width is not measured, but initially set by the user according to the application requirements. The produced information
user to meet the application requirements, so that no quality information on the edge quality is rather poor, and especially when the edge is thin,
can be derived from the computed segment. the risk to incorporate outlier points is quite high, thus producing a
Moreover, the blurred segment hull is left free to shift sidewards, or worst, biased estimation of the edge orientation.
to rotate around a thin edge in the image, and the produced orientation
value can be largely biased.
Then, two refinement steps are systematically run to cope with most of the Then, two refinement steps are systematically run.
tested data, although this is useless when the first detection is successfull. On one hand, this is useless when the first detection is successfull.
Beyond, there is no guarantee that this could treat all kinds of data. On the other hand, there is no guarantee that this approach is able to
The search direction is fixed by the support vector of the blurred segment process larger images.
detected at the former step, and because the set of vectors in a bounded The search direction relies on the support vector of the blurred segment
discrete space is finite, there is necessarily a limit on this direction detected at the former step, and the numerization rounding fixes a limit
accuracy. on this estimated orientation accuracy.
It results that more steps would inevitably be necessary to process higher It results that more steps would inevitably be necessary to process higher
resolution images. resolution images.
...@@ -83,10 +81,10 @@ As a side effect, these two major evolutions also led to a noticeable ...@@ -83,10 +81,10 @@ As a side effect, these two major evolutions also led to a noticeable
improvement of the time performance of the detector. improvement of the time performance of the detector.
In the next section, the main theoretical notions this work relies on are In the next section, the main theoretical notions this work relies on are
introduced, with a specific focus on the new concept of adaptive directional introduced.
scanner. Then the new detector workflow, the adaptive directional scanner, the control
Then the new detector workflow and its integration into both supervised and of the assigned with and their integration into both supervised
unsupervised contexts are presented and discussed in \RefSec{sec:method}. and unsupervised contexts are presented and discussed in \RefSec{sec:method}.
Experiments led to assess the expected increase of performance are decribed Experiments led to assess the expected increase of performance are decribed
in \RefSec{sec:expe}. in \RefSec{sec:expe}.
Finally achieved results are summarized in \RefSec{sec:conclusion}, Finally achieved results are summarized in \RefSec{sec:conclusion},
......
...@@ -267,7 +267,7 @@ This distinction is illustrated on \RefFig{fig:edgeDir}. ...@@ -267,7 +267,7 @@ This distinction is illustrated on \RefFig{fig:edgeDir}.
Another option, called multi-detection allows the detection of all the Another option, called multi-detection allows the detection of all the
segments crossed by the input stroke $AB$. segments crossed by the input stroke $AB$.
The multi-detection algorithm is displayed below. The multi-detection algorithm (Algorithm 1) is displayed below.
\input{Fig_method/algoMulti} \input{Fig_method/algoMulti}
...@@ -282,6 +282,7 @@ detected blurred segments $\mathcal{B}_j''$ at the end of each successful ...@@ -282,6 +282,7 @@ detected blurred segments $\mathcal{B}_j''$ at the end of each successful
detection; detection;
iii) points marked as occupied are rejected when selecting candidates for the iii) points marked as occupied are rejected when selecting candidates for the
blurred segment extension in the fine tracking step. blurred segment extension in the fine tracking step.
Multiple detections of the same edge are thus avoided.
In edge selection mode (\RefFig{fig:edgeDir} b), the multi-detection In edge selection mode (\RefFig{fig:edgeDir} b), the multi-detection
algorithm is executed twice. algorithm is executed twice.
...@@ -341,7 +342,8 @@ segment. ...@@ -341,7 +342,8 @@ segment.
\subsection{Automatic blurred segment detection} \subsection{Automatic blurred segment detection}
An unsupervised mode is also proposed to automatically detect all the An unsupervised mode is also proposed to automatically detect all the
straight edges in the image. A stroke that crosses the whole image, is straight edges in the image. The principle of this automatic detection
is described in Algorithm 2. A stroke that crosses the whole image, is
swept in both direction, vertical then horizontal, from the center to swept in both direction, vertical then horizontal, from the center to
the borders. At each position, the multi-detection algorithm is run the borders. At each position, the multi-detection algorithm is run
to collect all the segments found under the stroke. to collect all the segments found under the stroke.
......
...@@ -67,7 +67,7 @@ DS = \left\{ S_i = \mathcal{D} \cap \mathcal{N}_i \cap \mathcal{I} ...@@ -67,7 +67,7 @@ DS = \left\{ S_i = \mathcal{D} \cap \mathcal{N}_i \cap \mathcal{I}
\end{array} \right. \right\} \end{array} \right. \right\}
%S_i = \mathcal{D} \cap \mathcal{N}_i, \mathcal{N}_i \perp \mathcal{D} %S_i = \mathcal{D} \cap \mathcal{N}_i, \mathcal{N}_i \perp \mathcal{D}
\end{equation} \end{equation}
In this expression, the clause In this definition, the clause
$\delta(\mathcal{N}_i) = - \delta^{-1}(\mathcal{D})$ $\delta(\mathcal{N}_i) = - \delta^{-1}(\mathcal{D})$
expresses the othogonality constraint between the scan lines $\mathcal{N}_i$ expresses the othogonality constraint between the scan lines $\mathcal{N}_i$
and the scan strip $\mathcal{D}$. and the scan strip $\mathcal{D}$.
...@@ -79,7 +79,7 @@ The scans $S_i$ are developed on each side of a start scan $S_0$, ...@@ -79,7 +79,7 @@ The scans $S_i$ are developed on each side of a start scan $S_0$,
and ordered by their distance to the start line $\mathcal{N}_0$ with and ordered by their distance to the start line $\mathcal{N}_0$ with
a positive (resp. negative) sign if they are on the left (resp. right) a positive (resp. negative) sign if they are on the left (resp. right)
side of $\mathcal{N}_0$ (\RefFig{fig:ds}). side of $\mathcal{N}_0$ (\RefFig{fig:ds}).
The directional scan is iterately processed from the start scan to both ends. The directional scan is iterately parsed from the start scan to both ends.
At each iteration $i$, the scans $S_i$ and $S_{-i}$ are successively processed. At each iteration $i$, the scans $S_i$ and $S_{-i}$ are successively processed.
\begin{figure}[h] \begin{figure}[h]
...@@ -111,9 +111,11 @@ At each iteration $i$, the scans $S_i$ and $S_{-i}$ are successively processed. ...@@ -111,9 +111,11 @@ At each iteration $i$, the scans $S_i$ and $S_{-i}$ are successively processed.
\put(-60,30){$\mathcal{N}_8$} \put(-60,30){$\mathcal{N}_8$}
\put(-169,8){$\mathcal{N}_{-5}$} \put(-169,8){$\mathcal{N}_{-5}$}
\end{picture} \end{picture}
\caption{A directional scan: the start scan $S_0$ in blue, odd scans in \caption{A directional scan.
green, even scans in red, scan lines bounds $\mathcal{N}_i$ in The start scan $S_0$ is drawn in blue, odd scans in green,
plain lines and scan strip bounds $\mathcal{D}$ in dotted lines.} even scans in red, the bounds of scan lines $\mathcal{N}_i$
with plain lines and the bounds of scan strip $\mathcal{D}$
with dotted lines.}
\label{fig:ds} \label{fig:ds}
\end{figure} \end{figure}
......
0% Loading or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment